Kinetics, isotherms, effect of structure, and computational analysis during the removal of three representative pharmaceuticals from water by adsorption using a biochar obtained from oil palm fiber

Theoretical and experimental studies of cephalexin adsorption on aluminium as a new alternative of removal from wastewater

Cephalexin (CPX) is an antibiotic widely used to treat many infections. CPX has become an emerging pollutant present in wastewater. On the other hand, it is well known that organic compounds can be adsorbed over metal surfaces when the metal is in active state such as when it is rusting. This work proposes an alternative for the elimination of CPX from wastewater, applying electrochemical principles using a conventional and cheap substrate, aluminium. The first part consisted of obtaining the active states of aluminium electrodes carrying out voltametric curves at different pH (4, 7 and 9) to find the particular condition of interaction between CPX and metal surface. The potential was used in the potentiostatic tests to set the activation potential of metal at different times. After the treatment, electrolyte solutions were analysed using UV-vis spectra, and the aluminium surfaces were studied by optical micrographs and X-ray diffraction. In addition, aluminium-CPX interactions were corroborated by quantum-chemical calculations and adsorption isotherms. All results indicate that it was possible for the CPX removal at basic pH conditions, where the molecule adsorption on the aluminium substrate occurs due to a strong electrostatic interaction.

Treatment of dye-containing wastewater using discarded animal blood-derived hemoglobin crystals

Ever-expanding industrial and agricultural production has satisfied human needs but unfortunately causes serious environmental pollution. Pollutants such as dye-containing wastewater from the dye industry and animal blood waste from the meat industry impose heavy burdens on the environment and are difficult to treat. Here we demonstrate that hemoglobin crystals prepared from animal blood waste can effectively and selectively adsorb and remove organic pollutants from dye-containing wastewater. This approach simultaneously mitigates two types of environmental pollutants: wastewater dye and animal waste. The absorption properties of low-cost and stable cross-linked hemoglobin crystals (CLHCs) prepared from discarded chicken blood were experimentally tested on various dyes (methylene blue, malachite green, methyl orange and Congo red). The CLHCs adsorbed all dyes in a pH-dependent manner, achieving controllable selective adsorption. Adsorption of anionic dyes was especially effective, with an adsorption capacity of 184.18 mg/g for methylene blue. Unexpectedly, the CLHCs also exhibited degradative activity against methylene blue and malachite green. Mechanistic studies showed that the crystals removed methylene blue mainly by multi-layer physical adsorption and malachite green mainly by chemical degradation. Finally, we evaluated whether CLHCs can remove dyes from actual wastewater to promote the germination of contaminated rice seeds. Our results confirm that hemoglobin crystals can effectively treat dye-containing wastewater in practical scenarios.

Investigations on adsorptive removal of PVC microplastics from aqueous solutions using Pinus roxburghii-derived biochar

This study investigates the adsorption mechanisms of pine bark biochar (BC) and modified pine bark biochar (MBC) in the removal of polyvinyl chloride (PVC) microplastics from aqueous solutions, with a significant focus on resource recovery from pine residues which is one of the key Himalayan Forest byproducts. The research findings highlighted the optimal adsorption capacity of biochar at 131.5 mg/g achieved after 6 h of contact time, with a pH of 10 and a PVC microplastic concentration of 200 mg/L. The primary mechanisms of PVC microplastic adsorption involved ion exchange and physical adsorption, driven by forces such as Vander-Waals, London forces, and electrostatic forces. Thermodynamic analysis showed the exothermic nature of the PVC and BC/MBC interaction, with spontaneous adsorption occurring within the temperature range of 10 to 40 °C. Isotherm and kinetic models fit well with Temkin model and PSO kinetics, as indicated by R2 values exceeding 0.9. Particularly, MBC exhibited superior removal efficiency and adsorption capacity compared to its precursor, reaching an optimum adsorption capacity of 156.08 mg/g with a removal efficiency of 78%, surpassing the performance of BC. This research contributes valuable insights into potential applications of BC for PVC removal and underscores the effectiveness of MBC in achieving enhanced adsorption outcomes.

