Synthesis and Characterization of Novel Hybridized CeO2@SiO2 Nanoparticles Based on Rice Husk and Their Application in Antibiotic Removal

Removal of N-Nitrosodiphenylamine from contaminated water: A novel modeling framework using metaheuristic-based ensemble models

Investigating the complex interactions among physicochemical variables that influence the adsorptive removal of pollutants is a challenge for conventional one-variable-at-a-time (OVAT) batch methods. The adoption of machine learning-based chemometric prediction models is expected to be more accurate than the conventional method. This study proposed a novel modeling framework for predicting and optimizing the adsorptive removal of N-Nitrosodiphenylamine (NDPhA). Initially, models were trained by using OVAT data, with their hyperparameters subsequently fine-tuned through Bayesian optimization. In the second phase, the particle swarm optimization (PSO) technique was adopted to identify optimal parameters, specifically time, concentration, temperature, pH, and dose, to ensure the highest removal. The adopted analytical method enhances both prediction accuracy and removal efficiency. Utilizing OVAT data for NDPhA removal, the XGBoost regressor significantly outperformed other models. With a correlation coefficient of 0.9667 in the testing dataset, the XGBoost model exhibited its accuracy, emphasized by its low mean squared errors of 28.45 and mean absolute errors of 0.0982. Feature importance analysis consistently identified time and concentration as the most critical factors across all models.

Performance of magnetic nanocomposite based on xanthan gum-grafted-poly(acrylamide) crosslinked by borax for the effective elimination of amoxicillin from aquatic environments

This study evaluated the effectiveness of using nanocomposite (NCs) of xanthan gum grafted polyacrylamide crosslinked Borax - iron oxide nanoparticle (XG-g-pAAm-CL-Borax-IONP) to remove the amoxicillin antibiotic (AMX) from an aquatic environment. To confirm the structural characteristics of the prepared XG-g-pAAm-CL-Borax-IONP NCs, unique characterization methods (XRD, FT-IR, FE-SEM, EDX, BET, TGA, Zeta, and VSM) were used. Adsorption experimental setups were performed with the influence of solution pH (4-9), the effect of adsorbent dose (0.003-0.02 g), the effect of contact time (5-45 min), and the effect of initial AMX concentration (50-400 mg/L) to achieve the most efficient adsorption conditions. Based on the Freundlich isotherm model, XG-g-pAAm-CL-Borax-IONP NCs provided the maximum AMX adsorption capacity of 1183.639 mg/g. This research on adsorption kinetics also established that the pseudo-second-order model (R2 = 0.991) is outstanding compatibility with the experimental results. AMX adsorption on the NCs may occur through intermolecular hydrogen bonding, diffusion, and trapping into the polymer network. Even after five cycles, these NCs still displayed the best performance. Based on these results, XG-g-pAAm-CL-Borax-IONP NCs may be a viable material for the purification of AMX from contaminated water.

Highly Adsorptive Removal of Ciprofloxacin and E.coli inactivation using Amino acid Tryptophan Modified Nano-gibbsite

Adsorption of essential amino acid, Tryptophan (Tryp) on synthesized gibbsite nanoparticles and their applications in eliminating of antibiotic ciprofloxacin (CFX) and bacteria Escherichia coli (E.coli) in aqueous solution. Nano-gibbsite which was successfully fabricated, was characterized by XRD, TEM-SAED, FT-IR, SEM-EDX and zeta potential measurements. The selected parameters for Tryp adsorption on nano-gibbsite to form biomaterial, Tryp/gibbsite were pH 11, gibbsite dosage 20 mg/mL and 1400 mg/L Tryp. The optimum conditions for CFX removal using Tryp/gibbsite were adsorption time 60 min, pH 5, and 20 mg/mL Tryp/gibbsite dosage. The CFX removal significantly raised from 63 to 90% when using Tryp/gibbsite. The Freundlich and pseudo-second-order models achieved the best fits for CFX adsorption isotherm and kinetic on Tryp/gibbsite, respectively. The amount of CFX increased with increasing ionic strength, suggesting that both electrostatic and non-electrostatic interactions were important. After four reused time, CFX removal was greater than 66%, demonstrating that Tryp/gibbsite is reusable with high performance in removing CFX. The application in bacterial activity in term of E.coli reached greater than 98% that was the best material for bacteria inactivation. The present study reveals that Tryp/gibbsite is an excellent bio-material for removing CFX and E.coli.

