Two-stage preparation of highly mesoporous carbon for super-adsorption of paracetamol and tetracycline in water: Important contribution of pore filling and π-π interaction

Highly enhanced chloramphenicol adsorption performance of MIL-53-NH2(Al)-derived porous carbons modified with tannic acid

The worldwide demand for antibiotics has experienced a notable surge, propelled by the repercussions of the COVID-19 pandemic and advancements in the global healthcare sector. A prominent challenge confronting humanity is the unregulated release of antibiotic-laden wastewater into the environment, posing significant threats to public health. The adoption of affordable carbon-based adsorbents emerges as a promising strategy for mitigating the contamination of antibiotic wastewater. Here, we report the synthesis of novel porous carbons (MPC) through a direct pyrolysis of MIL-53-NH2(Al) and tannic acid (TANA) under N2 atmosphere at 800 °C for 4 h. The effect of TANA amount ratios (0%-20%, wt wt-1) on porous carbon structure and adsorption performance was investigated. Results showed that TANA modification resulted in decreased surface area (1,600 m2 g-1-949 m2 g-1) and pore volume (2.3 cm3 g-1-1.7 cm3 g-1), but supplied hydroxyl functional groups. Adsorption kinetic, intraparticle diffusion, and isotherm were examined, indicating the best fit of Elovich and Langmuir models. 10%-TANA-MPC obtained an ultrahigh adsorption capacity of 564.4 mg g-1, which was approximately 2.1 times higher than that of unmodified porous carbon. 10%-TANA-MPC could be easily recycled up to 5 times, and after reuse, this adsorbent still remained highly stable in morphology and surface area. The contribution of H bonding, pore-filling, electrostatic and π-π interactions to chloramphenicol adsorption was clarified. It is recommended that TANA-modified MIL-53-NH2(Al)-derived porous carbons act as a potential adsorbent for removal of pollutants effectively.

A comprehensive review on the production of durian fruit waste-derived bioadsorbents for water treatment

Global water pollution by various pollutants is becoming an urgent problem. The conversion of durian fruit waste into adsorbents can help to mitigate this issue. Transforming durian waste into adsorbents can reduce pollution risk from waste discharged directly into the environment, while also effectively eliminating existing contaminants. Here, this work explores the potential of durian fruit waste and supplies insights into the synthesis and application of durian fruit waste-derived adsorbents such as biosorbents, modified-biosorbents, biochars, activated carbons, and composites. Several factors affecting the adsorption process of pollutants and the mechanism how pollutants can be adsorbed onto durian fruit waste-derived adsorbents are elucidated. This review also analyzes some aspects of limitations and prospects of biosorbents derived from durian fruit waste. It is anticipated that the promising properties and applications of durian fruit waste-derived adsorbents open up a new field for water waste treatment.

Diclofenac sodium and paracetamol removal with ZnCl2 activated carbon produced from rice straw

This study explored the efficacy of activated carbon derived from rice straw and treated with ZnCl2 (ZnCl2-RS) for the removal of diclofenac sodium (DCF) and paracetamol (PCM) through an adsorption process. The investigation included examining the variations in removal efficiency at different pH levels and ZnCl2-RS doses. The characteristics of the ZnCl2-RS, prepared for the study, were determined through SEM and FTIR analyses, revealing a composition of 49.4% carbon and 8.3% zinc. At pH 5, the adsorption efficiency for DCF and PCM was enhanced, achieving removal rates of 92.2% for DCF and 89.1% for PCM with 0.2 g of ZnCl2-RS. The adsorption of DCF and PCM by ZnCl2-RS followed pseudo-second-order kinetic and adhered to the Langmuir isotherm model. The maximum adsorption capacities were calculated as 26.04 mg/g for DCF and 19.05 mg/g for PCM. In conclusion, the cost-effective production of activated carbon from agricultural waste like rice straw yielded a promising adsorbent material for efficiently removing pharmaceuticals such as diclofenac sodium and paracetamol. This approach not only contributes to waste reduction but also promotes the repurposing of agricultural waste materials.

