A METHOD OF FABRICATING A MEMBRANE FOR WASTE WATER TREATMENT

Abstract

An ecofriendly method of fabricating a membrane for waste water treatment is disclosed. Said method broadly comprises following steps: soaking a powder of Sterculia foetida shells in a sodium hydroxide and sodium sulphide mixture to obtain lignin; dissolving polyvinyl alcohol in dimethylsulfoxide to obtain a mixture; stirring the mixture to obtain a solution; adding the lignin to the solution, followed by stirring overnight to obtain a homogenised solution; and casting and solidifying the homogenised solution, followed by drying to obtain the lignin membrane. The disclosed method of fabrication offers at least the following advantages and effects: is cost-effective; is eco-friendly (is plant-based); reduced process times; improved efficiency; is efficient in removing a broad spectrum of chemical dyes and heavy metals; and/or is reusable, with a high reusability efficiency.

Specification

Description:TITLE OF THE INVENTION: A METHOD OF FABRICATING A MEMBRANE FOR WASTE WATER TREATMENT
FIELD OF THE INVENTION
The present disclosure is generally related to waste water treatment. Particularly, the present disclosure is related to industrial waste water treatment. More particularly, the present disclosure is related to: method of fabricating a membrane for waste water treatment.
BACKGROUND OF THE INVENTION
Conventional methods and/or techniques for treating waste water include, physical treatments such as screening and sedimentation; chemical treatments such as coagulation and flocculation; biological treatments; and thermal treatments such as incineration and chemical precipitation.
However, such methods and/or techniques suffer from various drawbacks, including, but not limited to: high costs; creation of toxic byproducts, resulting in serious environmental pollution; extensive energy consumption; high process times; limited effectiveness; and/or require multiple membranes for removal of different chemical dyes and heavy metals.
There is, therefore, a need in the art, for: a method of fabricating a membrane for waste water treatment, which overcomes the aforementioned drawbacks and shortcomings.
SUMMARY OF THE INVENTION
An ecofriendly method of fabricating lignin membrane for waste water treatment is disclosed. Said method broadly comprises following steps:
A powder of Sterculia foetida shells is soaked in a sodium hydroxide and sodium sulphide mixture to obtain lignin. Ratio of said sodium hydroxide to said sodium sulphide is about 4.1:1.
Polyvinyl alcohol is dissolved in dimethylsulfoxide to obtain a mixture. Said mixture is stirred at about 90ºC to obtain a solution. The lignin is added to the solution, followed by stirring overnight, at about 60ºC, to obtain a homogenised solution. Ratio of said lignin to said polyvinyl alcohol is about 70:30.
The homogenised solution is casted and homogenised, for about 4 hours at about 20ºC, followed by drying at about 60ºC to obtain the lignin membrane.
The disclosed method of fabrication offers at least the following advantages and effects: is cost-effective; is eco-friendly (is plant-based); reduced process times; improved efficiency; is efficient in removing a broad spectrum of chemical dyes and heavy metals; and/or is reusable, with a high reusability efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A illustrates a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 1B illustrates results of scanning electron microscopy analyses, in accordance with an embodiment of the present disclosure;
Figure 1C illustrates a contact angle image of a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 2A and Figure 2B illustrate results of X-ray diffraction and tensile strength analyses, respectively, of a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 3 and Figure 4 illustrate results of thermogravimetric and differential scanning calorimetry analyses, respectively, of a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 5A and Figure 5B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 6A and Figure 6B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 7A and Figure 7B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 8A, Figure 8B, and Figure 8C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for methylene blue removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 8D illustrates results of thermodynamic parameter analyses, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 9A and Figure 9B illustrate results of pH and adsorbent dosage effect analyses, respectively, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 10A illustrates results of desorption rate analyses, at different concentrations, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 10B illustrates results of reusability analyses, for methylene blue removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 11A and Figure 11B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 12A and Figure 12B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 13A and Figure 13B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 14A, Figure 14B, and Figure 14C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for congo red removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 14D illustrates results of thermodynamic parameter analyses, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 15A and Figure 15B illustrate results of pH and adsorbent dosage effect analyses, respectively, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 16A illustrates results of desorption rate analyses, at different concentrations for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 16B illustrates results of reusability analyses, for congo red removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 17A and Figure 17B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 18A and Figure 18B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 19A and Figure 19B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 20A, Figure 20B, and Figure 20C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for