Treatment of methylene blue containing wastewater by a cost-effective micro-scale biochar/polysulfone mixed matrix hollow fiber membrane: Performance and mechanism studies

Adsorptive membrane separation for eco-friendly decontamination of chlorpyrifos via biochar-impregnated cellulose acetate mixed matrix membrane

In this work, the phase inversion approach is used to synthesize a blended mixed matrix membrane from cellulose acetate polymer and sugarcane bagasse biochar. The experiments were carried out to estimate the extent of chlorpyrifos (CPS) pesticide removal. The results showed that the removal rate was more than 99% in making the filtered water suitable enough for domestic use. The physical and functional characteristics of the membranes, such as permeability, and contact angle were identified. The changes in the membrane characteristics were observed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction both before and after the experimental trials. Experiments were conducted to assess not only the rejection characteristics of CPS, as a function feed concentration, but also the effect co-ions on the rejection used to analyze the composition both before and after filtration. The effects of initial CPS concentration, biochar loading, and co-ions on the membrane were investigated. The membranes showed contact angles between 70° and 97° and a permeability between 0.25 × 1010 m Pa-1 s-1 and 0.31 × 1010 m Pa-1 s-1. The effective removal of CPS from the contaminated aqueous stream was attributed to a combination of adsorptive uptake and membrane-based separation. CPS was found to get adsorbed onto the membrane matrix through an intraparticle diffusion mechanism along with an irreversible monolayer adsorption. The membrane-solute adsorptive interaction was represented by Langmuir isotherm and intraparticle diffusion models with a maximum adsorption capacity of 192.3 mg g-1. The findings indicated the efficacy of biochar-cellulose acetate mixed matrix membrane for sustainable and eco-friendly treatment of chlorpyrifos contaminated water.

The bio-adsorption competence of tailor made lemon grass adsorbents on oils: An in-vitro approach

The oil contamination in aquatic system is considered as most serious environmental issues and identifying a suitable ecofriendly solution for this oil pollution management is critical. Hence, this research was designed to evaluate the oils (petrol, diesel, engine oil, and crude oil) adsorptive features through raw lemon grass adsorbent, physically/chemically treated adsorbents. Initially, such raw and treated adsorbents were characterized by Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS) analysis. These characterization techniques revealed that the lemon grass adsorbent had considerable level of pollutant adsorption potentials owing to porous morphological structure, active functional groups and pollutants interaction with chemical elements. The physically treated adsorbent exhibited better adsorption characteristics than others. Accordingly, the petrol adsorption potential of raw adsorbent, physically treated and chemically treated ones was discovered as their weight incremented up to 2.0, 3.0, and 1.5 times their initial weight, respectively. Similarly, the weight of raw form, physically and chemically treated ones on diesel had increased significantly, up to 2.5 times, 4.0 times, and 2.0 times, respectively. It was evaluated that the weight of these tested adsorbents on engine oil incremented by 3.5, 5.0, and 3.0 times their initial weight, while on crude oil these incremented by 4.0, 6.0, and 4.0 times their initial weight respectively. When the media are compared, it's indeed evident about absorption which is preferred as follows: Crude oil, engine oil, diesel, and petrol. The physically treated lemon grass adsorbent showed maximum adsorption and retention potential than others. The kinetic study reveals that the pseudo second order kinetics is the best fit for the adsorption of oil with R² value of 0.99.