Enhanced Photocatalytic Degradation by the Preparation of a Stable La-Doped FeTiO3 Photocatalyst: Experimental and DFT Study

The rapid photocarrier recombination limits the photocatalytic activity of iron titanate (FeTiO3) to be further improved. Developing novel approaches to inhibit the rapid recombination rate of the FeTiO3 photocatalysts is crucial for efficiently degrading pollutants in wastewater. Rare earth ions, with unique electron dispositions and large ion radii, could effectively inhibit photocarrier recombination. Herein, novel lanthanum (La)-doped FeTiO3 photocatalysts were designed and successfully synthesized. The photocatalytic performance of the 12 mol % La/FeTiO3 photocatalyst was superior in degrading tetracycline hydrochloride (TCH), methylene blue (MB), and brilliant blue (BB). These degradation rate constants (k) were 0.12358, 0.01357, and 0.03064 L mg-1 min-1, respectively, which were 12.83, 1.61, and 7.78 times that of pure FeTiO3. The photoelectronic tests and density functional theory (DFT) calculations revealed that the La 4f orbital forms an impurity energy level in the conduction band of FeTiO3. This level narrows the bandgap and acts as an electron acceptor, capturing photoexcited electrons and inhibiting the rapid recombination of photoexcited electron-hole pairs in FeTiO3. This work enhances the potential of FeTiO3 in the photocatalysis field and provides important insights into the efficient degradation of organic pollutants in wastewater.

Valorizing date palm spikelets into activated carbon-derived composite for methyl orange adsorption: advancing circular bioeconomy in wastewater treatment-a comprehensive study on its equilibrium, kinetics, thermodynamics, and mechanisms

Leveraging date palm spikelets (DPS) as a precursor, this study developed a DPS-derived composite (ZnO@DPS-AC) for water treatment, focusing on methyl orange (MO) removal. The composite was synthesized through ZnCl2 activation and pyrolysis at 600 °C. Comprehensive characterization was conducted using TGA, FTIR, XRD, SEM/EDS, and pHPZC. Characterization revealed a highly carbonaceous material (> 74% carbon) with significant porosity and surface functional groups. ZnO@DPS-AC demonstrated rapid MO removal, achieving over 45% reduction within 10 min and up to 99% efficiency under optimized conditions. The Langmuir model-calculated maximum adsorption capacity reached 226.81 mg/g at 20 °C. Adsorption mechanisms involved hydrogen bonding, π-π interactions, and pore filling. The composite showed effectiveness in treating real wastewater and removing other pollutants. This study highlights the potential of agricultural waste valorization in developing efficient, sustainable adsorbents for water remediation, contributing to circular bioeconomy principles.

Efficiency and mechanism of enhanced norfloxacin removal using amorphous TiO2-modified biochar

Inadequate treatment of antibiotic-contaminated wastewater, including compounds such as norfloxacin (NOR), poses a substantial treat to both ecological safety and human well-being. An innovative approach was devised to address NOR pollution using amorphous TiO2 modified biochar (A-TiO2/BC) prepared via sol-gel impregnation. The resultant had a commendably specific surface area of 131.8 m2/g-1, which was 1.91 times more than the original surface area of unmodified BC. A-TiO2/BC also exhibited abundant hydroxyl and oxygen-containing functional groups, thereby provided adequately active sites for NOR adsorption. R2 values obtained from NOR isotherm adsorption models descended in order of Freundlich < Temkin < Sips < Langmuir, which indicated that the NOR removal by A-TiO2/BC mainly complied with monolayer adsorption accompanied by heterogeneous surface adsorption. Under weakly acidic conditions, NOR adsorption benefits from the synergistic physicochemical interactions of A-TiO2 and BC. Notably, A-TiO2/BC demonstrated an impressive NOR adsorption capacity of up to 78.14 mg g-1, with a dosage of 20 mg L-1 at 25 °C under pH 6. Such A-TiO2 modified biochar thus presents a promising alternative for NOR removal.

Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field

N/S co-doping has emerged as a prevailing strategy for carbon-based adsorbents to facilitate the antibiotic removal efficiency. Nevertheless, the underlying interplay among N, S, and their adjacent vacancy defects remains overlooked. Herein, we present a novel in situ strategy for fabricating pyridinic-N dominated and S dual-doped porous carbon adsorbent with rich vacancy defects (VNSC). The experimental results revealed that N (acting as the electron donor) and S (acting as the electron acceptor) form an internal electric field (IEF), with a stronger IEF generated between pyridinic-N and S, while their adjacent vacancy defects activate carbon π electrons, thus enhancing the charge transfer of the IEF. Density functional theory (DFT) calculations further demonstrated that the rich charge transfer in the IEF facilitated the π-π electron donor-acceptor (EDA) interaction between VNSC and tetracycline (TC) as well as norfloxacin (NOR), and thus is the key to adsorption performance of VNSC. Consequently, VNSC exhibited high adsorption capacities toward TC (573.1 mg g-1) and NOR (517.0 mg g-1), and its potential for environmental applications was demonstrated by interference, environmentally relevant concentrations, fixed-bed column, and regeneration tests. This work discloses the natures of adsorption capacity for N/S dual-doped carbon-based materials for antibiotics.

Optimization of hydrothermal synthesis conditions of Bidens pilosa-derived NiFe2O4@AC for dye adsorption using response surface methodology and Box-Behnken design

The presence of stable and hazardous organic dyes in industrial effluents poses significant risks to both public health and the environment. Activated carbons and biochars are widely used adsorbents for removal of these pollutants, but they often have several disadvantages such as poor recoverability and inseparability from water in the post-adsorption process. Incorporating a magnetic component into activated carbons can address these drawbacks. This study aims to optimizing the production of NiFe2O4-loaded activated carbon (NiFe2O4@AC) derived from a Bidens pilosa biomass source through a hydrothermal method for the adsorption of Rhodamine B (RhB), methyl orange (MO), and methyl red (MR) dyes. Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to analyze the key synthesis factors such as NiFe2O4 loading percentage (10-50%), hydrothermal temperature (120-180 °C), and reaction time (6-18 h). The optimized condition was found at a NiFe2O4 loading of 19.93%, a temperature of 135.55 °C, and a reaction time of 16.54 h. The optimum NiFe2O4@AC demonstrated excellent sorption efficiencies of higher than 92.98-97.10% against all three dyes. This adsorbent was characterized, exhibiting a well-developed porous structure with a high surface area of 973.5 m2 g-1. Kinetic and isotherm were studied with the best fit of pseudo-second-order, and Freundlich or Temkin. Qmax values were determined to be 204.07, 266.16, and 177.70 mg g-1 for RhB, MO, and MR, respectively. By selecting HCl as an elution, NiFe2O4@AC could be efficiently reused for at least 4 cycles. Thus, the Bidens pilosa-derived NiFe2O4@AC can be a promising material for effective and recyclable removal of dye pollutants from wastewater.

Important role of pore-filling mechanism in separating naproxen from water by micro-mesoporous carbonaceous material