crystal violet removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 20D illustrates results of thermodynamic parameter analyses, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 21A and Figure 21B illustrate results of pH and adsorbent dosage effect analyses, respectively, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 22A illustrates results of desorption rate analyses at different concentrations, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 22B illustrates results of reusability analyses, for crystal violet removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 23A and Figure 23B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 24A and Figure 24B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 25A and Figure 25B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 26A, Figure 26B, and Figure 26C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for brilliant green removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 26D illustrates results of thermodynamic parameter analyses, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 27A and Figure 27B illustrate results of pH and adsorbent dosage effect analyses, respectively, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 28A illustrates results of desorption rate analyses at different concentrations, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 28B illustrates results of reusability analyses, for brilliant green removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 29A and Figure 29B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 30A and Figure 30B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 31A and Figure 31B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 32A, Figure 32B, and Figure 32C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for chromium removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 32D illustrates results of thermodynamic parameter analyses, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 33A and Figure 33B illustrate results of pH and adsorbent dosage effect analyses, respectively, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 34A illustrates results of desorption rate analyses at different concentrations, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 34B illustrates results of reusability analyses, for chromium removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 35A and Figure 35B illustrate results of linear and non-linear Langmuir isotherm analyses, respectively, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 36A and Figure 36B illustrate results of Freundlich and Temkin isotherm analyses, respectively, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 37A and Figure 37B illustrate results of pseudo first-order kinetics and intraparticle diffusion analyses, respectively, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 38A, Figure 38B, and Figure 38C illustrate results of temperature studies fitted in the linear Langmuir isotherm, for cobalt removal, through a fabricated membrane, at 25ºC, at 35ºC, and at 45ºC, respectively, in accordance with an embodiment of the present disclosure;
Figure 38D illustrates results of thermodynamic parameter analyses, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 39A and Figure 39B illustrate results of pH and adsorbent dosage effect analyses, respectively, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure;
Figure 40A illustrates results of desorption rate analyses at different concentrations, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure; and
Figure 40B illustrates results of reusability analyses, for cobalt removal, through a fabricated membrane, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the words "comprise" and "include", and variations, such as "comprises", "comprising", "includes", and "including", may imply the inclusion of an element (or elements) not specifically recited. Further, the disclosed embodiments may be embodied, in various other forms, as well.
Throughout this specification, the use of the word "synthesis", and its variations, is to be construed as: "produce; manufacture; and/or the like".
Throughout this specification, the use of the word "fabricate", and its variations, is to be construed as: "produce; manufacture; and/or the like".
Throughout this specification, the use of the word "membrane" is to be construed as: "a lignin membrane that is fabricated from Sterculia foetida shells" (may also to be referred to as "fabricated membrane").
Throughout this specification, the use of the phrase "waste water" is to be construed as being inclusive of: waste water from industrial plants, sewage treatment plants, and agricultural operations that contains wide range of pollutants, including heavy metals and chemical dyes".
Throughout the specification, the use of the acronym "PVA" is to be construed as: "Poly Vinyl Alcohol".
Throughout the specification, the words "sulphur" and "sulfur" are used interchangeably.
Throughout this specification, the disclosure of a range is to be construed as being inclusive of: the lower limit of the range; and the upper limit of the range.
Throughout this specification, the words "the" and "said" are used interchangeably.
Also, it is to be noted that embodiments may be described as a method. Although the operations, in a method, are described as a sequential process, many of the operations may be performed in parallel, concurrently, or simultaneously. In addition, the order of the operations may be re-arranged. A method may be terminated, when its operations are completed, but may also have additional steps.
A method of fabricating a lignin membrane (may also be referred as "membrane") for waste water treatment is disclosed. The disclosed membrane was fabricated (or synthesised) as follows:
Material Preparations
Sterculia foetida shells were collected from SASTRA University Campus, Thanjavur, Tamil Nadu, India. About 1 kg of said Sterculia foetida shells (may also be referred as "shells") was washed, dried, and powdered to obtain a fibrous powder biomass, with a size of about 1 mm.