Chemometrically-aided general approach to novel adsorbents studies: Case study on the adsorption of pharmaceuticals by the carbonized Ailanthus altissima leaves

A chemometrically based approach was applied to select the most efficient drug adsorbent among the biochars obtained from the novel feedstock, the leaves of the invasive plant (Ailanthus altissima). The representative target adsorbates (atenolol, paracetamol, ketorolac and tetracycline) were selected on the basis of their physicochemical properties to cover a wide chemical space, which is the usual analytical challenge. Their adsorption was investigated using design of experiments as a comprehensive approach to optimise the performance of the adsorption system, rationalise the procedure and overcome common drawbacks. Among the response surface designs, the central composite design was selected as it allows the identification of important experimental factors (solid-to-liquid ratio, pH, ionic strength) and their interactions, and allows the selection of optimal experimental conditions to maximise adsorption performance. The biochars were prepared by pyrolysis at 500 °C and 800 °C (BC-500 and BC-800) and the ZnCl2-activated biochars were prepared at 650 °C and 800 °C (AcBC-650 and AcBC-800). The FTIR spectra revealed that increasing the pyrolysis temperature without activator decreases the intensity of all bands, while activation preserves functional groups, as evidenced by the spectra of AcBC-650 and AcBC-800. High temperatures during activation promoted the development of an efficient surface area, with the maximum observed for AcBC-800 reaching 347 m2 g-1. AcBC-800 was found to be the most efficient adsorbent with removal efficiencies of 34.1, 51.3, 55.9 and 38.2 % for atenolol, paracetamol, ketorolac and tetracycline, respectively. The models describing the relationship between the removal efficiency of AcBC-800 and the experimental factors studied, showed satisfactory predictive ability (predicted R2 > 0.8) and no significant lack-of-fit was observed. The results obtained, including the mathematical models, the properties of the adsorbates and the adsorbents, clearly indicate that the adsorption mechanisms of activated biochars are mainly based on hydrophobic interactions, pore filling and hydrogen bonding.

Biochar-based functional materials for the abatement of emerging pollutants from aquatic matrices

Biochar has emerged as a versatile and efficient multi-functional material, serving as both an adsorbent and catalyst in removing emerging pollutants (EPs) from aquatic matrices. However, pristine biochar's catalytic and adsorption capabilities are hindered by its poor surface functionality and small pore size. Addressing these limitations involves the development of functionalized biochar, a strategic approach aimed at enhancing its physicochemical properties and improving adsorption and catalytic efficiencies. Despite a growing interest in this field, there is a notable gap in existing literature, with no review explicitly concentrating on the efficacy of biochar-based functional materials (BCFMs) for removing EPs in aquatic environments. This comprehensive review aims to fill this void by delving into the engineering considerations essential for designing BCFMs with enhanced physiochemical properties. The focus extends to understanding the treatment efficiency of EPs through mechanisms such as adsorption or catalytic degradation. The review systematically outlines the underlying mechanisms involved in the adsorption and catalytic degradation of EPs by BCFMs. By shedding light on the prospects of BCFMs as a promising multi-functional material, the review underscores the imperative for sustained research efforts. It emphasizes the need for continued exploration into the practical implications of BCFMs, especially under environmentally relevant pollutant concentrations. This holistic approach seeks to contribute to advancing knowledge and applying biochar-based solutions in addressing the challenges posed by emerging pollutants in aquatic ecosystems.

Boosting acetaminophen degradation in water by peracetic acid activation: A novel approach using chestnut shell-derived biochar at varied pyrolysis temperatures

In this study, biochar derived from chestnut shells was synthesized through pyrolysis at varying temperatures from 300 °C to 900 °C. The study unveiled that the pyrolysis temperature is pivotal in defining the physical and chemical attributes of biochar, notably its adsorption capabilities and its role in activating peracetic acid (PAA) for the efficient removal of acetaminophen (APAP) from aquatic environments. Notably, the biochar processed at 900 °C, referred to as CN900, demonstrated an exceptional adsorption efficiency of 55.8 mg g-1, significantly outperforming its counterparts produced at lower temperatures (CN300, CN500, and CN700). This enhanced performance of CN900 is attributed to its increased surface area, improved micro-porosity, and a greater abundance of oxygen-containing functional groups, which are a consequence of the elevated pyrolysis temperature. These oxygen-rich functional groups, such as carbonyls, play a crucial role in facilitating the decomposition of the O-O bond in PAA, leading to the generation of reactive oxygen species (ROS) through electron transfer mechanisms. This investigation contributes to the development of sustainable and cost-effective materials for water purification, underscoring the potential of chestnut shell-derived biochar as an efficient adsorbent and catalyst for PAA activation, thereby offering a viable solution for environmental cleanup efforts.

