Adsorption of methylene blue on chemically modified lychee seed biochar: Dynamic, equilibrium, and thermodynamic study

Identification of influential parameters and conditions in heavy metals adsorption onto Cal-LDH-PC using optimization approaches of RSM and Taguchi

Adsorption process plays an important role in the remediation of heavy metals (HMs) from wastewater. A laboratory trial was conducted to investigate effective parameters for improving the bio-adsorption removal of HMs. SEM, EDX, BET, and FTIR techniques were applied to characterize the calcined layer double hydroxide (Cal-LDH), pectin (PC), and Cal-LDH-PC composite prepared from Licorice pomace. The adsorption of zinc (Zn) cadmium, nickel (Ni) and lead (Pb) onto the most efficient sorbent was investigated using RSM methodology with operational factors such as concentration, reaction time, sorbent dose, and pH. The results related to FTIR showed that Cal-LDH-PC had the highest number of functional groups. Based on the SEM results Cal-LDH had a low surface area (9.36 m2 g-1) and a small pore size (9.22 nm). After the modification process (Cal-LDH-PC), the values of surface area and pore size increased by 13-fold (120 m2 g-1) and 1.5-fold (18 nm), respectively. Cal-LDH had high adsorption performance, more cavities, stability, various functional groups, and excessive carbon and oxygen content, which make it efficient and powerful in removing HMs from wastewater. The optimal condition for achieving the removal efficiency (RE%) values of metals was determined to be 80.79 mg L-1, 100 min, 0.167 g L-1, and 9 for concentration, reaction time, sorbent dose, and pH, respectively. Maximum adsorption capacity and RE (%) were 300 mg g-1 and 99% for Zn. According to the results concentration had a major impact on RE% (except for Ni), while for Ni, adsorbent dose had the most significant impact. The present study introduced Cal-LDH-PC prepared from Licorice pomace as a capable, useful and economical sorbent for HMs removal from polluted environments. Taguchi's statistical method is distinguished as an economic method with easier interpretation, while the RSM approach is more accurate, and it can also check the interaction of parameters.

Eco-friendly engineering of micro composite-based hydroxyapatite bio crystal and polyaniline for high removal of OG dye from wastewater: Adsorption mechanism and RSM@BBD optimization

The presence of harmful substances such as dyes in water systems poses a direct threat to the quality of people's lives and other organisms living in the ecosystem. Orange G (OG) is considered a hazardous dye. The existing paper attempts to evaluate a low-cost adsorbent for the effective removal of OG dye. The developed adsorbent Polyaniline@Hydroxyapatite extracted from Cilus Gilberti fish Scale (PANI@FHAP) was elaborated through the application of the in situ chemical polymerization method to incorporate PANI on the surface of naturally extracted hydroxyapatite FHAP. The good synthesis of PANI@FHAP was evaluated through multiple techniques including X-ray diffraction (XRD), Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS), Fourier Transforms Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) coupled with thermal differential analysis (DTA) analysis. The results reveal a highly ordered disposition of PANI chains on FHAP, resulting in a well-coated FHAP in the PANI matrix. Furthermore, the presence of functional groups on the surface of PANI such as amine (-NH2) and imine (=NH) groups would facilitate the removal of OG dye from contaminated water. The adsorption of OG onto PANI@FHAP was conducted in batch mode and optimized through response surface methodology coupled with box-Behnken design (RSM/BBD) to investigate the effect of time, adsorbent dose, and initial concentration. The outcomes proved that OG adsorption follows a quadratic model (R2 = 0.989). The kinetic study revealed that the adsorption of OG fits the pseudo-second-order model. On the other hand, the isotherm study declared that the Freundlich model is best suited to the description of OG adsorption. For thermodynamic study, the adsorption of OG is spontaneous in nature and exothermic. Furthermore, the regeneration-reusability study indicates that PANI@FHAP could be regenerated and reused up to five successive cycles. Based on the FTIR spectrum of PANI@FHAP after OG adsorption, the mechanism governing OG adsorption is predominantly driven by π-π interaction, electrostatic interaction, and hydrogen bonding interactions. The obtained results suppose that PANI@FHAP adsorbent can be a competitive material in large-scale applications.

Valorization of non-edible fruit seeds into valuable products: A sustainable approach towards circular bioeconomy

Global imperatives have recently shown a paradigm shift in the prevailing resource utilization model from a linear approach to a circular bioeconomy. The primary goal of the circular bioeconomy model is to minimize waste by effective re-usage of organic waste and efficient nutrient recycling. In essence, circular bioeconomy integrates the fundamental concept of circular economy, which strives to offer sustainable goods and services by leveraging biological resources and processes. Notably, the circular bioeconomy differs from conventional waste recycling by prioritizing the safeguarding and restoration of production ecosystems, focusing on harnessing renewable biological resources and their associated waste streams to produce value-added products like food, animal feed, and bioenergy. Amidst these sustainability efforts, fruit seeds are getting considerable attention, which were previously overlooked and commonly discarded but were known to comprise diverse chemicals with significant industrial applications, not limited to cosmetics and pharmaceutical industries. While, polyphenols in these seeds offer extensive health benefits, the inadequate conversion of fruit waste into valuable products poses substantial environmental challenges and resource wastage. This review aims to comprehend the known information about the application of non-edible fruit seeds for synthesising metallic nanoparticles, carbon dots, biochar, biosorbent, and biodiesel. Further, this review sheds light on the potential use of these seeds as functional foods and feed ingredients; it also comprehends the safety aspects associated with their utilization. Overall, this review aims to provide a roadmap for harnessing the potential of non-edible fruit seeds by adhering to the principles of a sustainable circular bioeconomy.

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

Application of Activated Carbons Obtained from Polymer Waste for the Adsorption of Dyes from Aqueous Solutions

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO2, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm's titration method, and pHpzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (qm exp) of MB and MG (349 mg g-1 and 274 mg g-1, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents.

Reshaping environmental sustainability: Poultry by-products digestate valorization for enhanced biochar performance in methylene blue removal

Anaerobic digestion is a highly effective and innovative method for treating organic waste while simultaneously generating energy. However, the treatment of the resulting digestate remains a challenging endeavor. To address this issue, poultry by-products digestate is used in this study to prepare biochars at two different pyrolysis temperatures (500/600 °C). Despite their potential, the utilization of untreated biochar is restricted due to its inadequate adsorption capacity. Therefore, each biochar was chemically activated using either HNO3 or KOH to synthesize four activated biochars (BC5@KOH, BC6@HNO3, BC5@HNO3, and BC6@HNO3). The aim is to investigate how the nature of chemical activation and pyrolysis temperature influence the adsorption of methylene blue dye. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Raman analysis, and pHpzc determination, were exploited to comprehensively elucidate the structure and composition of both unprocessed and chemically activated biochars. Among the activated biochars, the adsorbent BC5@HNO3 exhibits the highest methylene blue (MB) adsorption capacity, reaching 101.72 mg.g-1 at 298 K under (pH = 2, ads dose = 0.6 g.L-1, shaking time of 20 min, as optimal conditions for MB adsorption. Adsorption data for each adsorbent strongly aligns with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Moreover, the thermodynamic study reveals that the adsorption process was endothermic and spontaneous. The adsorption mechanism of MB dye was explored using various analytical techniques, including FTIR, SEM, PZC, and pH impact assessment. The findings suggest correlations with electrostatic interactions, hydrogen bonding, pore filling, as well as n-π and π-π interactions. Apparently, activated biochars play a crucial role in efficiently removing methylene blue dye, showcasing their potential as environmentally friendly and effective adsorbents.