About 1 g of the obtained powder was soaked in an alkaline mixture comprising about 0.284 g sodium hydroxide and about 0.0692 g sodium sulphide (a ratio of about 4.1:1 between the sodium hydroxide to the sodium sulphide) to obtain lignin. Said alkaline mixture had an effective alkalinity of about 25% and a sulphidity of about 20%.
Fabrication of the Membrane
About 0.9 g of polyvinyl alcohol was dissolved in about 10 mL of dimethylsulfoxide to obtain a mixture, and stirred in a magnetic stirrer at about 90ºC to obtain a solution. The lignin was added to the obtained solution at about 60ºC, and stirred overnight in a magnetic stirrer, to obtain a homogenised solution.
Ratio of said lignin to said polyvinyl alcohol was about 70:30. For about 10 mL of the dimethylsulfoxide, weights of the lignin and the polyvinyl alcohol were about 2.1 g and about 0.9 g, respectively. The homogenised solution was casted in plates and solidified at about 20ºC for about 4 hours. The casted plates were dried at about 60ºC to obtain the membrane. The dried membrane was peeled and stored for further analyses. As shown in the below table, different membranes were fabricated by adding different concentrations of the lignin and the PVA,
Compositional Range
(Lignin: PVA) Results
10:90 Membrane disintegrated within 2 hours
20:80 Membrane disintegrated within 2 hours
30:70 Membrane disintegrated within 2 hours
40:60 No disintegration till 10 days
50:50 No disintegration till 10 days
60:40 No disintegration till 10 days
70:30 No disintegration till 10 days
80:20 No disintegration till 10 days
90:10 No disintegration till 10 days
As illustrated, in Figure 1A, dark brown and glossy membranes were obtained. Though all the above membranes were characterised and tested, only the results for the 70:30 membrane are provided below, as the 70:30 membrane yielded the best results.
Membrane Characterisations
Scanning Electron Microscope and Contact Angle Analyses
As illustrated, in Figure 1B, effective crosslinking and fine dispersion of the lignin in the PVA during homogenisation was obtained.
As illustrated, in Figure 1C, the fabricated membrane was determined to be hydrophilic and the contact angle was found to be about 53.52º.
X-ray Diffraction Analyses
As illustrated, in Figure 2A, characteristic peaks were observed in the region between about 25º to about 34º, confirming the fabricated membrane to be semicrystalline and porous, thereby supporting adsorption.
Tensile Strength Analyses
As illustrated, in Figure 2B, the fabricated membrane exhibited a tensile strength of about 50.4 MPa and a break elongation of about 42.83%, indicating good mechanical stability.
Thermogravimetric and Differential Scanning Calorimetric Analyses
As illustrated, in Figure 3, the fabricated membrane was determined to be effectively thermally stable.
As illustrated, in Figure 4, the glass transition temperature was found to be about 70.4ºC.
Adsorption, Desorption, and Reusability Analyses
Adsorption analyses were conducted to evaluate effectiveness of the fabricated lignin membrane in removing chemical dyes and heavy metals.
Desorption tests were conducted to ensure that the fabricated membrane can be effectively reused for multiple cycles, enhancing its efficiency and practicality.
The chemical dyes analysed were: methylene blue, congo red, crystal violet, and brilliant green. The heavy metals analysed were chromium and cobalt.
Methylene Blue
As illustrated, in Figure 5A and Figure 5B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 438.1 ± 76.4 (mg/g), with the adsorption process fitting better to a linear, compared to a non-linear Langmuir isotherm.
As illustrated, in Figure 6A and as shown in the below table, the fabricated membrane exhibited a heterogeneous surface with active adsorption sites, indicated by an N value of about 0.373, showing effective adsorption even at low dye concentrations, demonstrating a strong affinity for targeted adsorbates.
As illustrated, in Figure 6B and as shown in the below table, a strong dye affinity was indicated by the AT value, highlighting effective adsorption even at low dye concentrations.
As illustrated, in Figure 7A and as shown in the below table, the equilibrium adsorption time was found to be about 100 minutes. As illustrated, in Figure 7B and as shown in the below table, intraparticle diffusion analyses showed a certain boundary layer influencing the rate of the adsorption process.
