Adsorption Characteristics of Sulfamethoxazole and Metronidazole on Activated Carbon

Facile and green synthesis of recyclable, environmentally friendly, chemically stable, and cost-effective magnetic nanohybrid adsorbent for tetracycline adsorption

Antibiotic contamination of water sources, particularly tetracycline (TC) contamination, has emerged as one of the global issues that needs action. In this research, ZnCoFe2O4@Chitosan (Ch) as a magnetic nanohybrid adsorbent was synthesized using the microwave-assisted co-precipitation method, and their efficiency for the TC adsorption process was investigated. FESEM (Field Emission Scanning Electron Microscope), EDX (Energy Dispersive X-ray), Mapping and line Scan, XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectrometer), VSM (Vibrating Sample Magnetometer), Thermogravimetric analysis (TGA) and BET (Brunauer Emmett Teller) techniques were used to check and verify its physical and chemical properties. The removal of TC via the adsorption process from synthetic and real wastewater samples was investigated. The factors determining the TC adsorption process, comprising tetracycline concentration (5-30 mg/L), adsorbent dosage (0.7-2 g/L), contact time (2-45 min), and pH (3-11), were evaluated. The removal effectiveness for the synthetic sample and the real wastewater sample was 93 % and 80 %, respectively, under the ideal TC adsorption process parameters of pH 3, adsorbent dosage 1 g/L, TC initial concentration 5 mg/L, and contact time 30 min. According to kinetic and equilibrium studies, the adsorption of TC by ZnCoFe2O4@Ch follows pseudo-second-order kinetics and the Freundlich isotherm. Additionally, it was determined through the analysis of thermodynamic data that the process of exothermic adsorption is spontaneous and is followed by a decrease in disorder (ΔH = -15.16 kJ/mol, ΔS = -28.69 kJ/mol, and ΔG = -6.62 kJ/mol). After five cycles of recovery and regeneration, the ZnCoFe2O4@Ch magnetic nanocomposite was able to remove 65 % of the TC pollutant and had good chemical stability. The results showed that the magnetic nano-adsorbent ZnCoFe2O4@Ch is a novel magnetic nano-adsorbent with high adsorption capacity that can be utilized to eliminate pharmaceutical contaminants from aqueous solutions.

Preparation and evaluation of a coated smectite clay-based material modified with epichlorohydrin-dimethylamine for the diclofenac removal

This study reports the analysis of diclofenac removal from aqueous solution using a novel adsorbent coating with amphoteric surface. This adsorbent coating was improved using a new amphoteric ratio to increase its performance for the removal of pharmaceuticals such as diclofenac. The adsorbent coating was formulated using acrylic polymer emulsion, smectite-based clay powder and epichlorohydrin-dimethylamine to obtain a layer form via the implementation of a facile synthesis method. In a previous study, this adsorbent coating was successful to remove cationic and anionic dyes. Therefore, this research aimed to further investigate and test its application in the removal of other emerging water pollutants like pharmaceuticals. SEM, EDX, and FTIR analyses were carried out for the characterization of this novel adsorbent. The effects of adsorbent composition, diclofenac concentration, temperature, and solution pH were studied and modeled. The best conditions to improve the diclofenac adsorption was 303 K and pH 3 where the adsorption capacity was 25.59 mg/g. Adsorption isotherms and kinetics were quantified and modeled, and the corresponding adsorption mechanism was also analyzed. Diclofenac adsorption with this novel material was exothermic and spontaneous. This alternative adsorbent is promising for diclofenac removal from industrial wastewater systems.

Electrochemical detection of ornidazole in commercial milk and water samples using an electrode based on green synthesis of silver nanoparticles using cellulose separated from Phoenix dactylifera seed

The widespread use of antibiotics has contributed to the control of disease and the nutritional well-being of livestock. Antibiotics reach the environment via excretions (urine and feces) from human and domestic animals, through non proper disposal or handling of unused drugs. The present study describes a green method for the synthesis of silver nanoparticle (AgNPs) using cellulose extracted from Phoenix dactylifera seed powder via mechanical stirrer method for the electroanalytical determination of ornidazole (ODZ) in milk and water samples. The cellulose extract is used as the reducing and stabilizer agent for the synthesis of AgNPs. The obtained AgNPs were characterized by UV-Vis, SEM and EDX, presenting a spherical shape and an average size of 48.6 nm. The electrochemical sensor (AgNPs/CPE) was fabricated by dipping a carbon paste electrode (CPE) in the AgNPs colloidal solution. The sensor shows acceptable linearity with ODZ concentration in the linear range from 1.0 × 10^-5 to 1.0 × 10^-3 M with a limit of detection (LOD =3S/P) and quantification (LOQ =10S/P) of 7.58 × 10^-7 M and 2.08 × 10^-6 M respectively.

Study of the Influence of the Wastewater Matrix in the Adsorption of Three Pharmaceuticals by Powdered Activated Carbon

The use of powdered activated carbon (PAC) as an absorbent has become a promising option to upgrade wastewater treatment plants (WWTPs) that were not designed to remove pharmaceuticals. However, PAC adsorption mechanisms are not yet fully understood, especially with regard to the nature of the wastewater. In this study, we tested the adsorption of three pharmaceuticals, namely diclofenac, sulfamethoxazole and trimethoprim, onto PAC under four different water matrices: ultra-pure water, humic acid solution, effluent and mixed liquor from a real WWTP. The adsorption affinity was defined primarily by the pharmaceutical physicochemical properties (charge and hydrophobicity), with better results obtained for trimethoprim, followed by diclofenac and sulfamethoxazole. In ultra-pure water, the results show that all pharmaceuticals followed pseudo-second order kinetics, and they were limited by a boundary layer effect on the surface of the adsorbent. Depending on the water matrix and compound, the PAC capacity and the adsorption process varied accordingly. The higher adsorption capacity was observed for diclofenac and sulfamethoxazole in humic acid solution (Langmuir isotherm, R² > 0.98), whereas better results were obtained for trimethoprim in the WWTP effluent. Adsorption in mixed liquor (Freundlich isotherm, R² > 0.94) was limited, presumably due to its complex nature and the presence of suspended solids.