Annona glabra L. Seeds: An Agricultural Waste Biosorbent for the Eco-Friendly Removal of Methylene Blue

The seeds of Annona glabra L., an invasive plant in Vietnam, were first employed as a new biosorbent for the adsorption of methylene blue (MB) from aqueous media. The characterizations of the material using FT-IR, SEM, nitrogen adsorption-desorption analysis, and point of zero charge reveals that it possesses a rough and irregular surface, various polar functional groups, and pHpzc of 5.5. Certain adsorption conditions including adsorbent dose, solution pH, contact time, and initial concentration of MB were found to affect adsorption efficiency. The kinetic data are well fitted with pseudo-second-order model with the adsorption rate of 0.002 g mg-1 min-1 and initial rate of 4.46 mg g-1 min-1. For the adsorption isotherm, three nonlinear models were used to analyze the experiment data, including Langmuir, Freundlich, and Temkin. The results indicate that the Langmuir model best describes the adsorption of Annona glabra L. seeds powder (AGSP) with a maximum adsorption capacity of 98.0 mg g-1. The investigation underpins the adsorption mechanism, whereby the electrostatic attraction between positively charged MB and negatively charged surface of AGSP is expected to be the predominant mechanism, together with hydrogen bonding and pi-pi interaction. These results make AGSP an interesting biosorbent concerning its environmental friendliness, cost-effectiveness, and relatively high dye adsorption capacity.

In-situ growth of zinc sulfide on the surface of alginate-based biomass carbon: A new material for removing methylene blue/basic fuchsin and copper ions

This work aims to prepare a composite adsorbent with a fixed shape to improve the performance of carbon materials and to solve the problem of adsorbent in powder form which is difficult to recycle after use. The BC-ZnS composite system was successfully prepared by hydrothermal method based on the preparation of biomass carbon (BC) using alginate (Alg), while the ZnS component was grown in-situ on the surface of BC. The effects of Alg, Zn source, hydrothermal temperature and time on the synthesis of BC-ZnS were explored, the results indicated that ZnS was successfully grown in-situ on the BC surface, while the BC maintained its original morphology. BC-ZnS showed excellent adsorption capacity for methylene blue (MB), basic fuchsin (BF), and copper ions (Cu2+), reaching 301.50 mg/g for MB and exhibiting good cyclic stability. The adsorption of MB/BF/Cu2+ by BC-ZnS was characterized by the presence of multiple forces, where the BC component mainly depended on the electrostatic force of Alg residue, while the ZnS involves electrostatic forces, ion exchange and Lewis acid/base soft-soft interactions. The adsorption process conforms to pseudo-first-kinetics and is a spontaneous entropy-increasing process. BC-ZnS can be a candidate for reusable wastewater treatment and has excellent potential for application.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

On the adsorption characteristics and mechanism of methylene blue by ball mill modified biochar

In this study, modified biochar (BRB) was prepared from rice straw by ball milling technique and used for the adsorption of methylene blue (MB) in wastewater. The BRB was characterized by SEM, FTIR and XPS, and the adsorption model and Box-Behnken design were used to optimize the five influencing factors. The results showed that the ball milling technique could increase the content of functional groups (-OH, C=C and C-O, etc.) and aromatic structures on the surface of biochar, thus facilitating the removal of MB. The isotherm model was consistent with the Langmuir adsorption model (R2 = 0.947) and the maximum adsorption capacity was 50.27 mg/g. The adsorption kinetics was consistent with the pseudo-second-order kinetic model (R2 = 1) and the adsorption rate was mainly controlled by chemisorption. The thermodynamic model confirmed that the adsorption process was a spontaneous heat absorption reaction. The maximum adsorption efficiency was 99.78% under the optimal conditions (40℃, pH 8, reaction time = 90 min, dosing amount = 0.1 mg), and the adsorption efficiency could be improved by increasing the pH and BRB dosing amount. The surface functional groups and crystal structure properties of BRB were the main determinants of adsorption, and it was clarified that physical adsorption, electrostatic attraction and π-π interaction were the main mechanisms for the adsorption of MB by BRB. The main mechanisms were clarified. Therefore, BRB is an economic, efficient and green adsorption material with good potential for the removal of dye pollutants in the aqueous environment.

Conversion of solid wastes and natural biomass for deciphering the valorization of biochar in pollution abatement: A review on the thermo-chemical processes

This overview addresses the formation of solid trash and the various forms of waste from a variety of industries, which environmentalists have embraced. The paper investigates the negative effects on the environment caused by unsustainable management of municipal solid trash as well as the opportunities presented by the formal system. This examination looks at the origins of solid waste as well as the typical treatment methods. Pyrolysis methods, feedstock pyrolysis, and lignocellulosic biomass pyrolysis were highlighted. Explain in detail the various thermochemical processes that take place during the pyrolysis of biomass. Due to its carbon content, low cost, accessibility, ubiquitousness, renewable nature, and environmental friendliness, biomass waste is a unique biochar precursor. This study looks at the different types of biomass waste that are available for treating wastewater. This study discussed a wide variety of reactors. Adsorption is the standard method that is used the most frequently to remove hazardous organic, dye, and inorganic pollutants from wastewater. These pollutants cause damage to the environment and water supplies, thus it is important to remove them. Adsorption is both simple and inexpensive to utilize. Temperature-dependent conversions explain the kinetic theories of biomaterial biochemical degradation. This article presents a review that explains how pyrolytic breakdown char materials can be used to reduce pollution and improve environmental management.