As illustrated, in Figure 8A, Figure 8B, Figure 8C, Figure 8D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature, and the adsorption process was found to be endothermic.
As illustrated, in Figure 9B and as shown in the below table, maximum adsorption, achieving about 85% dye removal, was observed with about 0.1 g of the adsorbent. As illustrated, in Figure 9A and as show in the below table, maximum adsorption, achieving about 85% dye removal, was observed at a pH of about 2.
As illustrated, in Figure 10A, Figure 10B, and as shown in the below table, maximum desorption concentration was observed to be about 800 mg/L (Figure 10A), and high removal efficiency occurred in the 5th cycle during the reusability tests (Figure 10B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 438.1 ± 76.4 (mg/g) K= 0.00049 R2 = 0.955
Non-Linear Langmuir Qmax= 80.639 (mg/g) K= 0.00337 R2 = 0.98
Freundlich N = 0.373 Kf = 2.930 R2 = 0.972
Temkin AT = 14.68 BT = 0.058 R2 = 0.95
Adsorption Kinetics
Pseudo First-order Model Qe,cal=228.7 (mg/g) K= 0.00175 R2 = 0.95
Intraparticle Diffusion Model Kid = 2.20 C= 10.74 R2 = 0.93
Temperature Studies
Langmuir Model at 25ºC Qmax= 500 (mg/g) K= 0.00056 R2 = 0.971
Langmuir Model at 35ºC Qmax= 769.2 (mg/g) K = 0.00063 R2 = 0.96
Langmuir Model at 45ºC Qmax= 416.6 (mg/g) K= 0.0038 R2 = 0.91
Thermodynamic Parameters Hº = 1,02,723 Sº = 353.51
Thermodynamic Parameters Gº @ 25 = - 2,622.40 Gº @ 35 = - 6,095.58 Gº @ 45 = -9,692.28
pH Studies
% Removal with pH Maximum adsorption at pH 2 with 85 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.1 g adsorbent with 85 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 800 mg/L with 85 % removal
Reusability Studies
Number of Cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 3 with % removal of 82.23
Cycle at which high desorption efficiency is achieved At cycle 2 with % removal of 64.57
Cycle at which high removal efficiency obtained At cycle 5 with % removal of 95.7
Congo Red
As illustrated, in Figure 11A and Figure 11B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 126.32 ± 12.9 (mg/g), with the adsorption process fitting better to a linear, compared to a non- linear Langmuir isotherm.
As illustrated, in Figure 12A and as shown in the below table, the fabricated membrane exhibited a heterogeneous surface with increased active adsorption sites, indicated by an N value of about 1.075, showing effective adsorption for targeted adsorbates.
As illustrated, in Figure 12B and as shown in the below table, a strong dye affinity was indicated by the BT value, with the process being exothermic, exhibiting monolayer adsorption.
As illustrated, in Figure 13A and as shown in the below table, the equilibrium adsorption time was found to be about 90 minutes. As illustrated, in Figure 13B and as shown in the table below, intraparticle diffusion analyses showed presence of mild boundary layer effects that influence the rate of the adsorption process.
As illustrated, in Figure 14A, Figure 14B, Figure 14C, Figure 14D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature and when the temperature was increased to about 35ºC, the adsorption capacity has increased to Qmax= 526.3 (mg/g), and the adsorption process is found to be endothermic.
As illustrated, in Figure 15B and as shown in the below table, maximum adsorption, achieving about 99.4% dye removal, was observed with about 0.1 g of adsorbent. As illustrated, in Figure 15A and as shown in the below table, maximum adsorption, achieving about 99.4% dye removal, was observed at a pH of about 7.