The effect of the ageing process on the desorption of nonylphenol in black carbon-sediment systems: a kineto-mechanistic and modeling investigation

Black carbon (BC) exhibits promising potential as a sediment amendment owing to its commendable adsorption capacity for hydrophobic organic contaminants (HOCs), thereby resulting in HOC-laden sediments. Desorption kinetic studies play a crucial role in comprehending the release potential of HOCs from BC-sediment systems. Although the adsorption capacity of BC for HOCs has been found to decrease with aging, there is limited research on its impact on HOC desorption kinetics. In this study, BCs derived from agricultural waste (rice straw carbon, RC) and industrial waste (fly ash carbon, FC), respectively, were used to investigate the desorption kinetics of nonylphenol (NP). Additionally, a predictive model was established using the fitting parameters obtained from the modified two-domain model. The results showed that desorption of NP was divided into three fractions: rapid fraction (Frap), slow fraction (Fslow) and resistant fraction (Fr). BCs significantly decreased, while ageing increased the desorption amount and rate of NP. The performance of RC in controlling NP release was superior to that of FC. The predicted values calculated by the established model exhibit significant positive correlations with the measured values (p < 0.01). Additionally, the correlation analysis between sorption sites and desorption fractions revealed that the concentration of NP in the desorbing fraction was nearly equivalent to that of NP in partition sites within aged sediment/FC-sediment systems. However, the aged RC-sediment systems do not conform well to this rule. In other words, the estimation of NP release risk from sediments with a strong adsorbent would be overestimated, if Frap + Fsolw is considered equivalent to the desorbing fraction.

Effect of organic acids on the solid-state polymorphic phase transformation of piracetam

Metastable polymorphs are frequently used in oral solid dosage forms to enhance the absorption of poorly water-soluble drug compounds. However, the solid phase transformation from the metastable polymorph to the thermodynamically stable polymorph during manufacturing or storage poses a major challenge for product development and quality control. Here, we report that low-content organic acids can exhibit distinct effects on the solid-state polymorphic phase transformation of piracetam (PCM), a nootropic drug used for memory enhancement. The addition of 1 mol% citric acid (CA) and tricarballylic acid (TA) can significantly inhibit the phase transformation of PCM Form I to Form II, while glutaric acid (GA) and adipic acid (AA) produce a minor effect. A molecular simulation shows that organic acid molecules can adsorb on the crystal surface of PCM Form I, thus slowing the movement of molecules from the metastable form to the stable form. Our study provides deeper insights into the mechanisms of solid-state polymorphic phase transformation of drugs in the presence of additives and facilitates opportunities for controlling the stability of metastable pharmaceuticals.

Textile Waste-Derived Cobalt Nanoparticles Embedded in Active Carbon Fiber for Efficient Activation of Peroxymonosulfate to Remove Organic Pollutants

Burning and dumping textile wastes have caused serious damage to the environment and are a huge waste of resources. In this work, cobalt nanoparticles embedded in active carbon fiber (Co/ACF) were prepared from bio-based fabric wastes, including cotton, flax and viscose. The obtained Co/ACF was applied as a catalyst for the heterogeneous activation of peroxymonosulfate (PMS) to remove bisphenol A (BPA) from an aqueous solution. The results showed that cotton-, flax- and viscose-derived Co/ACF all exhibited excellent performance for BPA degradation; over ~97.0% of BPA was removed within 8 min. The Co/ACF/PMS system exhibited a wide operating pH range, with a low consumption of the catalyst (0.1 g L-1) and PMS (0.14 g L-1). The high specific surface area (342 m2/g) and mesoporous structure of Co/ACF allowed the efficient adsorption of pollutants as well as provided more accessible active sites for PMS activation. This study provided an example of using textile wastes to produce a valuable and recyclable catalyst for environmental remediation.

Insights into Recent Advances of Biomaterials Based on Microbial Biomass and Natural Polymers for Sustainable Removal of Pharmaceuticals Residues

Pharmaceuticals are acknowledged as emerging contaminants in water resources. The concentration of pharmaceutical compounds in the environment has increased due to the rapid development of the pharmaceutical industry, the increasing use of human and veterinary drugs, and the ineffectiveness of conventional technologies to remove pharmaceutical compounds from water. The application of biomaterials derived from renewable resources in emerging pollutant removal techniques constitutes a new research direction in the field. In this context, the article reviews the literature on pharmaceutical removal from water sources using microbial biomass and natural polymers in biosorption or biodegradation processes. Microorganisms, in their active or inactive form, natural polymers and biocomposites based on inorganic materials, as well as microbial biomass immobilized or encapsulated in polymer matrix, were analyzed in this work. The review examines the benefits, limitations, and drawbacks of employing these biomaterials, as well as the prospects for future research and industrial implementation. From these points of view, current trends in the field are clearly reviewed. Finally, this study demonstrated how biocomposites made of natural polymers and microbial biomass suggest a viable adsorbent biomaterial for reducing environmental pollution that is also efficient, inexpensive, and sustainable.