Commercial micro-mesoporous carbonaceous material (MCM; 56.8% mesopores) was applied for investigating the removal phenomenon of naproxen drug in aqueous solutions through batch adsorption experiments. Results demonstrated that the adsorption capacity of MCM to naproxen was slightly affected by different pHeq (2.0-11) and ionic strength (0-1 M NaCl). Adsorption kinetics, isotherms, thermodynamics, and mechanisms were evaluated at pH 7.0. Adsorption kinetics indicated the rate constants for adsorption (0.2 × 10-3  L/(mg × min) and desorption (0.076/min) and the adsorption equilibrium constant (2.6 × 10-3  L/mg). Adsorption isotherm showed that MCM exhibited a high-affinity adsorption capacity to naproxen (even at low concentrations) and its Langmuir maximum adsorption capacity (Qmax ) was 252.7 mg/g at 25°C. Adsorption thermodynamics proved that the adsorption process was endothermic and physisorption (ΔH° = 9.66 kJ/mol). The analysis result of pore size distribution demonstrated that the internal pore structure of MCM was appropriate for adsorbing naproxen molecules. Pore-filing mechanism (pore diffusion phenomenon) was confirmed by a considerable decrease in BET-surface area (585 m2 /g) and total pore volume (0.417 cm3 /g) of MCM after adsorbing naproxen (~1000 mg/L and pH 7.0) at 5 min (341 and 0.256), 60 min (191 and 0.205), 120 min (183 and 0.193), 360 min (144 and 0.175), and 24 h (71.6 m2 /g and 0.123 cm3 /g, respectively). The pore diffusion occurred rapidly (even at the initial adsorption period of 5 min). The FTIR technique was applied to identify the existence of C-H···π and n-π interaction. π-π interaction (evaluated through ID /IG ratio and C=C band) played a minor contribution in adsorption mechanisms. The ID /IG ratio (determined by the Raman technique) of MCM before adsorption (1.195) was similar to that after adsorption (1.190), and the wavenumber (C=C band; its FTIR spectrum) slightly shifted from 1638 to 1634 cm-1 after adsorption. A decrease in the Qmax value of MCM from 249 to 217 (H2 O2 -oxidized MCM) or to 224 mg/g (HNO3 -oxidized MCM) confirmed the presence of π-π interaction. Electrostatic attraction was a minor contribution. MCM can serve as a promising material for removing naproxen from water environment through a pore-filling mechanism. PRACTITIONER POINTS: Pore-filling mechanism was proposed by comparing textural properties of MCM before and after adsorbing naproxen. C-H···π and n-π interactions were identified via FTIR technique. π-π interaction was observed by FTIR and Raman techniques. Oxidation of MCM with HNO3 or H2 O2 was a helpful method to explore π-π interaction. Electrostatic attraction was explained through studies: effects of pH and NaCl along with desorption.

Removal of benzotriazole derivatives by biochar: Potential environmental applications

Benzotriazole and its derivatives (BTAs) are commonly present in wastewater due to their extensive use in industrial processes, yet their removal is still unexplored. Here, we test the removal of these pollutants using two functionalised biochars, synthesised from wild plum (WpOH) and apricot (AsPhA) kernels. The aim of this work was to optimise the adsorption process against various BTAs (i.e., benzotriazole (BTZ), 4-hydroxy-1H-benzotriazole (OHBZ), 4-methyl-1H-benzotriazole (4 MBZ), 5-methyl-1H-benzotriazole (5 MBZ), 5-chloro-1H-benzotriazole (ClBZ), 5,6-dimethyl-1H-benzotriazole (DMBZ)), and determine the adsorption mechanisms at play, using real wastewater matrices. Batch studies showed that the optimal adsorption pH ranged between 4 and 6 for WpOH and AsPhA, respectively, and equilibrium was reached after 240 min. The kinetic models that best described the adsorption process were in the following order: Elovich model > pseudo-second order model > pseudo-first order model. The equilibrium data showed the highest correlation with the Freundlich isotherm, indicating multilayer adsorption. The maximum adsorption capacity obtained in mixtures was 379 mg/g on WpOH and 526 mg/g on AsPhA. The mechanistic work revealed that the BTAs became bound to the biochar primarily through H-bonding, n-π and π-π EDA interactions. In wastewater, obtained before and after conventional treatment, the concentration of OHBZ and BTZ was reduced by >40%, while the concentration of the other compounds studied fell below the detection limit (∼2.0-90 ng/L). Finally, using a Vibrio fischeri assay, we showed that adsorption onto AsPhA significantly reduced the relative toxicity of both raw and treated wastewater.