Synthesis and characterization of PANI-ZrWPO4 nanocomposite: adsorption-reduction efficiency and regeneration potential for Cr(VI) removal

A novel polyaniline zirconium tungstophosphate (PANI-ZrWPO4) nanocomposite was successfully synthesized through an in situ oxidative polymerization reaction followed by a microwave irradiation process. The synthesized nanocomposite was characterized by using FESEM, EDX, TEM, XRD, FTIR, Raman, TGA-DTA, XPS, and N2 adsorption-desorption analysis and chemical analysis to know about the formation of material. The results of the FTIR and Raman spectra confirmed that the conducting PANI polymer interacted with ZrWPO4 to form the PANI-ZrWPO4 nanocomposite. The XRD data showed that the composite had a crystalline nature. The TEM and FESEM images revealed that polyaniline had formed on the exterior of the PANI-ZrWPO4 nanocomposite. Further investigation was done on the efficiency of the PANI-ZrWPO4 nanocomposite as an adsorbent for Cr(VI) removal through batch adsorption experiments. The maximum Langmuir adsorption capacity of PANI-ZrWPO4 was found to be 71.4 mg g-1. The removal of Cr(VI) was optimized with the six variables namely adsorbent dose, initial concentration, Time, pH, Temperature, and stirring rate using the Box-Behnken design (BBD) model. The XPS spectra confirmed simultaneously adsorption reduction occurs Cr(VI) to Cr(III) through in situ chemical reduction. Moreover, the regeneration efficiency of PANI-ZrWPO4 was studied, and it was found to be able to remove around 80% of Cr(VI) even after five cycles, demonstrating its potential as an effective and reusable adsorbent.

Adsorption kinetics of ciprofloxacin and ofloxacin by green-modified carbon nanotubes

This paper investigated the uptake of CIP and OFL in single and multicomponent adsorptive systems using modified carbon nanotubes (CNTs) as adsorbent material. The characterization analyses of the pre- and post-process material by XPS, TG/DTG, FT-IR, SEM/EDS, and XRD helped in the elucidation of the mechanisms, indicating greater involvement of n-n and π -π interactions. In the kinetic studies, the simple systems with CIP and OFL were similar, both showed equilibrium time around 20/30 min and increased adsorptive capacity with increasing initial drug concentration. In the multicomponent system, different fractions of CIP and OFL were tested and the time to reach equilibrium also varied between 20 and 30 min. In general, the adsorption capacity of CIP is slightly lower than that of OFL under the conditions tested. The selectivity analysis of the system showed that the selectivity's of the two drugs are identical in equimolar fractions. The mathematical modeling of the kinetic data indicated that in monocomponent systems, the model of pseudo-second order (PSO) adequately described both CIP and OFL kinetics. Furthermore, with the implementation of Artificial Neural Networks (ANN), it was possible to obtain a more assertive prediction of the behavior of single and binary systems.

Enhanced Reactive Brilliant Blue Removal Using Chitosan-Biochar Hydrogel Beads

To address the challenges associated with the weak affinity and difficult separation of biochar, we developed chitosan-biochar hydrogel beads (CBHBs) as an efficient solution for removing reactive brilliant blue (RBB KN-R) from wastewater. The adsorption behavior and mechanism of RBB KN-R onto CBHBs were extensively studied. Notably, the adsorption capacity of RBB KN-R showed pH-dependence, and the highest adsorption capacity was observed at pH 2. The adsorption process was well fitted with the pseudo-second-order kinetic model and the intraparticle diffusion model. Film diffusion and intraparticle diffusion were both responsible for the adsorption of RBB KN-R onto CBHBs. At 298.15 K, the maximum adsorption capacity qm was determined to be 140.74 mg/g, with higher temperatures favoring the adsorption process. A complex mechanism involving π-π interactions, electrostatic attraction, hydrophobic interaction, and hydrogen bonding was found to contribute to the overall adsorption process. The experimental data discovered the coexisting substances and elevated ionic strength hindered the adsorption capacity. Significantly, after three cycles of adsorption-desorption, the CBHBs maintained an adsorption capacity above 95% for RBB KN-R. These promising results imply that CBHBs are a durable and cost-effective adsorbent for efficient removal of dyes from wastewater.

Propensity of a low-cost adsorbent derived from agricultural wastes to interact with cationic dyes in aqueous solutions

Ash collected from thrown-away by-products while preparing a popular traditional food additive, kolakhar of the Assamese community of North East, India, was used as an alternate cost-effective, porous bioadsorbent option from the conventional activated carbon for the purification of carcinogenic dyes laden water. The base material for kolakhar preparation was taken from the discarded banana stem waste to stimulate agricultural waste management. Methylene blue (MB) and basic fuchsin (BF) dyes were used as model cationic dyes. Characterization techniques like CHN, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET) analysis of the prepared banana stem ash (BSA) reveal the presence of high inorganic contents and functional groups in the irregular, porous bioadsorbent with surface area 55.534 m2 g-1. Various regulating parameters studied to optimize the adsorption capacity of BSA were bioadsorbent dose (0.1-3 g/L), temperature (298-318 K), contact time (0-150 min), pH (2-9), and initial dye concentrations (10-40 mg/L). Non-linear kinetic models suggested Elovich for both MB and BF adsorption, while the non-linear isotherm model suggested Langmuir and Temkin for MB and BF adsorption, respectively, as best-fitted curves. The monolayer adsorption capacity (qm) for MB and BF was 15.22 mg/g and 24.08 mg/g at 318 K, respectively, with more than 95% removal efficiency for both dyes. The thermodynamic parameters studied indicated that the adsorption is spontaneous. The ∆H0 values of MB and BF adsorptions were 2.303 kJ/mol (endothermic) and - 29.238 kJ/mol (exothermic), respectively.

Magnetic Fe3O4 nanoparticles loaded guava leaves powder impregnated into calcium alginate hydrogel beads (Fe3O4-GLP@CAB) for efficient removal of methylene blue dye from aqueous environment: Synthesis, characterization, and its adsorption performance

In the present work, a novel Fe3O4-GLP@CAB was successfully synthesized via a co-precipitation procedure and applied for the removal of methylene blue (MB) from aqueous environment. The structural and physicochemical characteristics of the as-prepared materials were explored using a variety of characterization methods, including pHPZC, XRD, VSM, FE-SEM/EDX, BJH/BET, and FTIR. The effects of several experimental factors on the uptake of MB using Fe3O4-GLP@CAB were examined through batch experiments. The highest MB dye removal efficiency of Fe3O4-GLP@CAB was obtained to be 95.2 % at pH 10.0. Adsorption equilibrium isotherm data at different temperatures showed an excellent agreement with the Langmuir model. The adsorption uptake of MB onto Fe3O4-GLP@CAB was determined as 136.7 mg/g at 298 K. The kinetic data were well-fitted by the pseudo-first-order model, indicating that physisorption mainly controlled it. Several thermodynamic variables derived from adsorption data, like as ΔGo, ΔSo, ΔHo, and Ea, accounted for a favourable, spontaneous, exothermic, and physisorption process. Without seeing a substantial decline in adsorptive performance, the Fe3O4-GLP@CAB was employed for five regeneration cycles. Because they can be readily separated from wastewater after treatment, the synthesized Fe3O4-GLP@CAB was thus regarded as a highly recyclable and effective adsorbent for MB dye.