Effective removal of selected pharmaceuticals from sewerage treatment plant effluent using natural clay (Na-montmorillonite)

The consumption of pharmaceuticals has rapidly increased on a global scale due to the serious increase in Covid-19, influenza and respiratuar sinsityal virus, which is called "triple epidemic" in the world. The use of non-prescription analgesic and anti-inflammatory drugs (AAIDs), especially paracetamol, is higher compared to pre-pandemic. This increased the AAIDs load discharged to the aqueous media through sewerage treatment plant (STP). Therefore, simple and effective treatment options for removing AAIDs from STP effluents are needed. The aim of the study was to remove AAIDs (paracetamol, acetylsalicylic acid, codeine, diclofenac, ibuprofen, indomethacin, ketoprofen, mefenamic acid, naproxen, and phenylbutazone) from STP effluents by nearly pure natural clay Na-montmorillonite. The Na-montmorillonite taken from the Ordu region in the northern part of Turkey. Surface area of the Na-montmorillonite is 99.58 m2/g and CEC is 92.40 meq/100 g. The removal efficiencies of AAIDs using Na-montmorillonite were between 82 ± 5% (ibuprofen) and 94 ± 4% (naproxen). Paracetamol was used as a model compound in kinetic and isotherm model studies. Freundlich isotherm model and the pseudo second order kinetic model were the best-fit using the obtained experimental data. Film diffusion governed its rate mechanism. The paracetamol adsorption capacity was acquired as 244 mg/g at 120 min contact time at pH 6.5 at 25 °C. With this study, it could be shown that montmorillonite can be used effectively to eliminate paracetamol from STP effluent. Natural clay can be used as a simple, inexpensive and effective adsorbent for removing AAIDs from STP effluents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13201-023-01930-5.

Insight into the effects of H2SO4 and HNO3 acidification processes on the properties of coal as an enhanced adsorbent for ciprofloxacin residuals: Steric and energetic studies

A sub-bituminous natural coal sample (R.C) was treated with sulfuric acid (S.C) and nitric acid (N.C) as modified products and enhanced adsorbents for obtaining ciprofloxacin (CFX) antibiotic residuals from water. The characterization studied demonstrates enhancement in the surface area and the incorporation of new active oxygenated, sulfur-bearing, and nitrogen-bearing chemical groups into the structure of coal samples. This was reflected in the adsorption capacities that were enhanced from 164.08 mg/g (R.C) to 489.2 mg/g and 518.5 mg/g for N.C and S.C, respectively. The impact of the acid modification processes was evaluated based on the energetic and steric properties of their adsorption systems considering the parameters of the advanced monolayer equilibrium model with one energy site. The determined occupied active sites’ density of R.C (46.32–61.44 mg/g), N.C (168.7–364.9 mg/g), and S.C (159.2–249.9 mg/g) reflects an increase in the quantities of active centers after the acid treatment processes, especially with HNO3. The higher efficiencies of the active sites of S.C to adsorb more CFX molecules (n = 2.08–2.31) than N.C (n = 1.41–2.16) illustrate its higher adsorption capacity. The energetic investigation [adsorption (˂40 kJ/mol) and Gaussian (˂8 kJ/mol) energies] suggested adsorption of CFX by N.C and S.C mainly by physical processes such as van der Waals forces, hydrogen bonding, dipole bonding, and π–π interactions. Moreover, the determined thermodynamic functions including entropy, internal energy, and free enthalpy reflect the spontaneous and endothermic uptake of CFX on the surfaces of N.C and S.C.

