Influence of sodium dodecyl sulfate coating on adsorption of methylene blue by biochar from aqueous solution

Adsorption of common greywater pollutants and nutrients by various biochars as potential amendments for nature-based systems: Laboratory tests and molecular dynamics

Spruce wood and Typha (wetland plant) derived biochars pyrolyzed at 350 °C and 600 °C were tested for their sorption affinity for organic pollutants (diclofenac, methylparaben, benzotriazole and sodium 1-decanesulfonate) and nutrients (nitrate, ammonium, phosphate and boron) commonly found in greywater. Batch and column studies combined with molecular dynamics modelling determined the sorption capacity, kinetics, and described the underlying mechanisms. The spruce biochar (600 °C) exhibited the highest sorption capacity mainly for the tested organics. The dynamic test performed for spruce biochar (600 °C) showed that the magnitude of desorption was low, and the desorbed amount ranged between 3 and 11 %. Molecular dynamics modelling (a computational tool for elucidating molecular-level interactions) indicated that the increased sorption of nitrate and boron on spruce biochar (600 °C) could be attributed to hydrophobic interactions. The molecular dynamics shows that predominant adsorption of organic pollutants was governed by π-π stacking, with a minor role of hydrogen-bonding on the biochar surface. In summary, higher pyrolysis temperature biochar yielded greater adsorption capacity greywater borne contaminants and the reaction temperature (10-34 °C) and presence of anionic surfactant had a limited effect on the adsorption of organic pollutants, suggesting efficacious application of biochar in general for greywater treatment in nature-based systems.

From Waste to Resource: Valorization of Lignocellulosic Agri-Food Residues through Engineered Hydrochar and Biochar for Environmental and Clean Energy Applications-A Comprehensive Review

Agri-food residues or by-products have increased their contribution to the global tally of unsustainably generated waste. These residues, characterized by their inherent physicochemical properties and rich in lignocellulosic composition, are progressively being recognized as valuable products that align with the principles of zero waste and circular economy advocated for by different government entities. Consequently, they are utilized as raw materials in other industrial sectors, such as the notable case of environmental remediation. This review highlights the substantial potential of thermochemical valorized agri-food residues, transformed into biochar and hydrochar, as versatile adsorbents in wastewater treatment and as promising alternatives in various environmental and energy-related applications. These materials, with their enhanced properties achieved through tailored engineering techniques, offer competent solutions with cost-effective and satisfactory results in applications in various environmental contexts such as removing pollutants from wastewater or green energy generation. This sustainable approach not only addresses environmental concerns but also paves the way for a more eco-friendly and resource-efficient future, making it an exciting prospect for diverse applications.

Enhanced Adsorption of Tetracycline by Thermal Modification of Coconut Shell-Based Activated Carbon

Tetracycline (TC) is one of the most frequently detected antibiotics in various water matrices, posing adverse effects on aquatic ecosystems. In this study, coconut shell-based powdered activated carbon (PAC) was thermally modified under various temperatures to enhance TC adsorption. The PAC subjected to 800 °C (PAC800) showed the best TC adsorption. PAC and PAC800 were characterized using N₂ adsorption/desorption isotherm, X-ray photoelectron spectroscopy, Raman spectroscopy, XRD, Boehm titration, and zeta potential analyses. Increases in the specific surface area, C/O ratio, C=O, surface charge, basic groups, and the number of stacked graphene layers along with a decrease in structural defects were observed for PAC800 compared to PAC. The TC adsorption was significantly improved for PAC800 compared to that of PAC, which is attributable to the enhanced electrostatic attraction and π-π EDA interactions induced by the changes in the properties. The Freundlich isotherm was the best fit indicating the heterogeneous nature, and the Freundlich constant of PAC and PAC800 increased from 85.8 to 119.5 and 132.1 to 178.6 (mg/g)‧(L/mg)^1/n, respectively, when the temperature was increased from 296.15 to 318.15 K. The kinetics were well described by the pseudo-second-order adsorption model and the rate constant of PAC and PAC800 increased from 0.80 to 1.59 and from 0.72 to 1.29 × 10^-3 g/mg‧min, respectively, as the temperature was increased. The activation energy of PAC and PAC800 was 23.7 and 19.6 J/mol, respectively, while the adsorption enthalpy was 196.7 and 98.5 kJ/mol, respectively, indicating endothermic nature. However, it was suggested that TC adsorption onto PAC800 was more favorable and was more contributed to by physisorption than that onto PAC. These results strongly suggest that the properties, adsorption capacity, and adsorption mechanisms of carbonaceous adsorbents can be significantly changed by simple thermal treatment. More, the results provide valuable information about the design of carbonaceous adsorbents with better performance where the structures and functional groups, which positively affect the adsorption, must be improved.