Chemically activated carbon preparation from natural rubber biosludge for the study of characterization, kinetics and isotherms, thermodynamics, reusability during Cr(VI) and methylene blue adsorption

Alkaline leachate, dust generation, and foul smell during the stacking process of natural rubber biosludge (NRBS) can pollute surrounding water, soil, and air. In this study, natural rubber chemically activated carbon (NRCAC) has been synthesized for the first time from NRBS by pyrolysis using ZnCl₂ at 700 °C for adsorptive removal of Cr(VI) and methylene blue (MB) from aqueous solutions. Both NRBS and NRCAC were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET), and thermogravimetric analyzer (TGA). FTIR and SEM-EDS suggested significant functional and morphological transformations in NRCAC. Experimental investigations of different process parameters, such as pH, concentration, contact time, salt concentration, etc., were conducted to study their influences on adsorption. Adsorption and desorption kinetics followed a pseudo-second-order model, while adsorption equilibrium followed Liu isotherm. Maximum uptake calculated from the Liu model was 81.28 and 211.90 mg/g for Cr(VI) and MB, respectively. Thermodynamic analysis established spontaneous and endothermic adsorption. Up to five adsorption/desorption cycles were conducted using eluents such as 1 M NaOH and water for Cr(VI) and MB, respectively. Electrostatic attraction and ion-exchange favored Cr(VI)/MB adsorption, while hydrogen bonding and π-π stacking were significant in MB uptake. Overall findings suggest that NRBS (a renewable agro-industrial, abundant, and freely available) could be employed to synthesize biochar for adsorptive removal of wastewater containing Cr(VI)/MB.

Natural and recycled materials for sustainable membrane modification: Recent trends and prospects

Despite water being critical for human survival, its uneven distribution, and exposure to countless sources of pollution make water shortages increasingly urgent. Membrane technology offers an efficient solution for alleviating the water shortage impact. The selectivity and permeability of membranes can be improved by incorporating additives of different nature and size scales. However, with the vast debate about the environmental and economic feasibility of the common nanoscale materials in water treatment applications, we can infer that there is a long way before the first industrial nanocomposite membrane is commercialized. This stumbling block has motivated the scientific community to search for alternative modification routes and/or materials with sustainable features. Herein, we present a pragmatic review merging the concept of sustainability, nanotechnology, and membrane technology through the application of natural additives (e.g., Clays, Arabic Gum, zeolite, lignin, Aquaporin), recycled additives (e.g., Biochar, fly ash), and recycled waste (e.g., Polyethylene Terephthalate, recycled polystyrene) for polymeric membrane synthesis and modification. Imparted features on polymeric membranes, induced by the presence of sustainable natural and waste-based materials, are scrutinized. In addition, the strategies harnessed to eliminate the hurdles associated with the application of these nano and micro size additives for composite membranes modification are elaborated. The expanding research efforts devoted recently to membrane sustainability and the prospects for these materials are discussed. The findings of the investigations reported in this work indicate that the application of natural and waste-based additives for composite membrane fabrication/modification is a nascent research area that deserves the attention of both research and industry.

Powdered activated carbon-catalyzed chlorine oxidation of bisphenol-A and methylene blue: Identification of the free radical and effect of the carbon surface functional group

The effect of powdered activated carbon (PAC) on chlorine oxidation is not well understood, therefore this study was designed to further investigate the chlorine oxidation mechanism with the presence of PAC. The oxidation processes of two model organic pollutants (bisphenol-A and methylene blue) with chlorine were compared in the absence and presence of PAC. The results showed a significant increase in reaction rates with the addition of PAC. Electron spin resonance indicated that the PAC catalyzed the oxidation of chlorine to generate more Cl and O₂^-. Additionally, the analysis of the surface characteristics of thermally modified PACs under N₂ and their corresponding reaction rates revealed that there existed a significant correlation between the CO groups and the catalytic effect. PAC exhibited a much lower reaction rate under H₂ modification, which indicated that the π electrons of the basal plane might be involved in the catalysis. Density functional theory calculations confirmed that the various oxygen groups on PAC reduced the activation barrier for HOCl dissociation, particularly the carboxyl group. This investigation provides a better understanding of the interactions between chlorine and activated carbon materials, which could be useful for selecting suitable water treatment agents.