Adsorption of Toxic Tetracycline, Thiamphenicol and Sulfamethoxazole by a Granular Activated Carbon (GAC) under Different Conditions

Activated carbon can be applied to the treatment of wastewater loading with different types of pollutants. In this paper, a kind of activated carbon in granular form (GAC) was utilized to eliminate antibiotics from an aqueous solution, in which Tetracycline (TC), Thiamphenicol (THI), and Sulfamethoxazole (SMZ) were selected as the testing pollutants. The specific surface area, total pore volume, and micropore volume of GAC were 1059.011 m²/g, 0.625 cm³/g, and 0.488 cm³/g, respectively. The sorption capacity of GAC towards TC, THI, and SMZ was evaluated based on the adsorption kinetics and isotherm. It was found that the pseudo-second-order kinetic model described the sorption of TC, THI, and SMZ on GAC better than the pseudo-first-order kinetic model. According to the Langmuir isotherm model, the maximum adsorption capacity of GAC towards TC, THI, and SMZ was calculated to be 17.02, 30.40, and 26.77 mg/g, respectively. Thermodynamic parameters of ΔG⁰, ΔS⁰, and ΔH⁰ were obtained, indicating that all the sorptions were spontaneous and exothermic in nature. These results provided a knowledge base on using activated carbon to remove TC, THI, and SMZ from water.

Shrimp waste-derived porous carbon adsorbent: Performance, mechanism, and application of machine learning

Aquaculture generates significant amount of processing wastes (more than 500 million pounds annually in the United States), the bulk of which ends up in the environment or is used in animal feed. Proper utilization of shrimp waste can increase their economic value and divert them from landfills. In this study, shrimp waste was converted to a porous carbon (named SPC) via direct pyrolysis and activation. SPC was characterized, and its performance for adsorbing ciprofloxacin from simulated water, natural waters, and wastewater was benchmarked against a commercial powdered activated carbon (PAC). The surface area of SPC (2262 m²/g) exceeded that of PAC (984 m²/g) due to abundance of micropores and mesopores. The adsorption of ciprofloxacin by SPC was thermodynamically spontaneous (ΔG = -19 kJ/mol) and fast (k₁ = 1.05/min) at 25 °C. The capacity of SPC for ciprofloxacin (442 mg/g) was higher than that of PAC (181 mg/g). SPC also efficiently and simultaneously removed low concentrations (200 µg/L) of ciprofloxacin, long-chain per- and polyfluoroalkyl substances (PFAS), and Cu ions from water. An artificial neural network function was derived to predict ciprofloxacin adsorption and identify the relative contribution of each input parameter. This study demonstrates a sustainable and commercially viable pathway to reuse shrimp processing wastes.

New nanostructured activated biochar for effective removal of antibiotic ciprofloxacin from wastewater: Adsorption dynamics and mechanisms

Developing green inexpensive and effective adsorbents is critically needed for elimination of antibiotics from contaminated water. The current study assessed the nanostructured activated biochar (nPPAB) derived from pomegranate peels (PP) as a promising sorbent for efficient removal of the antibiotic ciprofloxacin (CIP). The results affirm that the second order and Langmuir models fit well to adsorption kinetics and equilibrium data respectively. The nPPAB adsorption capacity of Langmuir (q_max) for CIP was 142.86 mg g^-1 which is 26.85 times greater than that of bulk PP. Hydrogen bonding, π-π interaction, hydrophobic and electrostatic interactions are the dominant mechanisms of CIP adsorption by nPPAB. The efficiency of nPPAB for CIP removal from real wastewater using batch and packed-bed reactor were 89.94 and 84.74% respectively. This study clearly demonstrated the substantial capacity of nPPAB as an ecofriendly, feasible, and in-expensive adsorbent for successful elimination of CIP from wastewater.

Biophysical and molecular modeling evidences for the binding of sulfa molecules with hemoglobin

The molecular mechanism of the heme protein, hemoglobin (Hb) interaction with sulfa molecule, sulfadiazine (SDZ) has been investigated through spectroscopic, neutron scattering and molecular modeling techniques. Absorption and emission spectroscopic studies showed that SDZ molecules were bound to Hb protein, non-cooperatively. The binding affinityof SDZ-Hb complex at standard experimental condition was evaluated to be around (4.2 ± 0.07) ×10⁴, M^-1with 1:1 stoichiometry. Drug induced structural perturbation of the 3 D protein moiety was confirmed through circular dichroism (CD), synchronous fluorescence and small angle neutron scattering methods. From the temperature dependent spectrofluorometric studies, the negative standard molar Gibbs energy change suggested the spontaneity of the reaction. The negative enthalpy and positive entropy change(s) indicated towards the involvement of both electrostatic and hydrophobic forces during the association process. Salt dependent fluorescence study revealed major contributions from non-poly-electrolytic forces. Molecular modeling studies determined the probable binding sites, types of interaction involved and the conformational alteration of the compactness of the Hb structure upon interaction with SDZ molecule. Overall, the study provides detailed insights into the binding mechanism of SDZ antibiotics to Hb protein.Communicated by Ramaswamy H. Sarma.

Kinetic and isotherm insights of Diclofenac removal by sludge derived hydrochar

Recently, hydrothermal carbonization emerges as the most viable option for the management of solid waste with high moisture content. Sludge derived hydrochar is used as an adsorbent for emerging contaminants or micro-pollutants in the domain of sustainability. Current study demonstrates the KOH activation of hydrochar produced from paper board mill sludge and evaluates its removal potential of a Non-steroidal anti-inflammatory drug, Diclofenac from aqueous solution. The activated hydrochars exhibited porous, spherical micro-structures with higher fraction of oxygenated functional groups paving way for the efficient adsorption of Diclofenac. The effect of initial Diclofenac concentration and contact time was ascertained using adsorption kinetics and isotherms. The adsorption kinetics exhibited second-order reaction for all adsorbents indicating higher coefficient of determination (R² > 0.9). The Diclofenac adsorption on hydrochars followed Langmuir isotherm model with the post-activated hydrochar recording a highest adsorption capacity of 37.23 mg g⁻¹ in 40 mg L⁻¹ initial Diclofenac concentration at 15 h equilibrium time.