Adsorption of Cd (II) by a novel living and non-living Cupriavidus necator GX_5: optimization, equilibrium and kinetic studies

Biosorbents have been extensively studied for heavy metal adsorption due to their advantages of low cost and high efficiency. In the study, the living and non-living biomass of Cupriavidus necator GX_5 previously isolated were evaluated for their adsorption capacity and/or removal efficiency for Cd (II) through batch experiments, SEM and FT-IR investigations. The maximum removal efficiency rates for the live and dead biomass were 60.51% and 78.53%, respectively, at an optimum pH of 6, a dosage of 1 g/L and an initial Cd (II) concentration of 5 mg/L. The pseudo-second-order kinetic model was more suitable for fitting the experimental data, indicating that the rate-limiting step might be chemisorption. The Freundlich isotherm model fit better than the Langmuir isotherm model, implying that the adsorption process of both biosorbents was heterogeneous. FT-IR observation reflected that various functional groups were involved in Cd (II) adsorption: -OH, -NH, C=O, C-O and C-C groups for the living biomass and -OH, -NH, C-H, C = O, C-N and N-H groups for the dead biomass. Our results imply that non-living biosorbents have a higher capacity and stronger strength for absorbing Cd (II) than living biomass. Therefore, we suggest that dead GX_5 is a promising adsorbent and can be used in Cd (II)-contaminated environments.

Hungarian and Indonesian rice husk as bioadsorbents for binary biosorption of cationic dyes from aqueous solutions: A factorial design analysis

The wastewater of the dye industry can be characterized by a complex chemical composition and consists of numerous dyes. Bioadsorbents are increasingly applied for the biosorption of dyes because they are inexpensive and environmentally friendly. Rice husk (RH) is a potential agricultural waste that can be converted into a bioadsorbents for the biosorption of cationic dyes. Herein, the removal of methylene blue (MB) and basic red 9 (BR9) dyes by Hungarian rice husk (HRH) and Indonesian rice husk (IRH) using binary biosorption was investigated. Adsorbents were characterized by zeta potential, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Batch biosorption evaluated the influence of different variables, including pH, adsorbent dose, contact time, and initial concentrations. Several factors that influence the biosorption of MB and BR9 onto rice husk were assessed using main effect, Pareto charts, normal probability plots, and interaction effect in a factorial design. The optimum contact time was 60 min. Isotherm and kinetic models of MB and BR9 in binary biosorption fitted to the Brunauer-Emmett-Teller multilayer and the Elovich equation based on correlation coefficients and nonlinear chi-square. Results showed that the biosorption capacity of HRH was 10.4 mg/g for MB and 10 mg/g for BR9; values for IRH were 9.3 mg/g and 9.6 mg/g, respectively. Therefore, HRH and IRH were found to be effective adsorbents for removing MB and BR9 via binary biosorption.

Modified biochar prepared from Retinervus luffae fructus for dyes adsorption and aerobic sludge granulation

Retinervus luffae fructus biochar (RLFB) and ZnCl2 pretreated Retinervus luffae fructus biochar (ZRLFB) were prepared by pyrolysis. The as-prepared biochar was investigated for its applicability as a dye adsorber using sunset yellow (SY) and basic red 46 (BR46) dyes. Additionally, ZRLFB was used for the experimental cultivation of granular sludge. The results indicated that the adsorption effect of ZRLFB on the two dyes was higher than RLFB. The adsorption of RLFB to SY was related to the Langmuir and Freundlich models, whereas the adsorption of RLFB-BR46, ZRLFB-SY, and ZRLFB-BR46 was more in line with the Langmuir model. The adsorption process of dyes on two kinds of biochars can be described using pseudo-second-order mechanisms. The maximum adsorption capacity obtained was 1.9586 (RLFB-SY), 6.1286 (RLFB-BR46), 49.2611 (ZRLFB-SY), and 181.4882 mg g^-1 (RLFB-BR46). The result of the SBR operation showed that ZRLFB can potentially be applied as the core of aerobic granular sludge.

Sustainable green conversion of coal gangue waste into cost-effective porous multimetallic silicate adsorbent enables superefficient removal of Cd(II) and dye

Converting solid wastes into new materials for wastewater decontamination is a feasible "one stone, three birds" strategy to achieve sustainable value-added utilization of resources and minimize waste emissions, but significant challenges remain. In response to this, we proposed an efficient "mineral gene reconstruction" method to synchronously transform coal gangue (CG) into a green porous silicate adsorbent without using any harmful chemicals (i.e., surfactants, organic solvents). The one of the synthesized adsorbents with a high specific surface area (582.28 m²/g) and multimetallic active centres shows outstanding adsorption performance (adsorption capacities: 168.92 mg/g for Cd(II), 234.19 mg/g for methylene blue (MB); removal rate: 99.04% for Cd(II) and 99.9% for MB). The adsorbent can also reach a high removal rate of 99.05%∼99.46% and 89.23%∼99.32% for MB and Cd(II) in real water samples (i.e., Yangtze River, Yellow River, seawater and tap water), respectively. After 5 adsorption-desorption cycles, the adsorption efficiency remained above 90%. The adsorbents mainly adsorbed Cd(II) by electrostatic attraction, surface complexation and partial ion exchange and MB by electrostatic and hydrogen bonding interactions. This study provides a sustainable and promising platform for developing a new-generation cost-efficient adsorbent from waste for clean water production.

Efficient removal of Congo red and methylene blue using biochar from Medulla Tetrapanacis modified by potassium carbonate

Biochar (BC) prepared from Medulla Tetrapanacis was recognized as having potential in environmental remediation because of its porous texture, abundant chemical surface groups and mineral composition. In this study, a novel modified biochar (KBC) derived from Medulla Tetrapanacis achieved efficient adsorption of Congo red (CR) and methylene blue (MB). Characterization results suggested that the modification had little effect on the group distribution of KBC, but a dramatic expansion of specific surface area was observed on KBC (1180.45 m2/g) compared to BC (198.51 m2/g). KBC exhibited a maximum sorption of 584.17 mg/g for CR and 318.01 mg/g for MB. Kinetic and isotherm studies revealed sorption of CR and MB by KBC was chemosorption, which occurred on the monolayer surface. The comprehensive analysis also provided the basis for the application of KBC to practical production. These outcomes suggested that KBC may become a new option for the effluent treatment.