Preparation of hyper-cross-linked hydroxylated polystyrene for adsorptive removal of methylene blue

A series of hydroxylated polystyrene (PS-OH) resins were prepared from macroporous poly(styrene-co-divinylbenzene) by nitration, reductive amination, diazotation and hydrolysis in sequence, and then a series of hyper-cross-linked hydroxylated polystyrene (HCPS-OH) resins were successfully prepared from the PS-OH resins by the Friedel–Crafts post-cross-linking using dichloromethane as an external cross-linker. Benefiting from the synthetic protocol, the HCPS-OH resins showed better adsorption performance for methylene blue in aqueous solution as compared with the corresponding PS-OH resins. HCPS-OH-4, one of the fabricated HCPS-OH resins which had the hydroxyl content of 5.0 mmol g⁻¹ and BET specific surface area of 69.0 m² g⁻¹, showed the highest adsorption capacity and selectivity for methylene blue. Higher temperature, higher pH, and higher ionic strength were beneficial to adsorption of methylene blue from aqueous solution. HCPS-OH-4 could be regenerated by treatment with 1.0 M HCl methanol solution and deionized water sequentially. Moreover, HCPS-OH-4 retained good adsorption performance for methylene blue even after 5 cycles of adsorption and regeneration, which implied that it was a good candidate for adsorptive removal of methylene blue dye in waste water.

This study presents the preparation of hyper-cross-linked hydroxylated polystyrene (HCPS-OH) resins using dichloromethane as an external cross-linker for the adsorption of methylene blue.

Preparation of a PES/PFSA-g-MWCNT ultrafiltration membrane with improved permeation and antifouling properties

In this study, perfluorosulfonic acid (PFSA) was firstly grafted on multi-walled carbon nanotubes (MWCNTs) to obtain PFSA-g-MWCNT nanocomposites.

Design and Synthesis of a Dual-Purpose Superadsorbent Containing a High Density of Chelating Motifs for the Fast Mitigation of Methylene Blue and Pb(II)

Maleic acid underwent alternate copolymerization with diallylaminomethylphosphonic acid·HCl [(CH2=CHCH2)2NH+CH2PO3H2 Cl-] and a cross-linker to give a new pH-responsive resin. Methylene blue (MB) removal from its 3000 ppm solution by the resin at pH 7 followed second-order kinetics with an E a of 34.8 kJ mol-1. MB removal was achieved very fast (10 min), attaining over 98.5% at 328 K. The q e obtained using MB concentrations in the range 100-8000 ppm fitted the Langmuir nonlinear isotherm model to give ΔG o, ΔH o, and ΔS o values of ≈ -21 kJ, 36.5 kJ mol-1, and 185 J mol-1 K-1, respectively. The resin is a superadsorbent with a q max value of 2445 mg g-1. The adsorbent also removed 97% Pb(II) within 5 min from its 10 000 ppb solution. The resin reduced the Pb(II) concentration from 200 to 3.8 ppb. The resin also demonstrated its ability to remove contaminants from industrial wastewater, reducing priority metal contaminants to ppb and sub-ppb levels. The resin can be recycled with stable efficiency. The outstanding performance places the resin in a top position in a list of recently reported sorbents.

Utilization of nano-olive stones in environmental remediation of methylene blue from water

BACKGROUND

The use of agricultural waste as a low-cost adsorbent for the removal of hazardous methylene blue (MB) from aqueous solution was investigated. In this research, the potentiality of using black nano olive stones (black NOS) and green nano olive stones (green NOS) for MB adsorption was conducted.

METHODS

Various remediation parameters such as initial MB concentration, pH, and temperature were investigated. Thermodynamic study was carried out to determine the homogeneity of the adsorbent and spontaneity of the adsorption process. Different physical and chemical characterizations were studied using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET) surface area, pore radius and pore volume.