Quick removal of metronidazole from aqueous solutions using metal–organic frameworks

Two MOFs were assembled, characterized and investigated in detail as efficient adsorbents for removal of the metronidazole antibiotic. Adsorption isotherms and kinetic features were also studied.

Adsorption and detoxification of pharmaceutical compounds from wastewater using nanomaterials: A review on mechanism, kinetics, valorization and circular economy

Antibiotics overuse, inappropriate conduct, and discharge have led to adverse effects on various ecosystems. The occurrence of antibiotics in surface and drinking water is a matter of global concern. It is responsible for multiple disorders, including disruption of endocrine hormones and high chronic toxicity. The hospitals, pharmaceutical industries, households, cattle farms, and aquaculture are the primary discharging sources of antibiotics into the environment. This review provides complete detail on applying different nanomaterials or nanoparticles for the efficient removal of antibiotics from the diverse ecosystem with a broader perspective. Efforts have been made to focus on the degradation pathways and mechanism of antibiotic degradation using nanomaterials. More light has been shed on applying nanostructures in photocatalysis, which would be an economical and efficient solution. The nanoscale material or nanoparticles have incredible potential for mineralizing pharmaceutical compounds in aqueous solutions at low cost, easy handling characteristics, and high efficacy. Furthermore, nanoparticles can absorb the pharmaceutical by-products and wastes at a minimum cost as they can be easily recycled. With the increasing number of research in this direction, the valorization of pharmaceutical wastes and by-products will continue to expand as we progress from old conventional approaches towards nanotechnology. The utilization of nanomaterials in pharmaceutical wastewater remediation is discussed with a major focus on valorization, energy generation, and minimization and its role in the circular economy creating sustainable development.

Biochar-Supported TiO2-Based Nanocomposites for the Photocatalytic Degradation of Sulfamethoxazole in Water-A Review

Sulfamethoxazole (SMX) is a frequently used antibiotic for the treatment of urinary tract, respiratory, and intestinal infections and as a supplement in livestock or fishery farming to boost production. The release of SMX into the environment can lead to the development of antibiotic resistance among the microbial community, which can lead to frequent clinical infections. SMX removal from water is usually done through advanced treatment processes, such as adsorption, photocatalytic oxidation, and biodegradation. Among them, the advanced oxidation process using TiO2 and its composites is being widely used. TiO2 is a widely used photocatalyst; however, it has certain limitations, such as low visible light response and quick recombination of e-/h+ pairs. Integrating the biochar with TiO2 nanoparticles can overcome such limitations. The biochar-supported TiO2 composites showed a significant increase in the photocatalytic activities in the UV-visible range, which resulted in a substantial increase in the degradation of SMX in water. The present review has critically reviewed the methods of biochar TiO2 composite synthesis, the effect of biochar integration with the TiO2 on its physicochemical properties, and the chemical pathways through which the biochar/TiO2 composite degrades the SMX in water or aqueous solution. The degradation of SMX using photocatalysis can be considered a useful model, and the research studies presented in this review will allow extending this area of research on other types of similar pharmaceuticals or pollutants in general in the future.

Cyclodextrin polymers and salts: An Eco-Friendly combination to modulate the removal of sulfamethoxazole from water and its release

This study is aimed to validate water-insoluble cyclodextrin-epichlorohydrin polymer (β-EPI) use to remove, by adsorption, sulfamethoxazole (SMX) from water and then release it via an environmentally friendly treatment so that the adsorbent can be recycled according to one of the objectives of the European Project Life "Clean up" (LIFE 16 ENV/ES/000169). SMX adsorption experiments on β-EPI polymer in-batch were performed, varying different experimental parameters of the process, such as contact time, pH values, and so on. The adsorption process, exothermic and driven by enthalpy, occurs both through the formation of inclusion and association complexes, involves mainly hydrophobic and hydrogen bonds, has a rate-controlling step depending on both pollutant concentration and adsorbent dose and can be described by the Freundlich and Dubinin-Radushkevich models which confirm the polymer surface heterogeneity and the physical nature of the adsorption. The presence of salts gives rise to a general decrease in the SMX sorption, mainly in the case of bromide, which was used to promote the SMX desorption and regenerate the adsorbent. The overall results indicate that β-EPI polymer is not only capable of removing SMX by adsorption with short contact times and a q_max = 10 mg/g but it is also easily regenerated using a 0.5 M solution of sodium bromide without any loss in the adsorption performance and with obvious economic and environmental advantages. The polymer as synthesized, with SMX adsorbed and regenerated was characterized by FT-IR, SEM and DSC.

Nickel Removal from Aqueous Solution Using Chemically Treated Mahogany Sawdust as Biosorbent

Sawdust is a waste material, which is generally produced during making furniture and other necessary wood products. With a view to utilizing this waste material, a biosorbent was prepared from mahogany (Swietenia macrophylla) sawdust through simple chemical treatment and was used to remove nickel ion (Ni2+) from an aqueous solution. The adsorbent material was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. The effects of biosorbent dosage (2∼18 g/L), pH of the tested solution (4∼10.5), contact time (up to 360 min), and temperature (298∼318 K) were studied in batchwise experiments. The maximum adsorption capacity of the treated sawdust was determined to be 13.42 mg/g at an optimum condition (sorbent dose of 15 g/L, pH of 9, and temperature of 298 K). The experimental data extrapolation revealed that the adsorption process fitted the Langmuir isotherm model and the kinetics was a pseudo-second-order kinetic model. The obtained thermodynamic parameters indicated that the adsorption reaction was spontaneous, endothermic, and random in nature. The study revealed that sawdust biosorbent has potential adsorption efficiency for nickel ion removal from an aqueous solution.