Chlorination disinfection by-products in Southeast Asia: A review on potential precursor, formation, toxicity assessment, and removal technologies

This review discusses disinfection by-products' (DBPs) potential precursors, formation, and toxicity, alongside available research on the treatment of DBPs in Southeast Asian countries' water sources. Although natural organic matter (NOM) in the form of humic and fulvic acids is the major precursor of DBPs formation, the presence of anthropogenic organic matter (AOM) also plays essential roles during disinfection using chlorine. NOM has been observed in water sources in Southeast Asian countries, with a relatively high concentration in peat-influenced water sources and a relatively low concentration in non-peat-influenced water sources. Similarly, AOMs, such as microplastics, pharmaceuticals, pesticides, and endocrine-disrupting chemicals (EDCs), have also been detected in water sources in Southeast Asian countries. Although studies regarding DBPs in Southeast Asian countries are available, they focus on regulated DBPs. Here, the formation potential of unregulated DBPs is also discussed. In addition, the toxicity associated with extreme DBPs' formation potential, as well as the effectiveness of treatments such as conventional coagulation, filtration, adsorption, and ozonation in reducing DBPs' formation potential in Southeast Asian sources of water, is also analyzed.

Acetaminophen adsorption to spherical carbons hydrothermally synthesized from sucrose: experimental, molecular, and mathematical modeling studies

Acetaminophen (AAP) is an analgesic and non-steroidal anti-inflammatory drug and a micropollutant that has been detected in waterbodies worldwide. Here, we explore the characteristics of AAP adsorption onto spherical carbons (SCs) hydrothermally synthesized from pure sucrose as a carbon source. In one-factor-at-a-time experiments, the adsorption capacity of AAP remained relatively constant between pH 2 and 10 but became negligible at pH 12. The Raman, FTIR, and XPS spectra illustrate that hydrogen bonding, π-π interactions, and n-π^* interactions could contribute to the AAP adsorption onto the SCs. CHEM3D modeling was used to explore hydrogen-bond formation, π-π interactions, n-π^* interactions, and electrostatic repulsion between AAP and the SCs. In view of the pH_pzc of the SCs (3.1) and the pKa of AAP (10.96), electrostatic repulsion could occur between negatively charged SCs and anionic AAP above pH 10. In consideration of the average pore diameter of the SCs (1.89 nm) and the AAP molecular size (8.94 Å × 7.95 Å × 4.93 Å), a pore-filling mechanism could contribute to the adsorption. A pseudo-second-order model was best fitted to the kinetic data (equilibrium time = 6 h), whereas the Liu isotherm was most suitable for the equilibrium data (maximum adsorption capacity = 92.0 mg/g). Adsorption of AAP to the SCs was exothermic at 10-40 °C. The SCs were regenerated and reused for AAP adsorption using a methanol. Multiple-factor-at-once (MFAO) experiments (input variables: pH, temperature, adsorbent dosage, and initial AAP concentration; output: AAP adsorption capacity) were used to develop response surface methodology (RSM, quartic regression) and artificial neural network (ANN, topology 4:11:9:1) models. Analyses using additional MFAO experimental data reveal that the predictive ability of the ANN model (R² = 0.890) was better than that of the RSM model (R² = 0.764). Based on the weight values of the ANN model, the relative importance of the input variables on the output was quantified in the order of initial AAP concentration (100%) > adsorbent dosage (92.3%) > temperature (77.6%) > pH (43.6%).

Biochar-mediated removal of pharmaceutical compounds from aqueous matrices via adsorption

Pharmaceutical is one of the noteworthy classes of emerging contaminants. These biologically active compounds pose a range of deleterious impacts on human health and the environment. This is attributed to their refractory behavior, poor biodegradability, and pseudopersistent nature. Their large-scale production by pharmaceutical industries and subsequent widespread utilization in hospitals, community health centers, and veterinary facilities, among others, have significantly increased the occurrence of pharmaceutical residues in various environmental compartments. Several technologies are currently being evaluated to eliminate pharmaceutical compounds (PCs) from aqueous environments. Among them, adsorption appears as the most viable treatment option because of its operational simplicity and low cost. Intensive research and development efforts are, therefore, currently underway to develop inexpensive adsorbents for the effective abatement of PCs. Although numerous adsorbents have been investigated for the removal of PCs in recent years, biochar-based adsorbents have garnered tremendous scientific attention to eliminate PCs from aqueous matrices because of their decent specific surface area, tunable surface chemistry, scalable production, and environmentally benign nature. This review, therefore, attempts to provide an overview of the latest progress in the application of biochar for the removal of PCs from wastewater. Additionally, the fundamental knowledge gaps in the domain knowledge are identified and novel strategic research guidelines are laid out to make further advances in this promising approach towards sustainable development.