RESULTS

It was found that NOS exhibits an acidic nature, however the highest MB removal efficiency was recorded at pH 10; reaching up to 71%. The negative value of the heat of the adsorption process (∆H ° ) indicated the reaction followed an exothermic pathway while the negative value of Gibbs adsorption (∆G ° ) further suggested its spontaneous nature. The results indicated that the Freundlich model described well the adsorption process with 99.5% correlation coefficient for green NOS. FTIR was used to analyze functional groups on the adsorbents' surfaces that could play vital roles in the remediation process. SEM analysis revealed that the adsorbents comprised of abundant spherical deep cavities and porous nature.

CONCLUSION

The result obtained successfully demonstrated the potential of using black and green NOS as suitable adsorbents for the removal of MB from water.

Removal of methylene blue from aqueous solutions by biochar prepared from the pyrolysis of mixed municipal discarded material

This paper investigates the adsorption of organic compounds in aqueous solution to biochar adsorbent, using methylene blue as an indicator for adsorption. Biochar was produced by the pyrolysis of mixed municipal discarded material in an innovative heat pipe reactor, the pyrolysis temperature was held at 300°C for 12 h. Biochar produced under these conditions was found to have oxygen containing functional groups that are beneficial to the adsorption of methylene blue as well as graphitic structures suggesting potential sites for π-π interactions with methylene blue. Methylene Blue followed the pseudo second order kinetic model with higher R² values than both the pseudo first order kinetic and intraparticle diffusion models. The adsorption also closely fit the Langmuir isotherm rather than the Freundlich model, suggesting monolayer adsorption rather than multilayer adsorption. Maximum adsorption capacity was observed at 7.2 mg/g for initial concentration of 100 mg/l Methylene blue in aqueous solution. The amount of Methylene blue adsorbed increased with increasing initial concentration as expected. The adsorption mechanisms are likely π-π interactions between methylene blue and the graphitic structures in the biochar which are shown to be present in Raman spectroscopy, as well as electrostatic attraction and ionic bonding between negatively charged surface sites on the char and the positive charge on the dissolved methylene blue molecules. The results show that biochar obtained from mixed waste could be employed as a low-cost and effective tool in water treatment for the removal of basic dyes and potentially other organic impurities.

A Review of Non-Soil Biochar Applications

Biochar is the solid residue that is recovered after the thermal cracking of biomasses in an oxygen-free atmosphere. Biochar has been used for many years as a soil amendment and in general soil applications. Nonetheless, biochar is far more than a mere soil amendment. In this review, we report all the non-soil applications of biochar including environmental remediation, energy storage, composites, and catalyst production. We provide a general overview of the recent uses of biochar in material science, thus presenting this cheap and waste-derived material as a high value-added and carbonaceous source.

Fast removal of methylene blue and Hg(II) from aqueous solution using a novel super-adsorbent containing residues of glycine and maleic acid

The alternate cyclo-copolymerization of diallylammonioethanoate [(CH₂=CHCH₂)₂NCH₂CO₂^-] and maleic acid in the presence of a cross-linker afforded a novel pH-responsive resin (90% yield). The resin has turned out to be a super-adsorbent for methylene blue (MB) removal with a q_Max of 2101 mg g^-1. The adsorption of the dye followed pseudo second-order kinetics with an energy of activation (E_a) of 31.5 kJ mol^-1. The process showed an extraordinarily fast adsorption rate owing to faster film diffusion; the resin (250 mg) was able to trap 78 and 99.4% MB from its 3000 mg L^-1 solution (100 mL) within 3 and 30 min, respectively. Equilibrium constants from Langmuir nonlinear isotherm model in the range 288-328 K gave ΔG^o ΔH^o, and ΔS^o values of ≈ -25 kJ, -13 kJ and 39.5 J mol^-1 K^-1, respectively. Immobilization mechanism was discussed using FTIR, SEM, and Elovich kinetic model. The presence of the chelating glycine residues was exploited for the removal of Hg(II) ions; the q_Hg was determined to be 263 mg g^-1. The resin also removed MB and Hg(II) simultaneously from industrial wastewater with remarkable efficacy. The very impressive performance along with efficient recycling conferred the resin a top position among many sorbents.