Recovery Strategies for Heavy Metal-Inhibited Biological Nitrogen Removal from Wastewater Treatment Plants: A Review

Biological nutrient removal is an integral part of a wastewater treatment plant. However, the microorganism responsible for nutrient removal is susceptible to inhibition by external toxicants such as heavy metals which have the potential to completely inhibit biological nutrient removal. The inhibition is a result of the interaction between heavy metals with the cell membrane and the deoxyribonucleic acid (DNA) of the cell. Several attempts, such as the addition of pretreatment steps, have been made to prevent heavy metals from entering the biological wastewater systems. However, the unexpected introduction of heavy metals into wastewater treatment plants result in the inhibition of the biological wastewater treatment systems. This necessitates the recovery of the biological process. The biological processes may be recovered naturally. However, the natural recovery takes time; additionally, the biological process may not be fully recovered under natural conditions. Several methods have been explored to catalyze the recovery process of the biological wastewater treatment process. Four methods have been discussed in this paper. These include the application of physical methods, chelating agents, external field energy, and biological accelerants. These methods are compared for their ability to catalase the process, as well as their environmental friendliness. The application of bio-accelerant was shown to be superior to other recovery strategies that were also reviewed in this paper. Furthermore, the application of external field energy has also been shown to accelerate the recovery process. Although EDTA has been gaining popularity as an alternative recovery strategy, chelating agents have been shown to harm the metal acquisition of bacteria, thereby affecting other metabolic processes that require heavy metals in small amounts. It was then concluded that understanding the mechanism of inhibition by specific heavy metals, and understanding the key microorganism in the inhibited process, is key to developing an effective recovery strategy.

Desorption characteristics of phosphate and ammonium from sludge-based biochar

It is effective to adsorb phosphate and ammonium from water by sludge-based biochar, while the desorption performance has not been studied systematically. Biochar in this study was prepared through the co-pyrolysis of sludge and walnut shells to remove NH4+ and PO43- from water. The desorption characteristics of NH4+ and PO43- from the post-adsorption sludge-based biochar were investigated. The effects of the adsorption condition (concentration of adsorption solution) and desorption conditions (pH value of desorption solution and desorption temperature and time) on desorption performance were examined. Several techniques were performed to characterise the properties of the post-adsorption sludge-based biochar. The adsorption amount of the pure sewage sludge biochar (SBC) for PO43- and the biochar derived from the co-pyrolysis of sewage sludge and walnut shell with the mixing ratio of 3:1 (MBC3-1) for NH4+ were 14.19/ 23.75 mg/g and 9.28/ 16.23 mg/g, respectively, when the concentrations of the adsorbates were 100 and 500 mg/L. The desorption experiments showed that the acidic condition (pH = 2) was beneficial for PO43- and NH4+ desorption. The highest desorption ratio reached 7.58% for PO43- and 2.18% for NH4+. The desorption of PO43- was endothermic, whereas that of NH4+ was exothermic. The desorption amounts of PO43- and NH4+ decreased and increased, respectively, with the increase in desorption time. This study of the desorption characteristics of PO43- and NH4+ in sludge-based biochar provides a theoretical basis for the subsequent utilisation of sludge-based biochar.

Recent Developments in the Application of Bio-Waste-Derived Adsorbents for the Removal of Methylene Blue from Wastewater: A Review

Over the last few years, various industries have released wastewater containing high concentrations of dyes straight into the ecological system, which has become a major environmental problem (i.e., soil, groundwater, surface water pollution, etc.). The rapid growth of textile industries has created an alarming situation in which further deterioration to the environment has been caused due to substances being left in treated wastewater, including dyes. The application of activated carbon has recently been demonstrated to be a highly efficient technology in terms of removing methylene blue (MB) from wastewater. Agricultural waste, as well as animal-based and wood products, are excellent sources of bio-waste for MB remediation since they are extremely efficient, have high sorption capacities, and are renewable sources. Despite the fact that commercial activated carbon is a favored adsorbent for dye elimination, its extensive application is restricted because of its comparatively high cost, which has prompted researchers to investigate alternative sources of adsorbents that are non-conventional and more economical. The goal of this review article was to critically evaluate the accessible information on the characteristics of bio-waste-derived adsorbents for MB's removal, as well as related parameters influencing the performance of this process. The review also highlighted the processing methods developed in previous studies. Regeneration processes, economic challenges, and the valorization of post-sorption materials were also discussed. This review is beneficial in terms of understanding recent advances in the status of biowaste-derived adsorbents, highlighting the accelerating need for the development of low-cost adsorbents and functioning as a precursor for large-scale system optimization.