Green Synthesis and Characteristics of Cellulose Nanocrystal/Poly Acrylic Acid Nanocomposite Thin Film for Organic Dye Adsorption during Water Treatment

Nanocellulose shows potential as an effective natural adsorbent for removing harmful contaminants from wastewater. This paper describes the development of innovative nanocellulose thin films made of cellulose nanocrystals (CNCs), polyacrylic acid (PAA), and active carbon (AC) as adsorbent materials for absorbing azo dyes from wastewater. The CNCs were recovered from sugarcane bagasse using alkali treatment and acid hydrolysis. The composition and processing parameters of the thin films were optimized, and their adsorption capacity was determined using thermodynamic isotherms and adsorption kinetics. Adsorption characteristics such as the methylene blue (MB) dye concentration, contact time, temperature, and pH were investigated to determine how they affected adsorption. The results show that the adsorption process follows pseudo-second-order kinetics. At an adsorbent mass of 50 mg, dye concentration of 50 ppm in 50 mL, and contact period of 120 min at 25 °C, the thin film comprising 64 wt% CNC, 16 wt% PAA, and 20 wt% AC showed high dye removal efficiency (86.3%) and adsorption capacity (43.15 mg/g). The MB removal efficiency increased to 95.56% and the adsorption capacity to 47.78 mg/g when the medium's pH was gradually increased from neutral to alkaline. The nontoxicity, low production cost, water stability, easy recovery, and high adsorption capacity of these membranes make them suitable for water treatment systems.

Hydrogen Peroxide/Phosphoric Acid Modification of Hydrochars for Sulfamethoxazole and Carbamazepine Adsorption: The Role of Oxygen-Containing Functional Groups

Emerging pollutants, such as sulfonamide antibiotics and pharmaceuticals, have been widely detected in water and soils, posing serious environmental and human health concerns. Thus, it is urgent and necessary to develop a technology for removing them. In this work, a hydrothermal carbonization method was used to prepare the hydrochars (HCs) by pine sawdust with different temperatures. To improve the physicochemical properties of HCs, phosphoric acid (H₃PO₄) and hydrogen peroxide (H₂O₂) were used to modify these HCs, and they were referred to as PHCs and HHCs, respectively. The adsorption of sulfamethoxazole (SMX) and carbamazepine (CBZ) by pristine and modified HCs was investigated systematically. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicated that the H₂O₂/H₃PO₄ modification led to the formation of a disordered carbon structure and abundant pores. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy results suggested that carboxyl (-COOH) and hydroxyl (-OH) functional groups of HCs increased after modification, which is the main reason for the higher sorption of SMX and CBZ on H₃PO₄/H₂O₂-modified HCs when compared with pristine HCs. In addition, the positive correlation between -COOH/C=O and logK_d of these two chemicals also suggested that oxygen-containing functional groups played a crucial role in the sorption of SMX and CBZ. The strong hydrophobic interaction and π-π interaction between CBZ and pristine/modified HCs resulted in its higher adsorption when compared with SMX. The results of this study provide a novel perspective on the investigation of adsorption mechanisms and environmental behaviors for organic contaminants by pristine and modified HCs.

Graphene oxide incorporated cellulose acetate beads for efficient removal of methylene blue dye; isotherms, kinetic, mechanism and co-existing ions studies

In this investigation, new porous adsorbent beads were formulated via the incorporation of graphene oxide (GO) into cellulose acetate beads (CA) for the adsorptive removal of methylene blue (MB) dye. The experimental results signified that the adsorption of MB dye increased with the increase in the GO ratio from 10 to 25%. In addition, the adsorption process obeyed PSO kinetic model and Langmuir isotherm model with a maximum adsorption capacity reaching 369.85 mg/g. More importantly, it was proposed that the adsorption mechanism of MB dye onto GO@CA proceeded via electrostatic interactions, H-bonding, van der Waals forces, n-π and π -π interactions. Besides, the fabricated beads exhibited an excellent ability to recycle and reuse after five successive cycles. In addition, there was a high selectivity of GO@CA beads towards MB molecules in the presence of co-existing cations such as Fe2+, Zn2+, Cu2+ and Ni2+.

Adsorption of anionic and cationic dyes in aqueous solution by a sustainable and low-cost activated carbon based on argan solid waste treated with H3PO4

The objective of this work is to study the adsorption capacity of a natural and low-cost material prepared from argan waste treated with H₃PO₄ towards two dyes of different molecular charges and presenting an acute toxicity, the methyl orange (MO, anionic dye) and the methylene blue (MB, cationic dye). The prepared adsorbent was characterized by SEM, EDX, FTIR, and BET specific surface. These analyses showed the presence of C (42%), O (55%), and P (3%) and a remarkable difference between the morphology of the precursor and that of the obtained material with a specific surface of 475 m²/g and a very porous structure as well as the main functional groups, O-H, C=O, and C-H. The influence of the pH showed a maximum adsorption at pH =2 for MO and at pH = 10 for MB. Investigation of the effect of time on the adsorption of anionic and cationic dyes revealed that the contact time at equilibrium was 240 and 180 min, respectively. The isotherms that best fit the adsorption of MO and MB are the Langmuir model and the Freundlich model respectively. The kinetic study showed that the experimental data are in agreement with the pseudo-second-order model. Regeneration of the saturated material was also studied for the probability of reusing the adsorbent in many experiments. The valorization of argan waste into activated carbon using H₃PO₄ has allowed to obtain an effective adsorbent for the removal of anionic and cationic dyes and create an added value for environmental sustainability.

Hierarchical porous biochar from kelp: Insight into self-template effect and highly efficient removal of methylene blue from water

Biochar is known to efficiently remove dyes especially for biochar with hierarchical pores and partial N-species. Here, a facile pyrolysis is used to yield N-doped biochar from kelp without additives, showing surface areas of 771 m2/g as temperature up to 1000 °C and hierarchical small-sized mesopores (2-4 nm) and wide meso-macropores (8-60 nm). A possible self-template mechanism from inorganics is proposed to form hierarchical pore architecture in biochar and used for methylene blue (MB) removal. Biochar pyrolyzed at 1000 °C is found to be efficient for MB removal with uptake of 379.8 mg/g under ambient conditions, one of the largest ever recorded uptakes for other biochar without activation, owing to synergistic effects of high surface areas, mesopores, and graphitized N-species. These results confirm that a facile pyrolysis for transformation of kelp into efficient dyes adsorbent is a cost-effective process for economic and environmental protection.