Biochar from palm fiber wastes as an activator of different oxidants for the elimination of pharmaceuticals from diverse classes in aqueous samples

Biochar (BP) obtained from palm fiber wastes was combined with H₂O₂, peroxymonosulfate (PMS), or persulfate (PDS) to treat valsartan, acetaminophen, and cephalexin in water. BP activated PMS and PDS but no H₂O₂. Computational calculations indicated that interactions of PMS and PDS with BP are more favored than those with HP. The highest synergistic effect was obtained for the removal of valsartan by BP + PMS. This carbocatalytic process was optimized, evaluating the effects of pH, BP dose, and peroxymonosulfate concentration, and minimizing the oxidant quantity to decrease costs and environmental impacts of the process. SO₄•^-, HO•, ¹O₂, and O₂•^- were the agents involved in the degradation of the pharmaceuticals. The reusability of BP was tested, showing that the carbocatalytic process removed ∼80% of target pollutants after 120 min of treatment even at the fourth reuse cycle. Also, the process decreased the phytotoxicity of the treated sample. Simulated hospital wastewater was treated and its components induced competing effects, but the system achieved the target pharmaceuticals removal in this matrix. Additionally, the analysis of environmental impact using a life cycle assessment unraveled that the carbocatalytic process had a carbon footprint of 2.87 Kg CO₂-Eq, with the biochar preparation (which involves the use of ZnCl₂ and electric energy consumption) as the main hotspot in the process.

Removal of micropollutants through bio-based materials as a transition to circular bioeconomy: Treatment processes involved, perspectives and bottlenecks

The recent increase in micropollutant levels in water bodies is a growing concern globally. The generation of new materials and techniques for wastewater treatment often involves the release of hazardous wastes and the utilization of energy related to it. This can be resolved by the synthesis of bio-based materials through the use of already released wastes and naturally occurring components, adding their value as reusable resources. These bio-based materials find wide applications for micropollutant elimination and energy tapping due to the presence of various functional groups, large surface area, high stability, and reusability. The processes involved in micropollutant elimination through biomaterials generally include adsorption and degradation. These treatment processes are suggested to depend on various operational parameters like pH, temperature, dose, reaction time, presence of other contaminants, ions, etc. in the system, which may influence the process efficiency. Understanding the potential of bio-based materials many steps can be taken towards its large-scale application to upgrade wastewater treatment plants for micropollutant elimination. Furthermore, the recent advances of bio-based materials in energy storage and conversion have widened its scope for implementation in a circular bioeconomy. The bottlenecks towards such a transition and future recommendations are also presented and discussed.

Remediation of emerging metal pollutants using environment friendly biochar- Review on applications and mechanism

Bioremediation of heavy metals has become a major environmental concern due to their bio resistant nature and tendency to accumulate. Application of various technologies, involving physical and chemical working principles are applied and passive uptake using sorption involving eco-friendly substrates gained significant attention. Biochar, a cheaper and efficient material, offers good potential due to the greater ease of production, treatment and disposal. This review focuses on the effective application of biochar to treat water contaminated by three specific heavy metals: chromium, lead and arsenic. The on-field applications like soil amendment, industrial wastewater treatment and groundwater treatment using biochar are highlighted. The review article describes the feedstock available for biochar production, various production processes and the importance of optimum conditions like pyrolysis temperature, rate and retention time for various feedstocks reported in literature. The energy requirement of the production process can be supplied by its own energy output. Various modifications that are suitable for the biochar from distinct feedstocks are also discussed. The removal performance of biochar at different working conditions like pH, initial concentration of pollutant and adsorbent dose are consolidated. The highest removal efficiencies reported were by coconut shell biochar (Cr - 99.9%), canola straw biochar (Pb - 100%) and perilla leaf biochar (As - 100%). The adsorption mechanism is explained with reference to kinetics, isotherms, and molecular dynamics. Adsorption mechanism of most of the biochars was found to fit either Freundlich or Langmuir isotherm.

Engineered mesoporous biochar derived from rice husk for efficient removal of malachite green from wastewaters

Extremely soluble Malachite green (MG) acts as potential carcinogen for aquatic life in polluted aqueous environments. Current study aims to modify rice husk derived biochar to improve its removal efficiency for MG from MG-containing wastewaters. The hydrothermal alkali activation was effective for preparing modified biochar (RHMB) from native biochar (RHB) derived from rice husk. After modification, surface area and pore volume of RHMB was determined respectively 434.62 m²g^-1 and 287.28 cm³g^-1, significantly improved from native RHB values 21.764 m²g^-1 and 65.53 cm³g^-1. Pseudo second order kinetic model fitted well. RHMB exhibits an equilibrium adsorption capacity of 373.02 mg g^-1. RHMB showed an excellent MG removal ability and was not susceptible to ion interference even at highly saline environments. It has exhibited 96.96 ± 1.17% removal efficiency of MG and is expected to be used as potential adsorbent for MG remediation from aquaculture wastewater and other MG containing industrial wastewaters.