Synthesis, Characterization, and Dye Removal of ZnCl2-Modified Biochar Derived from Pulp and Paper Sludge

In this study, pulp sludge-derived biochar synthesized through modification with ZnCl₂ under multistep pyrolysis conditions was investigated for the effective removal of methylene blue (MB) from aqueous solution. Results showed that when the Zn2PT350-700 dosage was 10 mg, the largest adsorption amount of MB was 590.20 mg/g within 24 h under pH = 8. Kinetics and thermodynamics revealed that the adsorption process of MB can be described by the Freundlich isotherm model and the pseudo-second-order kinetic model, which means that multilayer sorption occurred on the heterogeneous surface of Zn2PT350-700. The analysis of the adsorption mechanism showed that electrostatic attraction between the deprotonated functional groups and MB⁺, cation exchange, and π-electron interaction played a major role in MB adsorption, followed by physical adsorption. After six cycles of desorption-adsorption, Zn2PT350-700 still maintained good adsorption performance. All results demonstrated that Zn2PT350-700 could perform as promising adsorbents for efficient MB removal from wastewater. Using biochar from paper and pulp sludge for wastewater remediation is an ingenious method, which can reduce the environmental and health risks related to industrial waste disposal, while providing remediation of water contaminated with industrial dye effluents.

Artificial intelligence (AI) applications in adsorption of heavy metals using modified biochar

The process of removal of heavy metals is important due to their toxic effects on living organisms and undesirable anthropogenic effects. Conventional methods possess many irreconcilable disadvantages pertaining to cost and efficiency. As a result, the usage of biochar, which is produced as a by-product of biomass pyrolysis, has gained sizable traction in recent times for the removal of heavy metals. This review elucidates some widely recognized harmful heavy metals and their removal using biochar. It also highlights and compares the variety of feedstock available for preparation of biochar, pyrolysis variables involved and efficiency of biochar. Various adsorption kinetics and isotherms are also discussed along with the process of desorption to recycle biochar for reuse as adsorbent. Furthermore, this review elucidates the advancements in remediation of heavy metals using biochar by emphasizing the importance and advantages in the usage of machine learning (ML) and artificial intelligence (AI) for the optimization of adsorption variables and biochar feedstock properties. The usage of AI and ML is cost and time-effective and allows an interdisciplinary approach to remove heavy metals by biochar.

Deciphering the Kinetic Study of Sodium Dodecyl Sulfate on Ag Nanoparticle Synthesis Using Cassia siamea Flower Extract as a Reducing Agent

Silver nanoparticles (Ag NPs) were synthesized using Cassia siamea flower petal extract (CSFE) as a reducing agent for the first time. In its presence and absence, the correlative effects of the anionic surface-active agent sodium dodecyl sulfate (SDS) were studied with respect to the development and texture of Ag NPs. Under different reagent compositions, the Ag NPs were inferred by localized surface plasmon resonance peaks between 419 and 455 nm. In the absence of SDS, there was a small eminence at 290 and around 350 nm, pointing toward the possibility of irregular polytope Ag NPs, which was confirmed in the transmission electron microscopy images. This elevation vanished beyond the cmc of [SDS], resulting in spherical and oval shaped Ag NPs. The effects of reagent concentrations were studied at 25 °C and around 7 and 9 pH in the absence and presence of SDS, respectively. Also, kinetic studies were performed by UV-visible spectrophotometry. Prodigious effects on shape and size were found under different synthesis conditions in terms of hexagonal, rod-, irregular-, and spherical shaped Ag NPs. Furthermore, the antimycotic activity of the synthesized Ag NPs was established on different Candida strains, and best results were found pertaining Candida tropicalis. The ensuing study impels the control of texture and dispersity for Ag NPs by CSFE and SDS, and the resultant polytope Ag NPs could be a future solution for drug-resistant pathogenic fungi.