Novel polyamide/silica/chitosan covalent hybrid: One-step BIC/sol-gel preparation at room temperature and dual applications in Hg2+ electrochemical probing and dye adsorption

Room-temperature preparation of polymer-based covalent hybrids, which with multiple functional characteristics, is instrumental to overcome the performance shortcomings of single-polymer materials and broaden their applications thus. Herein, by introducing chitosan (CS) as a starting substrate into benzoxazine-isocyanide chemistry (BIC)/sol-gel reaction system, a novel polyamide (PA)/SiO₂/CS covalent hybrid (PA-Si-CS) was successfully prepared in-situ at 30 °C. PA-Si-CS's chemical structure and elementary properties were characterized here. The introduction of CS combining with the presence of diverse N, O-containing segments (amide, phenol -OH, Si-OH, etc.) in PA-Si-CS provided its synergistic adsorption for Hg²⁺ and anionic dye Congo red (CR). The capture of PA-Si-CS for Hg²⁺ was rationally applied to the "enrichment"-type electrochemical probing of Hg²⁺. Relevant detection range, detection limit, interference, and probing mechanism were systematically analyzed. Compared with the experimental results of control electrodes, the electrode modified with PA-Si-CS (PA-Si-CS/GCE) showed a significantly enhanced electrochemical response to Hg²⁺, with a detection limit up to ~2.2 × 10^-8 mol/L. In addition, PA-Si-CS also exhibited the specific adsorption for CR. Systematic analyses of dye adsorption selectivity, kinetics, isothermal models, thermodynamics, and adsorption mechanism told that PA-Si-CS can be used as an efficient CR adsorbent, with a maximum adsorption capacity of ~348 mg/g.

A review of antibiotics and antibiotic resistance genes (ARGs) adsorption by biochar and modified biochar in water

Antibiotics have been used in massive quantities for human and animal medical treatment, and antibiotic resistance genes (ARGs) are of great concern worldwide. Antibiotics and ARGs are exposed to the natural environment through the discharge of medical wastewater, causing great harm to the environment and human health. Biochar has been widely used as a green and efficient adsorbent to remove pollutants. However, pristine and unmodified biochars are not considered sufficient and efficient to cope with the current serious water pollution. Therefore, researchers have chosen to improve the adsorption capacity of biochar through different modification methods. To have a better understanding of the application of modified biochar, this review summarizes the biochar modification methods and their performance, particularly, molecular imprinting and biochar aging are outlined as new modification methods, influencing factors of biochar and modified biochar in adsorption of antibiotics and ARGs and adsorption mechanisms, wherein adsorption mechanism of ARGs on biochar is found to be different than that of antibiotics. After that, the directions of biochar and modified biochar worthy of research and the issues that need attention are proposed. It can be noted that under the current dual carbon policy, biochar may have wider application prospects in future.

Removal of methylene blue dye from aqueous solution using an efficient chitosan-pectin bio-adsorbent: kinetics and isotherm studies

Wastewater contains organic compounds, including dyes, which have potential risks to the environment. Hence, these compound needs to be eliminated from the aqueous solution. In the present study, chitosan-pectin composite (Cs-Pc) was used as an adsorbent to remove methylene blue dye (MB) from synthetic wastewater. To evaluate the parameters affecting adsorption, including the initial MB concentration, solution pH, contact time, and Cs-Pc dose, batch experiments were carried out. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), and pH point of zero charges (pH pzc) were applied for characterizations of Cs-Pc. The optimum conditions were obtained with an initial MB concentration of 50 mg L^-1: solution pH ~ 11, Cs-Pc dose: 1.5 g L^-1 and 180 min contact time, which caused 97.77% of MB removal. In addition, the removal efficiency of MB was more influenced by pH than by sorbate dose. Also, Cs-Pc had a higher ability to remove MB than chitosan and pectin, probably due to its highly porous structure and rough surfaces that provides active sites and facilitate MB adsorption. The maximum removal efficiency and the adsorption capacity of MB onto Cs-Pc at 500 mg L^-1 concentration under optimum conditions were 98.67% and 328.02 mg g^-1, respectively. The adsorption kinetics and isotherms were best described by pseudo-second-order and Freundlich equation, respectively. After four times of recycling, the removal efficiency of MB was above 96%. Electrostatic and pi-pi interactions are the main mechanisms for the removal of MB onto the adsorbent. So the application of Cs-Pc is promising for MB removal from polluted solutions not only due to its strong adsorbing capability but also due to its excellent ability to reuse.

High-efficiency adsorption removal of CR and MG dyes using AlOOH fibers embedded with porous CoFe2O4 nanoparticles

Owing to the toxicity and difficulty in degradation, how to the effective separation for the residual dyes in the aqueous solution is still an issue with great challenge in the area of environmental protection. Now, to high-efficiency removal of organic dyes from the aqueous solution, we design a unique AlOOH/CoFe₂O₄ adsorbent with porous CoFe₂O₄ nanoparticles embedded on the AlOOH fibers using a simple hydrothermal technique and calcination process. The structural properties and surface characteristics of the AlOOH/CoFe₂O₄ composites are detailedly analyzed by XRD, FTIR, XPS, TEM and SEM. Here, the high S_BET and specific porous structure are beneficial to improve the adsorption performance of AlOOH/CoFe₂O₄ adsorbents. Especially, when the molar ratio of AlOOH to CoFe₂O₄ in the AlOOH/CoFe₂O₄ fibers is 1:1, an optimal performance on adsorbing anionic Congo red (CR) and cationic methyl green (MG) dyes can be obtained at pH = 6.29, where the corresponding maximum adsorption capacities reach up to 565.0 and 423.7 mg g^-1, respectively. Factors leading to the change in the ability of adsorbing CR and MG dyes are systematically discussed, including contact time, temperature, initial concentrations, and pH values of the solutions. Meanwhile, the uptake of CR and MG dyes can best conform to Langmuir isotherm model and pseudo-second-order adsorption kinetics. The thermodynamic analysis verifies that the dye adsorption process is spontaneous and endothermic. Moreover, from the point view of practical application, the good reusability further makes the as-synthesized magnetic AlOOH/CoFe₂O₄ composite be a perfect adsorbent with efficiently removing both anionic and cationic dyes from aqueous solutions.

Regulating the exposed crystal facets of α-Fe2O3 to promote Fe2O3-modified biochar performance in heavy metals adsorption

α-Fe₂O₃ modified biochar (Fe₂O₃/BC) was prepared to remove Cu(II), Pb(II) and As(V). By adjusting the calcination temperature, the morphology and exposed crystal facets of α-Fe₂O₃ on the biochar were changed which further affected the adsorption performance. The kinetics and isotherms were investigated systematically to reveal adsorption effect of the adsorbent on Cu(II), Pb(II) and As(V). The results indicated that chemisorption process was the dominant adsorption mechanism. Fe₂O₃/BC-350 exhibited superior adsorption capacity for Cu(II) (258.22 mg/g) and Pb(II) (390.60 mg/g), and Fe₂O₃/BC-250 showed relatively good adsorption capacity for As(V) (5.78 mg/g). By adsorption mechanism analysis, electrostatic adsorption, ion exchange, precipitation and complexation were coexisted in the process of removing metal ions by Fe₂O₃/BC. The repeatability test and the effect of ion strength exhibited the strong stability of Fe₂O₃/BC. Meanwhile, density functional theory (DFT) calculations manifested that the (202) facet of α-Fe₂O₃ on Fe₂O₃/BC-350 possessed the lowest adsorption energies of Cu(II) and Pb(II). While for As(V), it was the (104) facet of α-Fe₂O₃ on Fe₂O₃/BC-250 that exhibited the lowest adsorption energy. DFT results revealed that different Fe₂O₃/BC had different adsorption affinities to various heavy metals. In general, this work not only prepared a promising adsorbent via a simple procedure, but also served as a reference for researchers in designing absorbents with specific active facet for efficient heavy metals remediation.