Hydrothermal Pretreatment of KOH for the Preparation of PAC and Its Adsorption on TC

The environment has been heavily contaminated with tetracycline (TC) due to its excessive use; however, activated carbon possessing well-developed pores can effectively adsorb TC. This study synthesized pinecone-derived activated carbon (PAC) with high specific surface area (1744.659 cm²/g, 1688.427 cm²/g) and high adsorption properties (840.62 mg/g, 827.33 mg/g) via hydrothermal pretreatment methods utilizing pinecones as precursors. The results showed that PAC treated with 6% KOH solution had excellent adsorption properties. It is found that the adsorption process accords with the PSO model, and a large amount of C=C in PAC provides the carrier for π-πEDA interaction. The results of characterization and the isothermal model show that TC plays a key role in the adsorption process of PAC. It is concluded that the adsorption process of TC on PAC prepared by hydrothermal pretreatment is mainly pore filling and π-πEDA interaction, which makes it a promising adsorbent for TC adsorption.

Iron-engineered mesoporous biocarbon composite and its adsorption, activation, and regeneration approach for removal of paracetamol in water

Three-dimensional multi-porous Iron Oxide/carbon (Fe₂O₃/C) composites derived from tamarind shell biomass were synthesized by a single-step co-pyrolysis technique and utilized for Paracetamol (PAC) dismissal in the combined adsorption, and advanced oxidation such as electrochemical regeneration techniques. The Fe₂O₃/C composites were prepared by different pyrolysis temperatures, and named as TS750 (without Fe₂O₃at 750 °C), MTS450 BCs (Low-450 °C), MTS600 BCs (Moderate-600 °C) and MTS750 BCs (high-750 °C), respectively. As-prepared Fe₂O₃/C composite was characterized by FE-SEM, XRD, BET, and XPS analysis. The specific surface area and the spatial interaction between the interlayers of Fe₂O₃ and C were significantly improved by increasing the pyrolysis temperatures from 450 to 750 °C, which improved the adsorption capacity of Fe₂O₃/C composites in terms of higher rate constants and chemisorption kinetics. The Pseudo-second-order kinetics model fitted in the adsorption test results of Fe₂O₃/C composites with the highest correlation co-efficiency. The Langmuir-isotherms model fitted in the adsorption test of the TS750 and MTS450 BCs. The Freundlich isotherms model is more fit with MTS600 and MTS750 BCs. Based on the isotherm results, the MTS750 BCs achieved 46.9 mg/g of maximum PAC adsorption capacity. The optimized MTS750 composites could be completely recovered by using an advanced electrochemical oxidation regeneration approach within 180 min. Also, with the adsorption and recovery process, the TOC removal rate improved to ∼79.4%. After the 6th cycle electrochemical oxidation process, the obtained results of the re-adsorption test showed the stabile adsorption activity of the sorbent material. The data outcomes herein propose that this type of combined adsorption and electrochemical approach will be useful in commercial water treatment plants.

Mechanisms of polystyrene nanoplastics adsorption onto activated carbon modified by ZnCl2

In this study, the adsorption capacity of activated carbon was enhanced after zinc chloride activation. The effects of pore filling, n-π and π-π interaction and electrostatic interaction on the adsorption of polystyrene nanoplastics (PSNPs) by activated carbon were determined by SEM, BET, Raman spectrum, FTIR and surface Zeta potential. Pore filling, electrostatic interaction and n-π interaction and π-π interaction all played a role in the adsorption process, but n-π interaction and π-π interaction was not the decisive role. The adsorption of PSNPs on activated carbon conformed to the pseudo-second-order kinetics and Langmuir isotherm, and there was spontaneous physical adsorption process driven by entropy in the adsorption process. Further, the effects of common anions SO₄^2-, HCO₃^-, and Cl^- in water on the adsorption of PSNPs by activated carbon were investigated, and the results showed that the presence of these ions could increase the adsorption capacity to some extent. ZCAC has a stable adsorption capacity under tap water, but its adsorption capacity is affected under lake water. In addition, the reuse of activated carbon was investugated, and the adsorption capacity of activated carbon was fully recovered after high temperature calcination. This study provided a direction for materials modification of adsorbed nanoplastics and a feasible method for removal of nanoplastics in drinking water treatment plants.