Phytoextraction of ciprofloxacin and sulfamethoxaxole by cattail and switchgrass

Cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.) can effectively remove inorganic contaminants from soils and biosolids, but their role in the attenuation of organic contaminants, such as antimicrobials, is currently poorly understood. Uptake by plants is one of several mechanisms by which plant-assisted attenuation of antimicrobials can be achieved. The objectives of this growth room study were to evaluate the plant uptake of ciprofloxacin (CIP) and sulfamethoxazole (SMX) and examine their partitioning between plant roots and aboveground biomass (AGB). Plant uptake of the two ¹⁴C labeled antimicrobials was studied at two environmentally relevant concentrations (5 and 10 μg L^-1). Plants were destructively sampled every 3-4 d during the 21-d growth period. Accumulation of CIP and SMX in both plant species was greater in the roots than in the AGB. The percentage uptake values of the two antimicrobials were significantly greater for cattail (34% for CIP, 20% for SMX) than for switchgrass (10% for both CIP and SMX). Translocation factors of the two antimicrobials were <1 for both plants, indicating slow movement of the antimicrobials from the roots to the shoots. For cattail roots, the BCF for CIP (1.58 L g^-1) was significantly greater than that for SMX (0.8 L g^-1). By comparison, BCFs for switchgrass roots did not differ significantly between CIP (0.88 L g^-1) and SMX (1.13 L g^-1). These results indicate greater potential for cattail to phytoextract CIP and SMX and significantly contribute to the attenuation of these antimicrobials in systems designed for the phytoremediation of contaminated wastewater.

Antibacterial Agents Adsorbed on Active Carbon: A New Approach for S. aureus and E. coli Pathogen Elimination

Antibiotic overuse and mass production have led to a global problem with the treatment of antibacterial infections. Thus, any possibility to limit the number of antibacterial drugs used will contribute to a decrease in the development of pathogenic bacterial resistance. In this study, the enhanced bacterial growth reduction of pharmaceutical activated carbon (PAC) material with adsorbed antimicrobial agents compared to the activity of pure antibacterial drugs was investigated. Sulfamethoxazole (SMZ) at a concentration of 1.1 mg/mL retained the growth of S. aureus and E. coli at 20.5% and 26.5%, respectively, whereas SMZ adsorbed on PAC increased the reduction of the tested bacteria in the range of 47-72%. The use of PAC with adsorbed gentamycin (G) over 24 h improved the effectiveness of E. coli growth reduction by 50% compared to the application of pure antibiotic (3.6 µg/mL). The increased reduction of S. aureus growth by 6% using G with PAC for a 24-h incubation time compared to the use of pure antibiotics at a concentration of 3.6 µg/mL was observed. The results provide proof-of-principle that the new approach of activated carbon with adsorbed antimicrobial agents could yield an attractive background with potential as a new starting material for S. aureus and E. coli pathogen elimination, e.g., in wound-healing treatment in the future.

Influence of metronidazole on activated sludge activity

Metronidazole is potentially carcinogenic to humans and it has been detected in wastewaters. The Wastewater Treatment Plants using biological processes have been highly impacted by the emergent compounds of recalcitrant type, and the knowledge about that issue is quite relevant. Therefore, this paper was focused on how metronidazole influences the kinetics and metabolic behaviour of nitrification and heterotrophic activity on activated sludge in batch cultures. Eight concentrations of metronidazole in the range of 5-100 mg/L were evaluated, in the presence of 2109 ± 129 mg VSS/L. The increment of initial metronidazole concentration caused a decline on COD and ammonium removal efficiencies, nitrate production yields, as well as in the substrate-specific consumption rates. Metronidazole (MDZ) had a greater impact on heterotrophic activity than nitrifying activity; also, it had a greater inhibitory effect on nitrite oxidation than ammonium oxidation. The activated sludge was not able to biotransform metronidazole; however, the azole compound significantly affected the physiology of it. The inhibition of ammonium oxidation was non-competitive (q_max= 120 mg NH₄⁺-N consumed/gVSS-d, and K_i = 41.5 mg MDZ/L) and the initial metronidazole concentration that inhibited 50% of nitrifying activity (IC₅₀) was 43 mg MDZ/L.

Adsorption of 4-chlorophenol by magnetized activated carbon from pomegranate husk using dual stage chemical activation

Separation under the influence of magnetic field has been widely explored to tackle environmental issues related to centrifuging and filtration. In this work, activated carbon produced from pomegranate husk (PHAC) using dual stage chemical activation was magnetized with iron salts and used for adsorption of 4-chlorophenol (4CP) from the synthetic wastewater. Adsorption experiments were conducted in batch mode to determine the removal efficiency of magnetized activated carbon pomegranate husk (MPHAC) as a function of initial 4CP concentration, solution pH, MPHAC dose, contact time, ionic strength, and temperature. The rough surface of MPHAC containing pores on the surface had a total pore volume of 0.623 cm³/g with a surface area of 1168 m²/g. The 4CP adsorption was highly dependent on ionic strength, solution pH, and temperature; the equilibrium was reached in 60 min of contact time. Kinetic models and equilibrium isotherms were employed to assess the fitness of adsorption data; results were fitted best with the Liu model giving maximum adsorption capacities of 446.89 ± 20.75 and 183.64 ± 17.85 mg/g for 1 and 2 g/L of MPHAC, respectively. For the investigation of the adsorption kinetics, Avrami fractionary-order model showed the best fit of the experimental data compared to other kinetic models.

Enhanced adsorptive removal of sulfamethoxazole from water using biochar derived from hydrothermal carbonization of sugarcane bagasse

This research work primarily focussed on the production of biochar from sugarcane bagasse through HTC followed by NaOH activation at inert atmosphere for removing SMX from water. The biochar was characterized for structural morphology and presence of functional groups. XRD and FTIR analysis confirmed that presence of aromatized graphitic structure accumulated with oxygenated functional groups are responsible for the elimination of SMX. SEM analysis portrayed the sphere-shaped structure of biochar with hydrophobic groups interior and hydrophilic groups exterior. BET isotherm revealed the active surface area equal to 1099 m²/g with high coverage of mesopores structure. P_zpc of adsorbent is evaluated to 6.5 stating that effective removal of SMX depends on ionization effects induced due to reaction medium. Kinetics study revealed the sorption of SMX followed chemical interaction pertaining to Elovich model. Isotherm studies revealed that Freundlich model fitted well stating heterogeneous mode of interaction. Immobilization of SMX on surface of ABC is due to charge assisted hydrogen bonding and π-π interaction with graphitized carbon, showing maximum sorption capacity of 400 mg/g through spontaneous reaction. The results suggested that HTC derived biochar had great adsorption affinity with respect to pH towards SMX and could be employed as an effective sorbent in cleaning water contaminants.