As illustrated, in Figure 16A, Figure 16B, and as shown in the below table, maximum desorption concentration at about 600 mg/L (Figure 16A), and high removal efficiency occurred in the 3rd cycle during the reusability tests (Figure 16B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 126.32 ± 12.9 (mg/g) K= 0.0026 R2 = 0.975
Non-Linear Langmuir Qmax= 6.57 (mg/g) K= 0.093 R2 = 0.91
Freundlich N = 1.075 Kf = 0.065 R2 = 0.91
Temkin AT = 0.01 BT = 13.60 R2 = 0.96
Adsorption Kinetics
Pseudo First-order Model Qe,cal=122.6 (mg/g) K= 0.0105 R2 = 0.97
Intraparticle Diffusion Model Kid = 1.829 C= -1.654 R2 = 0.976
Temperature Studies
Langmuir Model at 25ºC Qmax= 434.7 (mg/g) K= 0.00022 R2 = 0.95
Langmuir Model at 35ºC Qmax= 526.3 (mg/g) K = 0.00093 R2 = 0.91
Langmuir Model at 45ºC Qmax= 285.7 (mg/g) K= 0.0034 R2 = 0.98
Thermodynamic Parameters Hº = 71483.77 Sº = 218.66
Thermodynamic Parameters Gº @ 25 = 6323.09 Gº @ 35 = 5229.79 Gº @ 45 = 1949.89
pH Studies
% Removal with pH Maximum adsorption at pH 7 with 49.42 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.1 g adsorbent with 99.4 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 600 mg/L with 98.9 % removal
Reusability Studies
Number of Cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 2 with % removal of 99.69
Cycle at which high desorption efficiency is achieved At cycle 3 with % removal of 80.87
Cycle at which high removal efficiency obtained At cycle 3 with % removal of 75.6
Crystal Violet
As illustrated, in Figure 17A and Figure 17B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 276.12 ± 84.9 (mg/g), with the adsorption process fitting better to a linear, compared to a non- linear Langmuir isotherm.
As illustrated, in Figure 18A and as shown in the below table, the fabricated membrane exhibited a heterogeneous surface with uniform adsorption sites, indicated by an N value of about 1.136, showing moderate adsorption for targeted adsorbates.
As illustrated, in Figure 18B and as shown in the below table, the values of AT and BT indicated weak binding with the adsorbent, showing gradual decrease in the heat of adsorption.
As illustrated, in Figure 19A and as shown in the below table, the equilibrium adsorption time was found to be about 90 minutes. As illustrated, in Figure 19B and as shown in the table below, intraparticle diffusion analyses showed faster diffusion and thick boundary layer effects, indicating that the adsorption was dependent on the surface interactions.
As illustrated, in Figure 20A, Figure 20B, Figure 20C, Figure 20D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature and the adsorption process is found to be endothermic.
As illustrated, in Figure 21B and as shown in the below table, maximum adsorption, achieving about 67.88% dye removal, was observed with about 0.2 g of adsorbent. As illustrated, in Figure 21A and as shown in the below table, maximum adsorption, achieving about 67.88% dye removal, was observed at a pH of about 8.
As illustrated, in Figure 22A, Figure 22B, and as shown in the below table, maximum desorption concentration at about 600 mg/L (Figure 22A), and high removal efficiency occurred in the 5th cycle during the reusability tests (Figure 22B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 276.12 ± 84.9 (mg/g) K= 0.00126 R2 = 0.96
Non-Linear Langmuir Qmax= 146.26 (mg/g) K= 0.00034 R2 = 0.92
Freundlich N = 1.136 Kf = 0.390 R2 = 0.96
Temkin AT = 0.034 BT = 23.95 R2 = 0.93
Adsorption Kinetics
Pseudo First-order Model Qe,cal=212.72 (mg/g) K= 0.0186 R2 = 0.98
Intraparticle Diffusion Model Kid = 1.22 C= 5.96 R2 = 0.992
Temperature Studies
Langmuir Model at 25ºC Qmax= 200 (mg/g) K= 0.0030 R2 = 0.90
Langmuir Model at 35ºC Qmax= 144.9 (mg/g) K = 0.0068 R2 = 0.96
Langmuir Model at 45ºC Qmax= 666.6 (mg/g) K= 0.001 R2 = 0.981
Thermodynamic Parameters Hº = 33928.5 Sº = 81.72
Thermodynamic Parameters Gº @ 25 = 9576.03 Gº @ 35 = 8758.83 Gº @ 45 = 7941.63
pH Studies
% Removal with pH Maximum adsorption at pH 8 with 67.88 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.2 g adsorbent with 82.84 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 600 mg/L with 90.47 % removal
Reusability Studies
Number of Cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 3 with % removal of 87.55
Cycle at which high desorption efficiency is achieved At cycle 5 with % removal of 79.79
Cycle at which high removal efficiency obtained At cycle 5 with % removal of 88.6
Brilliant Green
As illustrated, in Figure 23A and Figure 23B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 568.91 ± 19.6 (mg/g), with the adsorption process fitting better to a linear, compared to a non- linear Langmuir isotherm.