Sodium Dodecylbenzene Sulfonate-Modified Biochar as An Adsorbent for The Removal of Methylene Blue

Biochar is an interesting adsorbent material due to its use is correlated with biomass waste utilization and also minimize environmental pollution from high amount of biomass by-product. Regarding to improve the biochar ability in water treatment, several surface modifications have been developed, one of them is modification using surfactant. In this study, sodium dodecylbenzene sulfonate (SDBS) was used to modify the surface of biochar prepared from pyrolysis of cassava peels (Manihot utilissima). Its performance in biochar modification to remove methylene blue (MB) dyes was compared with sodium dodecyl sulphate (SDS) surfactant for observing the important of – interactions mechanisms. The analysis of biochar and biochar-SDBS were conducted by using Fourier transform infrared (FTIR), CHNS elemental analysis, and scanning electron microscope (SEM). Furthermore, the adsorption experiments were conducted using UV-Vis spectrophotometer. It is known that modification using SDBS could increase the adsorption capacity of biochar not only from electrostatic interaction but also through – interactions mechanisms. In this respect, as the amount of SDBS mass increased, the adsorption capacity was also improved due to the modification produced more active cites on biochar. The maximum MB adsorption onto biochar-SDBS occurred at adsorbent mass of 15 mg with optimum pH value of 10. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Practical and Sustainable Modification Method on Activated Carbon to Improve the Decolorization Process in the Acetaminophen Pharmaceutical Industry

Decolorization plays an important part in the industrial production of acetaminophen (APAP) drugs. The impurities generated from the APAP pharmaceutical industry decolorization refining process were primarily separated and purified, and their structures were determined by MS and ¹H NMR technology. Then the catalytic effects of three samples of modified powdered activated carbon (PAC) on APAP in heterogeneous solution systems and the adsorption catalysis system were systematically investigated, which indicated that PAC catalyzed the APAP oxidative coupling side reaction and thus increased the impurities in the APAP product. The M-T-RAC (thermal regeneration PAC modified by ammonium sulfate) possessing more acidic surface groups can effectively inhibit this side reaction. Furthermore, according to the different catalytic results of O-T-RAC (thermal regeneration PAC modified by hydrogen peroxide) in solid-liquid catalytic and adsorption catalytic systems, we speculated that the multimer impurities were generated by the oxidative coupling reaction of APAP being oxidized to rated N-acetyl-p-benzoquinone (NAPQI) during decolorization, while free radical polymerization of APAP mainly occurred in the pores of the spent PAC. The pore textural structure and chemical properties of M-T-RAC were further characterized to ensure its feasibility of industrial application. The process of simulating industrial decolorization substantiated the excellent ability of M-T-RAC to inhibit side reactions. This study contributes to the development of green materials for sustainable recycling of activated carbon to reduce pollution and costs, and provides an effective advice for the pharmaceutical process.

Synthesis of silica-composited biochars from alkali-fused fly ash and agricultural wastes for enhanced adsorption of methylene blue

Two types of silica-composited biochars were prepared by mixing swine manure or rice straw with alkali-fused fly ash (AFFA) followed by pyrolysis. A 10% (w/w) AFFA modification improved the specific surface area, pore volume, and average pore size of the biochars. Certain surface oxygen-containing functional groups (i.e., -OH and CO) in the biochars were protected, and silicon-oxygen bonds (i.e., O-Si-O and OSi) were strengthened considerably by AFFA modifications during high-temperature pyrolysis. The adsorption capacity of biochar for methylene blue (MB) was enhanced after AFFA modification, and a modified biochar with the highest adsorption capacity was prepared at a pyrolysis temperature of 700 °C, pyrolysis holding time of 2 h, and an AFFA proportion of 10%. The MB adsorption capacity of the modified biochars significantly increased when the pH of the solution increased (from 3 to 13). The adsorption data were well described by a pseudo-second-order model and Langmuir isotherms. The maximum MB adsorption capacities of the modified swine manure and rice straw biochars were 143.76 mg/g and 131.58 mg/g, respectively. The adsorption capacities of the AFFA-modified biochars were 10.7-112.3% higher than those of the unmodified biochars. The enhanced MB adsorption capacities of the former appear to be attributed to their increased specific surface areas, increased porosities, strong oxygen-containing functional groups, and high contents of exchangeable sodium ions. These results indicate that industrial and agricultural wastes can be reused to produce novel silica-composited biochars with high MB removal capacity. Accordingly, these biochars could be effectively used to treat wastewater and thus to mitigate solid waste disposal-related problems.