Assessment of sulfamethoxazole removal by nanoscale zerovalent iron

Removal of pharmaceutical compounds, such as sulfamethoxazole (SMX) from the aquatic environments, is critical in order to mitigate their adverse environmental and human health effects. In this study, the effectiveness of nanoscale zerovalent iron (nZVI) particles for the removal of SMX was investigated under varying conditions of initial solution pH (3, 5, 7 and 11) and nZVI to SMX mass ratios (1:1, 5:1, 10:1, 13:1, 25:1). Batch kinetic studies, which were well represented using both pseudo-first-order and pseudo-second-order kinetic models (R² > 0.98), showed that both solution pH and mass ratios strongly influenced SMX removal. At a fixed mass ratio of 10:1, removal efficiencies were higher in acidic conditions (83% to 91%) compared to neutral (29%) and alkaline (6%) conditions. A similar trend was observed for removal rates and removal amounts. For mass ratios between 1:1 and 10:1, an optimum pH existed (pH 5) wherein highest removal efficiencies were attained. Increasing the mass ratio above 10:1 resulted in virtually complete removal efficiencies at pH 3 and 5, and 70% at pH 7. Analysis of SMX speciation and zeta potential of nZVI particles provided insights into the role of pH on the efficiencies, rates and extents of SMX removal. Total organic carbon analysis and mass spectrometry measurements of SMX solution before and after exposure to nZVI particles suggested the transformation of SMX via redox reactions, which are likely the dominant process compared to adsorption. Five transformation products were observed at m/z 156 (TP1), 192 (TP2), 256 (TP3), 294 (TP4) and 296 (TP5). TP1, TP2 and TP3 were further identified using ion fragment analysis. Overall, results from this study indicate a strong potential for SMX removal by nZVI particles, and could be useful towards identifying reaction conditions for optimum SMX transformation.

Coexistence of polyethylene microplastics and biochar increases ammonium sorption in an aqueous solution

Biochar is used to remove ammonium (NH₄⁺) from wastewater, where microplastics are emerging pollutants. However, whether microplastics can adsorb NH₄⁺ or how they will affect the sorption of NH₄⁺ by biochars have not been studied. Here, batch sorption kinetics and isotherm experiments were conducted to elucidate the sorption of NH₄⁺ on a manure biochar (MBC), a straw biochar (SBC), a wood sawdust biochar (WBC), a polyethylene microplastic (PE), and their combination. The results showed that PE had a smaller sorption capacity (Q_max = 3.29 mg g^-1) but a faster adsorption rate (k_s = 0.08 g (mg min)^-1) for NH₄⁺ than biochars (Q_max = 5.67 ~ 20.54 mg g^-1; k_s = 0.02 ~ 0.04 g (mg min)^-1). When PE and biochars coexisted in an aqueous solution, the NH₄⁺ sorption capacity was increased by 17.0% in PE+SBC, 7.1% in PE+MBC, and 8.6% in PE+WBC, which likely due to the deprotonation of functional groups and the decreases in small molecular-size dissolved organic carbon. We conclude that microplastics can adsorb NH₄⁺; moreover, they can enhance the NH₄⁺ sorption capacity of biochars. Therefore, when biochar is used for NH₄⁺ removal from wastewater, the interaction of biochar and microplastics needs to be considered.

Optimizing microwave-assisted production of waste-based activated carbons for the removal of antibiotics from water

This work aimed at the microwave-assisted production of activated carbon (AC) from primary paper mill sludge (PS) for the adsorption of antibiotics from water. Production conditions, namely pyrolysis temperature, pyrolysis time and activating agent (KOH):PS ratio, were optimized as a function of product yield, specific surface area (S_BET), total organic carbon (TOC) content and adsorptive removal percentage of two target antibiotics (amoxicillin (AMX) and sulfamethoxazole (SMX)). Under the optimized conditions (pyrolysis at 800 °C during 20 min and a KOH:PS ratio of 1:5), a microporous AC (MW800-20-1:5, with S_BET = 1196 m² g^-1, TOC = 56.2% and removal of AMX and SMX = 85% and 72%, respectively) was produced and selected for further kinetic and equilibrium adsorption studies. The obtained results were properly described by the Elovich reaction-based kinetic model and the Langmuir equilibrium isotherm, with maximum adsorption capacities of 204 ± 5 mg g^-1 and 217 ± 8 mg g^-1 for AMX and SMX, respectively. Considering the satisfactory comparison of these results with the performance of commercial and alternative AC produced by conventional pyrolysis, this work demonstrated the feasibility of the microwave-assisted production of environmentally and energetically sustainable waste-based AC to be applied in the efficient removal of antibiotics from water.

Adsorption of nitrification inhibitor nitrapyrin by humic acid and fulvic acid in black soil: characteristics and mechanism

The compound nitrapyrin is easily adsorbed by soil organic matter in high-organic matter soils, and this results in its effectiveness reducing significantly. In this study, the adsorption characteristics and mechanisms of nitrapyrin as an adsorptive on humic acid (HA) and fulvic acid (FA) as adsorbents were investigated. The results showed that the kinetics of adsorption of nitrapyrin on both HA and FA followed pseudo-second-order kinetic models (R² ≥ 0.925, P < 0.05) and the adsorption process included an initial fast-adsorption stage and a slow-adsorption stage thereafter. The adsorption efficiencies of nitrapyrin on HA + FA were higher than that on HA or FA alone, and that of HA was higher than that of FA. The adsorption isotherms of nitrapyrin on HA and FA could be optimally fitted with the Langmuir equation (R² ≥ 0.982, P < 0.05). The maximum adsorption capacities of nitrapyrin on HA, FA and HA + FA were 4896.49, 3173.70 and 4925.56 mg kg⁻¹, respectively. Synergistic adsorption of nitrapyrin in co-existing systems of HA and FA was also observed. The adsorption mechanism of nitrapyrin on both HA and FA involved hydrogen bonding and hydrophobic interaction. Therefore, HA and FA in the soil environment can adsorb a large amount of nitrapyrin and reduce its effectiveness, and they have a positive synergistic effect.