Ultrahigh sorption of sulfamethoxazole by potassium hydroxide-modified biochars derived from bean-worm skin waste

Food processing of bean worm generates copious amount of skin as solid waste posing a serious environmental concern. The present study utilized bean worm skin (BWS) waste to produce KOH-modified biochars (KBWS-BCs) for the removal of sulfamethoxazole (SMX) from aqueous solution for the first time. Characterization of KBWS-BCs was systematically investigated via multiple instrumental analysis techniques. The sorption performance of KBWS-BCs as a function of solution pH, reaction time, initial SMX concentration, and reaction temperature was investigated using batch experiments. The classic kinetics and isotherm models were employed to fit the sorption data. KBWS-BCs exhibited large surface areas (3331-4742 m² g^-1) and ultrahigh sorption performance for SMX (maximum adsorption capacities of 909-2000 mg g^-1), which were comparable to those of other modified biochars and even those of well-designed materials. Thermodynamic study indicated that the sorption of SMX on KBWS-BCs was a spontaneous (△G° < 0) and exothermic (△H° < 0) process. Mechanism analysis showed that both chemisorption and physisorption were responsible for the adsorption of SMX by KBWS-BCs. Overall, recycling BWS for preparation of high-performance biochars can be a "win-win" strategy for both disposal of BWS and removal of SMX from wastewater.

Biochar Obtained from Caryocar brasiliense Endocarp for Removal of Dyes from the Aqueous Medium

Given the increase in environmental pollution, especially of water, the emergence of studies that seek to develop strategies to mitigate/treat such effects have gained prominence in the world scientific community. Among the numerous adsorption processes, those made from biochar production stand out. This study analyzed the adsorption properties of the blue methylene model dye in the aqueous solution of biochar and activated biochar developed from pequi (Caryocar brasiliense) endocarp. The biochar was characterized, before and after adsorption, by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TG). The surface load of the materials was performed by the point of zero charge (pH_PZC) method. The study also included analyses of contact time parameters and adsorbed concentration in the adsorption process. Morphological analysis showed that a more significant and profound number of fissures and pores appeared in the activated biochar compared to the biochar. Residual mass analysis evidenced that biochar lost about 15% more mass than the activated biochar, indicating that activation occurred satisfactorily. The adsorption process was well adjusted by pseudo-second-order kinetics and Langmuir's isothermal model. The activated biochar achieved an excellent adsorption capacity of 476.19 mg.g^-1, thus demonstrating to be a sound system for removing dyes from an aqueous medium.

Adsorption Characteristics and Mechanism of Methylene Blue in Water by NaOH-Modified Areca Residue Biochar

To solve the water pollution problem caused by methylene blue (MB), areca residue biochar (ARB) was prepared by pyrolysis at 600 °C, and modified areca residue biochar (M-ARB) was obtained by modifying ARB with 1.5 mol/L NaOH, and they were utilized to adsorb and eliminate MB from water. The structural characteristics of ARB and M-ARB were examined, and the main influencing factors and adsorption mechanism of MB adsorption process were investigated. The outcomes demonstrated an increase in M-ARB’s specific surface area and total pore volume of 66.67% and 79.61%, respectively, compared with ARB, and the pore structure was more abundant, and the content of oxygen element was also significantly increased. When the reaction temperature was 25 °C, starting pH of the mixture was 10, the initial MB concentration was 50 mg/L, the ARB and M-ARB dosages were 0.07 g/L and 0.04 g/L, respectively, the adsorption equilibrium was achieved at about 210 min, and the elimination rate for MB exceeded 94%. The adsorption behaviors of ARB and M-ARB on MB were more in line with the Langmuir isotherm model (R2 > 0.95) and the quasi-secondary kinetic model (R2 > 0.97), which was characterized by single-molecule layer chemisorption. The highest amount of MB that may theoretically be absorbed by M-ARB in water ranging from 136.81 to 152.72 mg/g was 74.99–76.59% higher than that of ARB. The adsorption process was a spontaneous heat absorption reaction driven by entropy increase, and the adsorption mechanism mainly involved electrostatic gravitational force, pore filling, hydrogen bonding, and π–π bonding, which was a complex process containing multiple mechanisms of action. NaOH modification can make the ARB have more perfect surface properties and more functional group structures that can participate in the adsorption reaction, which can be used as an advantageous adsorption material for MB removal in water.

Biochar application for remediation of organic toxic pollutants in contaminated soils; An update

Bioremediation of organic contaminants has become a major environmental concern in the last few years, due to its bio-resistance and potential to accumulate in the environment. The use of diverse technologies, involving chemical and physical principles, and passive uptake utilizing sorption using ecofriendly substrates have drawn a lot of interest. Biochar has got attention mainly due to its simplicity of manufacturing, treatment, and disposal, as it is a less expensive and more efficient material, and has a lot of potential for the remediation of organic contaminants. This review highlighted the adverse impact of persistent organic pollutants on the environment and soil biota. The utilization of biochar to remediate soil and contaminated compounds i.e., pesticides, polycyclic aromatic hydrocarbons, antibiotics, and organic dyes has also been discussed. The soil application of biochar has a significant impact on the biodegradation, leaching, and sorption/desorption of organic contaminants. The sorption/desorption of organic contaminants is influenced by chemical composition and structure, porosity, surface area, pH, and elemental ratios, and surface functional groups of biochar. All the above biochar characteristics depend on the type of feedstock and pyrolysis conditions. However, the concentration and nature of organic pollutants significantly alters the sorption capability of biochar. Therefore, the physicochemical properties of biochar and soils/wastewater, and the nature of organic contaminants, should be evaluated before biochar application to soil and wastewater. Future initiatives, however, are needed to develop biochars with better adsorption capacity, and long-term sustainability for use in the xenobiotic/organic contaminant remediation strategy.