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.

Adsorption of Methylene Blue in Water onto Activated Carbon by Surfactant Modification

In this paper, the enhanced adsorption of methylene blue (MB) dye ion on the activated carbon (AC) modified by three surfactants in aqueous solution was researched. Anionic surfactants—sodium lauryl sulfate (SLS) and sodium dodecyl sulfonate (SDS)—and cationic surfactant—hexadecyl trimethyl ammonium bromide (CTAB)—were used for the modification of AC. This work showed that the adsorption performance of cationic dye by activated carbon modified by anionic surfactants (SLS) was significantly improved, whereas the adsorption performance of cationic dye by activated carbon modified by cationic surfactant (CTAB) was reduced. In addition, the effects of initial MB concentration, AC dosage, pH, reaction time, temperature, real water samples, and additive salts on the adsorption were studied. When Na+, K+, Ca2+, NH4+, and Mg2+ were present in the MB dye solution, the effect of these cations was negligible on the adsorption (<5%). The presence of NO2- improved the adsorption performance significantly, whereas the removal rate of MB was reduced in the presence of competitive cation (Fe2+). It was found that the isotherm data had a good correlation with the Langmuir isotherm through analyzing the experimental data by various models. The dynamics of adsorption were better described by the pseudo-second-order model and the adsorption process was endothermic and spontaneous. The results showed that AC modified by anionic surfactant was effective for the adsorption of MB dye in both modeling water and real water.

Design and Preparation of Chitosan-Crosslinked Bismuth Ferrite/Biochar Coupled Magnetic Material for Methylene Blue Removal

Biochar obtained by pyrolysis of the fiber plant kenaf was mixed with bismuth ferrite (BiFeO₃) in a chitosan-containing acetic acid solution, magnetized, and modified to prepare a chitosan-crosslinked BiFeO₃/biochar coupled magnetic material. The adsorption properties of the composite were investigated using methylene blue dissolved in water, and the effects of external conditions, such as pH, methylene blue concentration, reaction time, and temperature, on the adsorption performance were studied. The adsorption data were fitted and analyzed with kinetic and isotherm models, and the results showed that the BiFeO₃/biochar coupled magnetic material effectively adsorbed methylene blue. The amounts adsorbed onto this magnetic material increased with increasing initial methylene blue concentration, reaction time, and temperature, and the adsorption performance improved under neutral and alkaline conditions. The pseudo-first-order kinetic and Langmuir isotherm models satisfactorily fitted the adsorption data, showing that the adsorption of methylene blue involved both chemical and physical adsorption. The maximum adsorption capacity of methylene blue onto the BiFeO₃/biochar coupled magnetic material reached 18.942 mg·g⁻¹ at 25 °C, confirming the excellent dye binding activity of this material.

Adsorption of Bisphenol A on Peanut Shell Biochars: The Effects of Surfactants

Bisphenol A (BPA) is a typical endocrine-disrupting chemical. The removal of BPA has raised much concerns in recent years. This paper examined the adsorption behavior of BPA to biochars and the different effects of cationic, anionic, and nonionic surfactants. The results indicated that peanut shell biochars prepared at 300°C (BC300), 500°C (BC500), and 700°C (BC700) showed strong adsorption affinity for BPA, and the adsorption affinity of biochars increased with the increase of pyrolysis temperature. The range of log Kd values was 2.83∼3.71, 2.91∼4.57, and 3.24∼5.50 for BC300, BC500, and BC700, respectively. Both the type of surfactants and the properties of biochars could affect the adsorption behavior of BPA. Cetyltrimethyl ammonium bromide (CTAB) showed negligible effect on the adsorption of BPA on BC300, and the inhibition effect of CTAB was stronger with the increase of biochar pyrolysis temperature. Tween 20 and sodium dodecyl benzene sulfonate (SDBS) showed stronger inhibition effect than CTAB, especially on BC300. This is likely because the inhibition effect caused by competition of CTAB may be counterbalanced by the enhancement caused by the partitioning effect by adsorbed CTAB and the bridge effect between the –NH4+ group of CTAB and the phenol group on BPA/O-functional groups of biochars, whereas Tween 20 and SDBS do not have this bridge effect advantage. This study could provide insightful information for the application of biochars in removal of BPA.