The compound nitrapyrin is easily adsorbed by soil organic matter in high-organic matter soils, and this results in its effectiveness reducing significantly.

Comparative analysis of linear and nonlinear equilibrium models for the removal of metronidazole by tea waste activated carbon

Tea waste was carbonized at 400 °C for 45 min and modified with potassium hydroxide (KOH), to enhance the active sites for the adsorption of antibiotics. The developed tea waste activated carbon (TWAC) was used as a novel eco-friendly and cost-effective adsorbent for metronidazole (MZN) removal from aqueous solution. The textural and surface properties of the adsorbent were determined using Brunauer-Emmett-Teller (BET) and FT-Raman analysis. The BET surface was found to have increased from 24.670 to 349.585 after carbonization and KOH modification. The batch experimental parameters were optimized and equilibrium time was found to be 75 min. Linear and non-linear models were carried out on the adsorption isotherm and kinetics to determine the best fit for the adsorption data. The adsorption equilibrium data were well fitted by the Freundlich isotherm and pseudo-second order models, with higher regression correlation (R²) and smaller chi-square (χ²), as predicted by the non-linear model. The thermodynamic results revealed the adsorption of MZN as spontaneous, physical, and consistently exothermic in character. The activation energy value of 7.610 kJ/mol further revealed that the adsorption process is dominated majorly by physical adsorption. The removal of MZN onto TWAC was best described by the non-linear adsorption isotherm and kinetics model.

Potential Use of Waste Activated Sludge Hydrothermally Treated as a Renewable Fuel or Activated Carbon Precursor

In this work, dewatered waste activated sludge (DWAS) was subjected to hydrothermal carbonization to obtain hydrochars that can be used as renewable solid fuels or activated carbon precursors. A central composite rotatable design was used to analyze the effect of temperature (140–220 °C) and reaction time (0.5–4 h) on the physicochemical properties of the products. The hydrochars exhibited increased heating values (up to 22.3 MJ/kg) and their air-activation provided carbons with a low BET area (100 m²/g). By contrast, chemical activation with K₂CO₃, KOH, FeCl₃ and ZnCl₂ gave carbons with a well-developed porous network (BET areas of 410–1030 m²/g) and substantial contents in mesopores (0.079–0.271 cm³/g) and micropores (0.136–0.398 cm³/g). The chemically activated carbons had a fairly good potential to adsorb emerging pollutants such as sulfamethoxazole, antipyrine and desipramine from the liquid phase. This was especially the case with KOH-activated hydrochars, which exhibited a maximum adsorption capacity of 412, 198 and 146 mg/g, respectively, for the previous pollutants.

Discarded biodiesel waste-derived lignocellulosic biomass as effective biosorbent for removal of sulfamethoxazole drug

This work aims to evaluate the removal of pharmaceutical drug using discarded biodiesel waste-derived lignocellulosic-based activated carbon biomaterial. Lignocellulosic-based activated carbon (LAC) biomaterial was prepared from Jatropha shell (biodiesel processing waste) by a zinc chloride activation method. The LAC biomaterial was characterized using various techniques including powder XRD, FT-IR, SEM-EDAX, and BET analysis. LAC biomaterial was applied to examine the adsorption of sulfamethoxazole (SMZ) drug in aqueous solution under ambient temperature. Various experimental parameters such as the effect of pH, treatment time, adsorbate concentration, and LAC dose of adsorption experiments were thoroughly examined and optimized. Under the optimal conditions, LAC biomaterial showed the maximum adsorption removal efficiency of SMZ drug. The kinetic models of Lagergren first-order, pseudo-second-order, intraparticle diffusion, and Bhangam's equation for SMZ removal onto LAC were used to recognize the probable mechanism of adsorption manner. From the experimental results, the Freundlich isotherm model (K_f = 83.56 mg g^-1 (L mg^-1)^1/n) shows similar fit than the Langmuir (Q₀ = 206.2 mg g^-1) and Dubinin-Radushkevich (Q_m = 150.69 mg g^-1) condition models of adsorption isotherms. The rate constants of adsorption were found to confirm the pseudo-first-order kinetic and Bhangam's models with a significant correlation. The separation factor (R_L) showed the favorable condition of the adsorption isotherm for the experimental system. The desorption results indicate that the ionic molecular exchange of SMZ from the hydroxyl group of LAC surface plays an important role in the recycling processes. Therefore, these results proved that the prepared low-cost LAC biomaterial could be used as an efficient adsorption material for the effective removal of pharmaceutical drugs in aqueous samples.

Preparation of composite adsorbents of activated carbon supported MgO/MnO2 and adsorption of Rhodamine B

Activated carbon (AC) was modified by MgO and MnO₂ through an impregnation-precipitation-calcination procedure. The batch experiments of adsorption of Rhodamine B (RB) by a modified adsorption material, an MgO-MnO₂-AC composite, were carried out and the characteristics of the composite adsorbent were evaluated. The results showed that manganese/magnesium loading changed the surface area, pore volume and increased the number of active adsorption sites of AC. The highest Brunauer-Emmett-Teller (BET) surface area (1,036.18 m²·g^-1) was obtained for MgO-MnO₂-AC compared with AC. The content of AC loaded with magnesium and manganese was 34.24 and 5.51 mg·g^-1 respectively. The adsorption of RB on MgO-MnO₂-AC was significantly improved. The maximum adsorption capacity of RB on MgO-MnO₂-AC was 16.19 mg·g^-1 at 25 °C under the RB concentration of 50 mg·L^-1. The adsorption of RB by AC and MgO-MnO₂-AC increased with the initial concentration of RB. The adsorption of RB increased first and then decreased when pH was between 3 and 11. The results indicated that the pseudo-second-order kinetic equation and Langmuir equation can be used to describe the adsorption of RB on MgO-MnO₂-AC.