Activated carbon prepared by co-pyrolysis of waste tobacco straw and waste LDPE mulch film: characterization and application for methylene blue removal

Efficient and inexpensive sorbents play a key role in removing organic pollutants from water bodies. In this study, a series of high surface area activated carbons (ACs) with excellent adsorption performance was prepared by co-pyrolysis of the waste tobacco straw and the waste low-density polyethylene (LDPE) mulch film. Using the maximum adsorption capacity of methylene blue (MB) as an indicator, the variables such as LDPE content, K₂CO₃ to raw material ratio, activation time, and activation temperature were optimized. The optimal synthesis conditions were as follows: LDPE content of 40%, K₂CO₃/raw material ratio of 1 : 2, activation temperature of 900 °C, and activation time of 100 min. The maximum adsorption capacity of MB was up to 849.91 mg g^-1. The results of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and BET showed that the moderate addition of LDPE was beneficial to the pyrolysis of the waste tobacco straw, bringing about the enrichment of surface groups (-OH, -COOH) and increasing its specific surface area and pore volume (up to 1566.7 m² g^-1 and 0.996 cm³ g^-1, respectively). The equilibrium data of MB adsorption by the composite activated carbon (PAC) was consistent with the Langmuir isotherm, while the adsorption kinetics were better described by a pseudo-second-order kinetic model. This work reveals the feasibility of LDPE mulch film and waste tobacco straw as potential and inexpensive precursors for preparing high surface area AC adsorbents.

Prosopis juliflora Seed Waste as Biochar for the Removal of Blue Methylene: A Thermodynamic and Kinetic Study

In this work, we studied the methylene blue (MB) dye adsorption capacity on biochar derived from residues of Prosopis juliflora seed waste, a species found in the region of the tropical dry forest of Piojó in the Department of Atlántico, Colombia. The materials were obtained by pyrolysis at temperatures of 300, 500, and 700 °C. Biochar was characterized using Fourier transform infrared (FTIR), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX), TGA, and Brunauer-Emmett-Teller (BET) techniques. The three biochar samples presented a macroporous, rough structure with pore size between 6 and 28 μm. The largest pore surface area observed was 1.28 m²/g for pyrolyzed biochar produced at 500 °C, larger than that of biochar produced at 700 °C, which was 0.83 m²/g. The adsorption results show that the maximum percentage of MB removal was 69%. According to SEM results, the material's pore sizes varied on average from 6 to 28 μm. We modeled MB adsorption on biomass through three different isotherm models. The Freundlich model was the best-fitting model for the removal of MB (K _F = 1.447; 1/n = 0.352). The kinetic results showed that the pseudo-second-order model was the best-fitting model for the sorption process (q _e = 2.94 mg/g; k ₂ = 0.087 g/(mg/min^-1)). Furthermore, the recycling test showed that the biochar did not change its adsorption capacity significantly. Finally, under the experimental conditions, the thermodynamic parameters indicated that the removal of MB using biochar was an endothermic and spontaneous process; all ΔG° values ranged from -2.14 to -0.95 kJ/mol; ΔH° was 23.54 kJ/mol and ΔS° was 79.5 J/mol.

Removal of ofloxacin from water by natural ilmenite-biochar composite: A study on the synergistic adsorption mechanism of multiple effects

The preparation cost is one of the major constraints for adsorbent applied to practical situations. Here, a novel, economical and eco-friendly ilmenite biochar composite (ILM-BC) was successfully prepared by co-cracking of natural ilmenite and corn stover for the removal ofloxacin from water. The adsorption experiments indicated that the removal ofloxacin by ILM-BC was chemisorption and belonged to a spontaneous and entropy-increasing heat absorption process. Among composites, ILM-BC5 had superior adsorption capacity and stability, with a removal rate 1.6 times higher than that of biochar, and it could remove more than 90% ofloxacin in the pH range of 2-10. Multiple characterization results indicated that the adsorption of ILM-BC was the result of the synergistic effect of pore filling, hydrogen bonding, and π-π interactions. The introduction of ilmenite promoted hydrogen bonding formation and π-π interactions by enriching -OH and -COO on the surface of ILM-BC, which could enhance the adsorption capacity of ILM-BC.

Sustainable conversion of textile industry cotton waste into P-dopped biochar for removal of dyes from textile effluent and valorisation of spent biochar into soil conditioner towards circular economy

Effective immobilization of industrial waste into biochar development could be one of the most promising technologies for solid waste management to achieve circular economy. In this study, post-industrial cotton textile waste (PICTW), a cellulose rich industrial waste, was subjected to slow pyrolysis to develop a surface engineered biochar through phosphoric acid impregnation. Biochar produced at 500 °C designated as PICTWB500 showed a maximum methylene blue number (240 mg g^-1) with remarkable specific surface area of 1498 m² g^-1. FESEM, FTIR, XRD and Raman spectra analysis were performed to investigate the surface texture and functionalities developed in the biochar. Adsorption efficiency of the biochar was assessed using drimarene red, blue, violet, and black dyes as model dye pollutants in batch mode at different biochar dose, pH and contact time. The maximum monolayer adsorption capacity was obtained in the range 285-325 mg g^-1 for different dyes, determined from Langmuir adsorption model. The kinetic behaviour was more favourable with the pseudo second-order model. The recycling ability of PICTWB500 was proven to be effective up to 6th cycle without compromising its adsorption efficiency significantly. This study demonstrated an excellent adsorption capability of the biochar in dye laden real textile effluent and recycling of spent biochar as a precursor of bio compost. Hence, this study established a dual win strategy for waste utilization in textile industry using a closed loop approach with substantial techno-economic feasibility that may have potential applications.

Removal of Dye (Methylene Blue) from Wastewater Using Bio-Char Derived from Agricultural Residues in Palestine: Performance and Isotherm Analysis

The main aim of this study was to perform a parametric study for treating a model dye containing wastewater (i.e., methylene blue, MB) using locally available biomass wastes in Palestine as the adsorbent. Eight different types of biomasses were investigated in batch adsorption tests, including coffee grains, almond shells, pistachio shells, date pits, jute sticks, sunflower shells, peanut shells, and grapevine sticks. The experiments were conducted on three different phases of processing for these materials: as natural adsorbents, biochar, and activated carbon. The biochar was prepared by pyrolysis, while ZnCl2 was used to chemically activate the materials for obtaining activated carbon. The influences of pH, initial MB concentration, and adsorbent dosage on the adsorption capacity and kinetics were investigated for activated carbon obtained from sunflower shells. The results indicate that the adsorption efficiency of natural adsorbents and biochar is highly dependent on the biomass type. As a natural adsorbent, peanut hulls demonstrated the maximum efficiency (>95%) for removing MB, whereas date pits showed the lowest efficiency (20%). In terms of biochar, jute sticks provide the highest removal efficiency. After activation with ZnCl2, a considerable increase in their adsorption efficiency (>95%) was obtained for most of the adsorbents, with sunflower shells being the most efficient adsorbent. The results confirm the technical feasibility of the adsorption technology to treat dye containing wastewater using locally available biomass wastes.