Enhanced photocatalytic performance of magnetic multi-walled carbon nanotubes/cerium dioxide nanocomposite

An easily separated photocatalyst, magnetic multi-walled carbon nanotubes/cerium dioxide (MMWCNTs-CeO₂) nanocomposite, has been successfully prepared by hydrothermal synthesis and subsequent loading of magnetic nanoparticles. The synthesized nanocomposite was characterized by scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and vibrating sample magnetometer. The characterization results indicated the successful synthesis of MMWCNTs-CeO₂ nanocomposite. Photocatalytic degradation experiments were conducted to evaluate photocatalytic properties of MMWCNTs-CeO₂ by using methylene blue (MB) as a model pollutant. After a light irradiation of two hours, relatively high degradation efficiency (97.5%) of MB was achieved by using MMWCNTs-CeO₂ nanocomposite as photocatalyst in the presence of H₂O₂. The incorporation of magnetic nanoparticles could not only facilitate the separation of photocatalyst from the solution after treatment, but also enhance the photocatalytic degradation efficiency. The results of this study suggested that the synthesized MMWCNTs-CeO₂ nanocomposite showed an attractive prospect for application in the treatment of organic wastewater.

Chemical reduction of methylene blue in the presence of nanocatalysts: a critical review

Methylene blue (MB) (3,7-bis (dimethylamino)-phenothiazin-5-ium chloride) is a harmful pollutant and has been long been known for its detrimental effects on human health. Over the recent years, many strategies including reduction, oxidation, biological and photochemical degradation have been reported for converting this harmful dye into commercially useful products. Among the aforementioned strategies, the nanocatalytic reduction of MB into its reduced counterpart, i.e. leucomethylene blue, is considered more preferable because it has been reported to have numerous applications in various industrial fields in the academic literature. The reduction of MB is the kinetically unfavorable reaction. Henceforth, various nanocatalytic systems utilizing different kinds of stabilization mediums have reportedly been used for speeding up this particular reaction. This article attempts to not only describe the fundamental properties of the reduction reaction of MB but also present the classification of the recently reported nanocatalytic assemblies on the basis of the utilized supporting medium. Various techniques used for the characterization of nanocatalytic systems reported for the reduction of MB have been summarized in this review. The thermodynamics, kinetics and mechanistic studies of this nanocatalytic reaction have also been narrated here. This critical review has been written comprehensively to abridge the recent research progress in the assemblage of nanocatalytic systems used for the reduction of MB and to propose some new ideas for further development in this area.

Preparation of gemini surfactant/graphene oxide composites and their superior performance for Congo red adsorption

Gemini surfactant/GO composites (10-2-10/GO, 12-2-12/GO, and 14-2-14/GO) have been successfully prepared using three gemini surfactants with different tail chain lengths. The morphology and physicochemical properties of the as-synthesized composites were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gemini surfactant/GO composites were applied to the adsorption of Congo red dye, and from the experimental data, optimum adsorption conditions, adsorption kinetics, and isotherms were obtained. The removal process was favorable at acidic pH and reached equilibrium in ∼60 min. The results showed that the pseudo-second-order model and the Langmuir adsorption isotherm were a good fit for the adsorption of Congo red onto gemini surfactant/GO composites. Compared with other adsorbents reported in the literature, these composites showed superior Congo red adsorption capabilities, with absorption capacities as high as 2116, 2193, and 2325 mg g⁻¹ for 10-2-10/GO, 12-2-12/GO, and 14-2-14/GO, respectively. Moreover, the adsorption capacities were more than 1000 mg g⁻¹ even for the fifth cycle. The results of the present study substantiate that the gemini surfactant/GO composites are promising adsorbents for the removal of organic dyes in wastewater treatment.

Gemini surfactant/GO composites were prepared for the removal of Congo red dye, and show excellent adsorption capacities and reusabilities.