Removal of metronidazole from aqueous media by C. vulgaris

This current study investigated the removal of metronidazole from aqueous media by C. vulgaris. Two different initial sizes of inoculum (0.05 and 0.5 g L^-1) were tested for a wide concentration range of metronidazole (1-50 μM). The effect of metronidazole concentrations on biomass production was studied for 20 days. The exopolymeric substances (EPS) were quantified and correlated with the removal of antibiotics from aqueous media. Specifically, MDZ stimulated the production of EPS in C. vulgaris, which played the major role in the adsorption of this antibiotic. Also, metronidazole significantly influenced the zeta potential of C. vulgaris in the test cultures, indicating a change in surface characteristics. This decrease in surface negative charge caused auto-flocculation phenomena at a stationary phase. Chronic and acute toxicity experiments showed that metronidazole was harmful to C. vulgaris at stationary phase. Results from this study would advance our knowledge on the treatment of metronidazole-contaminated waters with C. vulgaris as a green technology-oriented process.

Co-carbonization of biomass and oily sludge to prepare sulfamethoxazole super-adsorbent materials

Different biomass materials (walnut shell, coconut shell or cottonwood sawdust) were co-pyrolyzed with carbon-enriched oily sludge to produce aqueous phase sulfamethoxazole (SMZ) adsorption materials. The co-pyrolysis char was activated with K₂CO₃ to modify its micro-structure and functional groups. Results show that ACs prepared from the mixture contained more mesopores than biomass-based ACs, more porous and higher yield than oily sludge-based ACs. One-step activation method was more attractive than two-step activation in larger specific surface area (up to almost 4 times), wider pore size distribution (2-3 nm), stronger SMZ adsorption ability (higher than 2 times). The maximum BET surface area was 1342 m²/g for the ACs prepared from the mixture of walnut shell and oily sludge by one-step activation and it had the maximum SMZ adsorption capacity up to 361.9 mg/g, which is higher than previous reported values. The capacity of SMZ adsorption of ACs was mainly attributed to pore size distribution, specific surface area and functional groups. Among them, the appropriate content of CO and CO functional groups, larger specific area and more pores range from 2 to 3 nm lead to higher adsorption capacity.

Low-Cost Activated Grape Seed-Derived Hydrochar through Hydrothermal Carbonization and Chemical Activation for Sulfamethoxazole Adsorption

Activated carbons were prepared by chemical activation with KOH, FeCl3 and H3PO4 of the chars obtained via hydrothermal carbonization of grape seeds. The hydrochars prepared at temperatures higher than 200 °C yielded quite similar proximate and ultimate analyses. However, heating value (24.5–31.4 MJ·kg−1) and energy density (1.04–1.33) significantly increased with carbonization temperatures between 180 and 300 °C. All the hydrochars showed negligible BET surface areas, while values between 100 and 845 m2·g−1 were measured by CO2 adsorption at 273 K. Activation of the hydrochars with KOH (activating agent to hydrochar ratio of 3:1 and 750 °C) led to highly porous carbons with around 2200 m2·g−1 BET surface area. Significantly lower values were obtained with FeCl3 (321–417 m2·g−1) and H3PO4 (590–654 m2·g−1), showing these last activated carbons important contributors to mesopores. The resulting materials were tested in the adsorption of sulfamethoxazole from aqueous solution. The adsorption capacity was determined by the porous texture rather than by the surface composition, and analyzed by FTIR and TPD. The adsorption equilibrium data (20 °C) fitted the Langmuir equation well. The KOH-activated carbons yielded fairly high saturation capacity reaching up to 650 mg·g−1.

Modifying Nanoporous Carbon through Hydrogen Peroxide Oxidation for Removal of Metronidazole Antibiotics from Simulated Wastewater

This study examined change in pore structure and microstructure of nanoporous carbon after surface oxidation and how it affects the adsorption performance of metronidazole antibiotics. The surface oxidation was performed by hydrogen peroxide at 60 °C. The properties of porous carbon were investigated by N2-sorption analysis (pore structure), scanning electron microscopy (surface morphology), the Boehm titration method (quantification of surface functional group), and Fourier transform infrared spectroscopy (type of surface functional group). The results showed that the oxidation of porous carbon by hydrogen peroxide has a minor defect in the carbon pore structure. Only a slight decrease in specific surface area (8%) from its original value (973 m2g−1) was seen but more mesoporosity was introduced. The oxidation of porous carbon with hydrogen peroxide modified the amount of oxide groups i.e., phenol, carboxylic acid and lactone. Moreover, in the application the oxidized carbon exhibited a higher the metronidazole uptake capacity of up to three-times manifold with respect to the pristine carbon.

Adsorptive removal of nitroimidazole antibiotics from water using porous carbons derived from melamine-loaded MAF-6

Nitrogen-containing carbons were obtained via pyrolysis of melamine-loaded metal azolate frameworks (named mela@MAF-6), a sub-class of metal organic frameworks. The porosity and defect concentration of the obtained carbons (named as CDM@M-6) were dependent on the quantity of melamine loaded in the mela@MAF-6. The CDM@M-6 s were applied for the adsorptive removal of nitroimidazole antibiotics (NIABs) from water; the performance of CDM@M-6, particularly CDM(0.25)@M-6, was outstanding for the elimination of NIABs such as dimetridazole (DMZ), metronidazole (MNZ), and menidazole (MZ)) from water. The adsorption capacity of CDM(0.25)@M-6 for DMZ, MNZ, and MZ was higher than that of any adsorbent reported so far. The highest adsorptive performance of CDM(0.25)@M-6 for DMZ (Q₀: 621 mg/g) and MNZ (Q₀: 702 mg/g) was explained by hydrogen bonding, where CDM@M-6 and DMZ/MNZ acted as a H-donor and H-acceptor, respectively. In addition, CDM(0.25)@M-6 could be regenerated via ethanol washing and reused for next cycles without any severe decrease in performance. Therefore, CDM@M-6 is recommended as a suitable adsorbent for the elimination of NIABs from water.