As illustrated, in Figure 24A and as shown in the below table, the fabricated membrane exhibited a heterogeneous surface with an N value of about 2.17 and a Kf value of about 1.217, showing moderate adsorption for targeted adsorbates.
As illustrated, in Figure 24B and as shown in the below table, the values of AT = 0.101 and BT = 4.714, indicated weak binding interactions and low energy involved in the adsorption process, leading to relatively low adsorption efficiency.
As illustrated, in Figure 25A, and as shown in the below table, the equilibrium adsorption time was found to be about 60 minutes. As illustrated, in Figure 25B, and as shown in the below table, intraparticle diffusion analyses showed a certain boundary layer, influencing the rate of the adsorption process.
As illustrated, in Figure 26A, Figure 26B, Figure 26C, Figure 26D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature and the adsorption process is found to be endothermic.
As illustrated, in Figure 27B and as shown in the below table, maximum adsorption, achieving about 91.25% dye removal, was observed with about 0.2 g of adsorbent. As illustrated, in Figure 27A and as shown in the below table, maximum adsorption, achieving about 91.25% dye removal, was observed, at a pH of about 10.
As illustrated, in Figure 28A, Figure 28B, and as shown in the below table, maximum desorption concentration at about 1000 mg/L (Figure 28A), and high removal efficiency occurred in the 5th cycle during the reusability tests (Figure 28B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 568.91 ± 19.6 (mg/g) K= 0.00017 R2 = 0.95
Non-Linear Langmuir Qmax= 20.29 (mg/g) K= 0.0116 R2 = 0.906
Freundlich N = 2.17 Kf = 1.217 R2 = 0.95
Temkin AT = 0.101 BT = 4.714 R2 = 0.92
Adsorption Kinetics
Pseudo First-order Model Qe,cal=357.6 (mg/g) K= 0.005 R2 = 0.99
Intraparticle Diffusion Model Kid = 0.141 C= 8.61 R2 = 0.977
Temperature Studies
Langmuir Model at 25ºC Qmax= 833.33 (mg/g) K= 0.0021 R2 = 0.98
Langmuir Model at 35ºC Qmax= 980.39 (mg/g) K = 0.0013 R2 = 0.90
Langmuir Model at 45ºC Qmax= 142.85 (mg/g) K= 0.021 R2 = 0.969
Thermodynamic Parameters Hº = 4090.48 Sº = 3.965
Thermodynamic Parameters Gº @ 25 = 2908.91 Gº @ 35 =2869.26 Gº @ 45 =2829.61
pH Studies
% Removal with pH Maximum adsorption at pH 10 with 91.25 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.2 g adsorbent with 92.02 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 1000 mg/L with 90.14 % removal
Reusability Studies
Number of Cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 1 with % removal of 77.16
Cycle at which high desorption efficiency is achieved At cycle 2 with % removal of 98.50
Cycle at which high removal efficiency obtained At cycle 5 with % removal of 25.6
Chromium
As illustrated, in Figure 29A and Figure 29B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 447 ± 16.2 (mg/g), with the adsorption process fitting better to a linear, compared to a non- linear Langmuir isotherm.
As illustrated, in Figure 30A and as shown in the below table, the fabricated membrane exhibited a moderate heterogeneous surface with active adsorption sites, indicated by an N value of about 1.29, showing effective adsorption even at very low concentrations for targeted adsorbates.
As illustrated, in Figure 30B and as shown in the below table, a strong dye affinity was indicated by the AT value, showing effective adsorption even at low concentrations.
As illustrated, in Figure 31A and as shown in the below table, the equilibrium adsorption time was found to be about 80 minutes. As illustrated, in Figure 31B and as shown in the below table, intraparticle diffusion analyses showed certain boundary layer that influence the rate of the adsorption process.
As illustrated, in Figure 32A, Figure 32B, Figure 32C, Figure 32D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature and the adsorption process is found to be endothermic.