Catalytic degradation of sulfamethoxazole by peroxymonosulfate activation system composed of nitrogen-doped biochar from pomelo peel: Important roles of defects and nitrogen, and detoxification of intermediates

Nitrogen doping could improve the catalytic performance of carbon materials, in which the nitrogen configuration could be used as active sites for peroxymonosulfate (PMS) activation. Herein, this paper studied how to turn waste to "treasure" by agriculture waste pomelo peel to prepare nitrogen-doped biochar and successfully applied it to advanced oxidation field. The effects of the sodium bicarbonate (NaHCO₃), melamine, and pyrolysis temperature on the catalytic activity of biochar for the removal of sulfamethoxazole (SMX) were investigated. The optimized nitrogen-doped biochar (C-N-M 1:3:4) possessed high specific surface area (SSA, 738 m²/g) and high level of nitrogen doping (nitrogen content 13.54 at%). Accordingly, it exhibited great catalytic performance for PMS activation to remove SMX antibiotic, and 95% of SMX was removed within 30 min. High catalytic activity of C-N-M 1:3:4 was attributed to rich defects, carbonyl group, high content of graphitic N and pyrrolic N, and large SSA, in which non-radical oxidation process based on singlet oxygen (¹O₂) and electron transfer contributed to the SMX degradation. The prepared nitrogen-doped biochar possessed high stability and reusability and the removal efficiency of SMX still reached 80% after four cycles. Additionally, the phytotoxicity assay indicated that the toxicity of degradation intermediates was obviously decreased in the PMS/ C-N-M 1:3:4 system.

Unraveling the Ca-P species produced over the time during phosphorus removal from aqueous solution using biocomposite of eggshell-palm mesocarp fiber

Phosphorus (P) adsorption from aqueous solutions is usually evaluated by monitoring the P concentration and employed kinetic models. In this work, three adsorbents obtained from eggshell (ES) and eggshell mixed with palm mesocarp fiber (ESF-1:1 and ESF-1:10) at different Ca(OH)₂/CaCO₃ compositions were evaluated, and the Ca-P species formed monitored as a function of time deconvoluting Fourier Transform Infrared (FTIR) spectra. At 0.25 h the ESF-1:10 (Ca(OH)₂: 26.2 wt%) exhibited better adsorption performance of 35 mgg^-1 while ESF-1:1 and ES (Ca(OH)₂: 2.8 and 3.0 wt%) showed 26 and 4 mgg^-1, respectively. Characteristic PO₄^3- bands in apatite were corroborated by XRD and FTIR. It was found that the role of Ca(OH)₂ in the adsorption ends before 0.25 h, and thereafter CaCO₃ becomes the phase responsible for the removal of orthophosphate H₂PO₄^-/HPO₄^2-/PO₄^3- ions. The results indicate a direct ligand exchange of CO₃^2- for PO₄^3- that takes place while increasing the apatite crystallinity. On the other hand, the P adsorption process is also dependent on P concentration. At low P concentrations, characteristic bands of PO₄^3- in apatite were observed in FTIR, while at high concentrations, characteristic bands for adsorbed HPO₄^2- were obtained. The obtained results give a relevant role to CaCO₃ in P adsorption. Kinetic analysis for Ca-based biocomposites showed that the Avrami order kinetic model fits better for the adsorbents. For P adsorption isotherm process the Langmuir's isotherms showed a good fit, with a maximum adsorption capacity of 90.8, 134.0, and 67.9 mgg^-1 for ES, ESF-1:1, and ESF-1:10, respectively.