Pharmaceutical emerging pollutants removal from water using powdered activated carbon: Study of kinetics and adsorption equilibrium

Pharmaceutical products and their byproducts which are present in wastewater and superficial water are becoming an environmental problem. A large effort has been made to introduce new and more efficient treatment processes for removing these emerging pollutants. Among them, activated carbon is currently being studied to be implemented in wastewater treatment plants. In the present study the equilibrium and kinetics of the adsorption of carbamazepine (Cbz) and sildenafil citrate (Sil) onto powdered activated carbon are presented. Batch experiments were performed to assess the potential of this kind of activated carbon for removing these recalcitrant pharmaceuticals from aqueous systems. In addition, its adsorption efficiency was compared with the granular activated carbon. The isotherms of Langmuir, Freundlich, Langmuir-Freundlich and Redlich-Peterson were applied. Pseudo-first and pseudo-second order models, as well as a combined model and an intraparticle diffusion model were assayed on the results obtained. Linear and non-linear analyses were carried out to compare the best fitting isotherms and kinetics. The Langmuir isotherm was a good fit for the adsorption of Sil, whereas the Redlich-Peterson isotherm described the adsorption of Cbz. The experimental results for both pharmaceuticals follow a kinetic of pseudo first order. Comparative studies preparing the solutions with distilled water, dechlorinated water and wastewater were performed. No significant differences were observed in these studies. When initial concentrations similar to those found in surface waters for both pharmaceuticals were evaluated, removal efficiencies greater than 85% were obtained. Therefore, the use of this kind of activated carbon seems to be an efficient tool for the removal of recalcitrant emerging pollutants, such as Sil and Cbz.

Effects of pyrolysis temperature on the physicochemical properties of alfalfa-derived biochar for the adsorption of bisphenol A and sulfamethoxazole in water

The present study reports alfalfa (one of most abundant hays in U.S)-derived biochar for effective removal of emerging contaminants in water for the first time. The physicochemical properties of alfalfa-derived biochar (AF-BC) made at various pyrolysis temperatures were investigated, and correlated with the adsorption of bisphenol A (BPA) and sulfamethoxazole (SMX) in water. The increase in pyrolysis temperatures from 350 °C to 650 °C for the pyrolysis of AF led to a drastic increase in surface area and carbonization with the loss of functional groups. The AF-derived biochar made at 650 °C showed much higher adsorption capacities for BPA and SMX than those made at 350-550 °C, mainly owing to the hydrophobic and π-π interactions supported by its high surface area and degree of carbonization. The adsorption isotherms fitted the Freundlich for BPA and Temkin models for SMX well, respectively. The adsorption capacities of AF 650 for BPA and SMX were higher than those of other biochars but lower than those of commercial activated carbon. The pH-dependent desorption for AF 650 showed high efficiency for SMX, but low efficiency for BPA indicating needs for alternative regeneration methods for BPA.

Theoretical study of adsorption characteristics and the environmental influence for metronidazole on photocatalytic TiO2 anatase surfaces

The adsorption characteristics of metronidazole on anatase TiO₂(101) and (001) surfaces were studied by density functional theory (DFT). The adsorption structure of metronidazole on anatase TiO₂(101) and (001) surfaces has been optimized under vacuum, water, acidic, and alkaline conditions, respectively. The optimum adsorption site, adsorption energy, and electronic structure of the stable adsorption model were calculated. The adsorption characteristics of metronidazole on two different surfaces of TiO₂ were studied under acidic and alkaline conditions. Our calculated results found that the adsorption energy range is -0.95 ~ -3.11 eV on the TiO₂ (101) surface, and the adsorption energy range is -0.84 ~ -3.29 eV on the TiO₂ (001) surface. The adsorption wavelengths of electron transition between valence band and conduction band of metronidazole on the anatase TiO₂(101) surface is in the range of visible wavelength, indicating that the TiO₂(101) surface can effectively utilize visible light. However, the photocatalytic effect of the TiO₂(001) surface is greatly affected by the environment. The results reveal the adsorption characteristics and the environmental influence for metronidazole on photocatalytic anatase TiO₂ surfaces. Graphical abstract The adsorption characteristics of metronidazole on anatase TiO₂(101) and (001) crystal surfaces were studied by density functional theory (DFT).

Metronidazole removal by means of a combined system coupling an electro-Fenton process and a conventional biological treatment: By-products monitoring and performance enhancement

In order to mineralize Metronidazole (MTZ), a process coupling an electro-Fenton pretreatment and a biological degradation was implemented. A mono-compartment batch reactor containing a carbon-felt cathode and a platinum anode was employed to carry out the electro-Fenton pretreatment of MTZ. A total degradation of MTZ (100 mg L^-1) was observed at 0.07 mA.cm^-2 after only 20 min of electrolysis. Yet, after 1 and 2 h of electrolysis, the mineralization level remained low (16.2% and 32% respectively), guaranteeing a significant residual organic content for further biological treatment. LCMS/MS was used to determine the intermediates by-products and hence to propose a plausible degradation pathway. An increase from 0 to 0.44 and 0.6 for 1 and 2 h of electrolysis was observed for the BOD₅/COD ratio. Thus, from 1 h of electro-Fenton pretreatment, the electrolysis by-products were considered biodegradable. A biological treatment of the electrolysis by-products after 1 and 2 h was then realized. The mineralization yields reached very close values, about 84% for 1 and 2 h of electrolysis after 504 h of biological treatment, namely close to 89% for the overall process, showing the pertinence of the proposed coupled process.

Removal of sulfamethoxazole (SMX) and sulfapyridine (SPY) from aqueous solutions by biochars derived from anaerobically digested bagasse

This study explored the sorption of sulfamethoxazole (SMX) and sulfapyridine (SPY) onto biochars produced from raw and anaerobically digested bagasse. Initial evaluation of six bagasse biochars showed that digested bagasse biochar prepared at 600 °C (DBG600) was the best adsorbent to remove SMX and SPY. Further laboratory batch sorption experiments showed that DBG600 adsorbed SMX and SPY from aqueous solution with maximum adsorption capacity of 54.38 and 8.60 mg g^-1, respectively. Solution pH showed strong effect on the sorption ability of DBG600 to the two antibiotics, and the sorption decreased with increasing of solution pH. Experimental and model results suggested that adsorption of SMX and SPY onto DBG600 might be controlled by the π-π interaction.