As illustrated, in Figure 33B and as shown in the below table, maximum adsorption, achieving about 89.36% dye removal, was observed with about 0.05 g of adsorbent. As illustrated, in Figure 33A and as shown in the below table, maximum adsorption, achieving about 89.36% dye removal, was observed at a pH of about 10.
As illustrated, in Figure 34A, Figure 34B, and as shown in the below table, maximum desorption concentration at about 800 mg/L (Figure 34A), and high removal efficiency occurred in the 5th cycle during the reusability tests (Figure 34B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 447.17 ± 16.2 (mg/g) K= 0.0014 R2 = 0.951
Non-Linear Langmuir Qmax= 144.7 (mg/g) K= 0.00043 R2 = 0.96
Freundlich N = 1.29 Kf = 0.206 R2 = 0.97
Temkin AT = 0.010 BT = 17.66 R2 = 0.95
Adsorption Kinetics
Pseudo First-order Model Qe,cal=147.82(mg/g) K= 0.016 R2 = 0.91
Intraparticle Diffusion Model Kid = 2.53 C= -2.24 R2 = 0.91
Temperature Studies
Langmuir Model at 25ºC Qmax= 166.67 (mg/g) K= 0.0006 R2 = 0.92
Langmuir Model at 35ºC Qmax= 161.29 (mg/g) K = 0.00035 R2 = 0.910
Langmuir Model at 45ºC Qmax= 256.41 (mg/g) K= 0.00068 R2 = 0.926
Thermodynamic Parameters Hº = 13284.77 Sº = 30.055
Thermodynamic Parameters Gº @ 25 = -61778.65 Gº @ 35 =-63677.42 Gº @ 45 =-66176.20
pH Studies
% Removal with pH Maximum adsorption at pH 10 with 11.22 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.05 g adsorbent with 46.93 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 800 mg/L with 93.68 % removal
Reusability Studies
Number of cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 1 with % removal of 97.69
Cycle at which high desorption efficiency is achieved At cycle 5 with % removal of 94.90
Cycle at which high removal efficiency obtained At cycle 5 with % removal of 89.36
Cobalt
As illustrated, in Figure 35A and Figure 35B, and as shown in the below table, the fabricated membrane exhibited a maximum adsorption capacity of Qmax= 691.08 ± 38 (mg/g), with the adsorption process fitting better to a linear, compared to a non- linear Langmuir isotherm.
As illustrated, in Figure 36A and as shown in the below table, the fabricated membrane exhibited a heterogeneous surface with active adsorption sites, indicated by an N value of about 2.74, showing effective adsorption even at very low concentrations for targeted adsorbates.
As illustrated, in Figure 36B and as shown in the below table, the AT value showed strong affinity towards the adsorbents, showing effective adsorption even at low concentrations of metal.
As illustrated, in Figure 37A and as shown in the below table, the equilibrium adsorption time was found to be about 100 minutes. As illustrated, in Figure 37B and as shown in the below table, intraparticle diffusion analyses showed certain boundary layer that influence the rate of the adsorption process.
As illustrated, in Figure 38A, Figure 38B, Figure 38C, Figure 38D, and as shown in the below table, the process was found to be spontaneous, the spontaneity of the reaction increased with an increase in the temperature and the adsorption process is found to be endothermic.
As illustrated, in Figure 39B and as shown in the below table, maximum adsorption, achieving about 97.75%, dye removal, was observed with about 0.2 g of adsorbent. As illustrated, in Figure 39A and as shown in the below table, maximum adsorption, achieving about 97.75%, dye removal, was observed at a pH of about 10.
As illustrated, in Figure 40A, Figure 40B, and as shown in the below table, maximum desorption concentration at about 800 mg/L (Figure 40A), and high removal efficiency occurred in the 2nd cycle during the reusability tests (Figure 40B), respectively.