Optimization of ketoprofen adsorption from aqueous solutions and simulated effluents using H2SO4 activated Campomanesia guazumifolia bark

This study used the bark of the forest species Campomanesia guazumifolia modified with H₂SO₄ to absorb the anti-inflammatory ketoprofen from aqueous solutions. FTIR spectra confirmed that the main bands remained after the chemical treatment, with the appearance of two new bands related to the elongation of the carbonyl group present in hemicellulose. Micrographs confirmed that the surface started to contain a new textural shape after acid activation, having new pores and cavities. The drug adsorption's optimum conditions were obtained by response surface methodology (RSM). The adsorption was favored at acidic pH (2). The dosage of 1 g L^-1 was considered ideal, obtaining good indications of removal and capacity. The Elovich model very well represented the kinetic curves. The isotherm studies indicated that the increase in temperature negatively affected the adsorption of ketoprofen. A maximum adsorption capacity of 158.3 mg g^-1 was obtained at the lower temperature of 298 K. Langmuir was the best-fit isotherm. Thermodynamic parameters confirmed the exothermic nature of the system (ΔH⁰ = -8.78 kJ mol^-1). In treating a simulated effluent containing different drugs and salts, the removal values were 35, 50, and 80% at 15, 30, and 180 min, respectively. Therefore, the development of adsorbent from the bark of Campomanesia guazumifolia treated with H₂SO₄ represents a remarkable alternative for use in effluent treatment containing ketoprofen.

Removal of contaminants of emerging concern from multicomponent systems using carbon dioxide activated biochar from lignocellulosic feedstocks

Adsorption of six contaminants of emerging concern (CECs) - caffeine, chloramphenicol, carbamazepine, bisphenol A, diclofenac, and triclosan - from a multicomponent solution was studied using activated biochars obtained from three lignocellulosic feedstocks: wheat straw, softwood, and peach stones. Structural parameters related to the porosity and ash content of activated biochar and the hydrophobic properties of the CECs were found to influence the adsorption efficiency. For straw and softwood biochar, activation resulted in a more developed mesoporosity, whereas activation of peach stone biochar increased only the microporosity. The most hydrophilic CECs studied, caffeine and chloramphenicol, displayed the highest adsorption (22.8 and 11.3 mg g^-1) onto activated wheat straw biochar which had the highest ash content of the studied adsorbents (20 wt%). Adsorption of bisphenol A and triclosan, both relatively hydrophobic substances, was highest (31.6 and 30.2 mg g^-1) onto activated biochar from softwood, which displayed a well-developed mesoporosity and low ash content.

Application of Saccharomyces cerevisiae/Calcium Alginate Composite Beads for Cephalexin Antibiotic Biosorption from Aqueous Solutions

Cephalexin (CPX) is recognized as a water pollutant, and it has been listed in a number of countries with a risk factor greater than one. Herein, the present work focused on the synthesis, characterization and biosorption capacity evaluation of Saccharomyces cerevisiae immobilized in calcium alginate as a biosorbent to remove CPX from aqueous solutions. Biosorbent was characterized by SEM and FTIR techniques. Batch biosorption experiments were conducted in order to evaluate the effect of the initial pH, biosorbent dose and CPX initial concentration. The removal efficiency, in considered optimal conditions (pH = 4, CPX initial concentration = 30 mg/L, biosorbent dose = 1 g/L) was 86.23%. CPX biosorption was found to follow the pseudo–second-order kinetics. The equilibrium biosorption data were a good fit for the Langmuir model with correlation coefficient of 0.9814 and maximum biosorption capacity was 94.34 mg/g. This study showed that the synthesized biosorbent by immobilization technique is a low-cost one, easy to obtain and handle, eco-friendly, with high feasibility to remove CPX antibiotic from aqueous solution. The findings of this study indicate that the biosorbents based on microorganisms immobilized on natural polymers have the potential to be applied in the treatment of wastewater.

Evaluating the Removal of the Antibiotic Cephalexin from Aqueous Solutions Using an Adsorbent Obtained from Palm Oil Fiber

This study aimed to understand the adsorption process of cephalexin (CPX) from aqueous solution by a biochar produced from the fiber residue of palm oil. Scanning electron microscopy, Fourier transform infrared spectroscopy, Boehm titration, and the point of zero charge were used to characterize the morphology and surface functional groups of the adsorbent. Batch tests were carried out to evaluate the effects of the solution pH, temperature, and antibiotic structure. The adsorption behavior followed the Langmuir model and pseudo-second-order model with a maximum CPX adsorption capacity of 57.47 mg g^-1. Tests on the thermodynamic behavior suggested that chemisorption occurs with an activation energy of 91.6 kJ mol^-1 through a spontaneous endothermic process. Electrostatic interactions and hydrogen bonding represent the most likely adsorption mechanisms, although π-π interactions also appear to contribute. Finally, the CPX removal efficiency of the adsorbent was evaluated for synthetic matrices of municipal wastewater and urine. Promising results were obtained, indicating that this adsorbent can potentially be applied to purifying wastewater that contains trace antibiotics.