Analyses Results
Adsorption Isotherms
Linear Langmuir Qmax= 691.08 ± 38.9 (mg/g) K= 0.0034 R2 = 0.953
Non-Linear Langmuir Qmax= 21.43 (mg/g) K= 0.0048 R2 = 0.92
Freundlich N = 2.439 Kf = 1.015 R2 = 0.93
Temkin AT = 0.048 BT = 4.44 R2 = 0.95
Adsorption Kinetics
Pseudo First-order Model Qe,cal=287.89(mg/g) K= 0.0103 R2 = 0.98
Intraparticle Diffusion Model Kid = 3.71 C= -15.62 R2 = 0.92
Temperature Studies
Langmuir Model at 25ºC Qmax= 166.67 (mg/g) K= 0.0076 R2 = 0.96
Langmuir Model at 35ºC Qmax= 136.98 (mg/g) K = 0.0015 R2 = 0.98
Langmuir Model at 45ºC Qmax= 204.08 (mg/g) K= 0.0012 R2 = 0.94
Thermodynamic Parameters Hº = 78269.40 Sº = 232.958
Thermodynamic Parameters Gº @ 25 = 8847.8 Gº @ 35 = 6517.93 Gº @ 45 = 4188.75
pH Studies
% Removal with pH Maximum adsorption at pH 10 with 97.75 % removal
Adsorbent Dosage Studies
% Removal with mass of the adsorbent Maximum adsorption at 0.2 g adsorbent with 22.68 % removal
Desorption Studies
% Desorbed with concentration Maximum desorption concentration at 800 mg/L with 97.17% removal
Reusability Studies
Number of Cycles 5
Cycle at which high adsorption efficiency is achieved At cycle 3 with % removal of 96.61
Cycle at which high desorption efficiency is achieved At cycle 2 with % removal of 66.9
Cycle at which high removal efficiency obtained At cycle 2 with % removal of 95.7
From the above results, it was observed that the fabricated membrane showed effective removal of chemical dyes (methylene blue, congo red, crystal violet, and brilliant green) and heavy metals (chromium and cobalt). The fabricated membrane with compositional range of about 70:30 (Lignin: PVA) showed maximum adsorptive capacity of dyes and heavy metals.
The disclosed method of fabrication offers at least the following advantages and effects: is cost-effective; is eco-friendly (is plant-based); reduced process times; improved efficiency; is efficient in removing a broad spectrum of chemical dyes and heavy metals; and/or is reusable, with a high reusability efficiency.
The maximum adsorption capacities reported in the existing art are Qmax =167 mg/g for brilliant green, Qmax = 382.5 mg/g for chromium, and Qmax = 160 mg/g for cobalt, whereas, the maximum adsorption capacities reported in the present disclosure are Qmax = 568.91± 19.6 mg/g for brilliant green, Qmax = 447.17 ± 16.2 (mg/g) for chromium, and Qmax = 691.08 ± 38.9 (mg/g) for cobalt. For the other dyes and heavy metals, the results that were obtained in the present disclosure are comparable with previously reported results.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements, without deviating from the spirit and the scope of the disclosure, may be made, by a person skilled in the art. Such modifications, additions, alterations, and improvements, should be construed as being within the scope of this disclosure. , Claims:1. An ecofriendly method of fabricating a lignin membrane for waste water treatment, said method comprising steps of:
soaking a powder of Sterculia foetida shells in a sodium hydroxide and sodium sulphide mixture to obtain lignin; with: ratio of said sodium hydroxide to said sodium sulphide being 4.1:1;
dissolving polyvinyl alcohol in dimethylsulfoxide to obtain a mixture;
stirring the mixture at 90ºC to obtain a solution;
adding the lignin to the solution, followed by stirring overnight, at 60ºC to obtain a homogenised solution; with: ratio of said lignin to said polyvinyl alcohol being 70:30; and
casting and solidifying the homogenised solution, for 4 hours at 20ºC, followed by drying at 60ºC.
2. The ecofriendly method of fabricating a lignin membrane for waste water treatment, as claimed in claim 1, wherein:
1 g of said powder of Sterculia foetida shells is soaked in 0.284 g of said sodium hydroxide and 0.0692 g of said sodium sulphide.
3. The ecofriendly method of fabricating a lignin membrane for waste water treatment, as claimed in claim 1, wherein: size of said powder of Sterculia foetida shells is 1 mm.
4. The ecofriendly method of fabricating a lignin membrane for waste water treatment, as claimed in claim 1, wherein: 0.9 g of the polyvinyl alcohol is dissolved in 10 mL of the dimethylsulfoxide.

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