Machine-Learning-Assisted Aggregation-Induced Emissive Nanosilicon-Based Sensor Array for Point-of-Care Identification of Multiple Foodborne Pathogens

How timely identification and determination of pathogen species in pathogen-contaminated foods are responsible for rapid and accurate treatments for food safety accidents. Herein, we synthesize four aggregation-induced emissive nanosilicons with different surface potentials and hydrophobicities by encapsulating four tetraphenylethylene derivatives differing in functional groups. The prepared nanosilicons are utilized as receptors to develop a nanosensor array according to their distinctive interactions with pathogens for the rapid and simultaneous discrimination of pathogens. By coupling with machine-learning algorithms, the proposed nanosensor array achieves high performance in identifying eight pathogens within 1 h with high overall accuracy (93.75-100%). Meanwhile, Cronobacter sakazakii and Listeria monocytogenes are taken as model bacteria for the quantitative evaluation of the developed nanosensor array, which can successfully distinguish the concentration of C. sakazakii and L. monocytogenes at more than 103 and 102 CFU mL-1, respectively, and their mixed samples at 105 CFU mL-1 through the artificial neural network. Moreover, eight pathogens at 1 × 104 CFU mL-1 in milk can be successfully identified by the developed nanosensor array, indicating its feasibility in monitoring food hazards.

Static adsorption and photocatalytic degradation of amoxicillin using titanium dioxide/hydroxyapatite nanoparticles based on sea scallop shells

The objective of this study is to investigate the efficiency of two processes for the amoxicillin removal through static (batch) adsorption and photocatalytic degradation onto the prepared samples. Three solid materials as photocatalyst and/or adsorbent were synthesized viz. nanotitanium dioxide (NT) prepared by the sol-gel method, scallop shells-based nanohydroxyapatite (NP), and nanotitanium dioxide/nanohydroxyapatite composite (NTP). The physicochemical and morphological properties of the prepared samples were tested by TGA, XRD, DRS, ATR-FTIR, nitrogen adsorption/desorption isotherm, zeta potential, SEM, and TEM. The major operational conditions were optimized for catalyst or adsorbent mass, pH, shaking time, initial amoxicillin (AMX) concentration, power of UV lamp, and temperature. The results illuminated that NTP achieved the highest adsorption capacity (88.46 mg/g) at 20 ℃ and AMX adsorption onto all the solid materials was well applied by Langmuir, Temkin, pseudo-second order, and Elovich models. The maximum desorption percent (98%) was attained by acetone. The degradation percent of AMX reached 85.3 and 99.5% for NT and NTP, respectively, using 0.9 g/L of catalyst dosage through 90 min. AMX photodegradation onto the catalysts' surface was well fitted by Langmuir-Hinshelwood, Arrhenius, and Eyring-Polanyi models with endothermic, physical, and nonspontaneous nature of photocatalysis process. NTP acts as a promising adsorbent and photocatalyst for the antibiotics' removal in wastewater.

Metal organic framework-derived recyclable magnetic coral Co@Co3O4/C for adsorptive removal of antibiotics from wastewater

The menace posed by antibiotic contamination to humanity has increased due to the absence of efficient antibiotic removal processes in the conventional waste water treatment methods from the hospitals, households, animal husbandry, and pharma industry. Importantly, only a few commercially available adsorbents are magnetic, porous, and have the ability to selectively bind and separate various classes of antibiotics from the slurries. Herein, we report the synthesis of a coral-like Co@Co3O4/C nanohybrid for the remediation of three different classes of antibiotics - quinolone, tetracycline, and sulphonamide. The coral like Co@Co3O4/C materials are synthesized via a facile room temperature wet chemical method followed by annealing in a controlled atmosphere. The materials demonstrate an attractive porous structure with an excellent surface-to-mass ratio of 554.8 m2 g-1 alongside superior magnetic responses. A time-varying adsorption study of aqueous nalidixic acid solution on Co@Co3O4/C nanohybrids indicates that these coral-like Co@Co3O4/C nanohybrids could achieve a high removal efficiency of 99.98% at pH 6 in 120 min. The adsorption kinetics data of Co@Co3O4/C nanohybrids follow a pseudo-second-order reaction kinetics suggesting a chemisorption effect. The adsorbent has also shown its merit in reusability for four adsorption-desorption cycles without showing significant change in the removal efficiency. More in-depth studies validate that the excellent adsorption capability of Co@Co3O4/C adsorbent attributing to the electrostatic and π-π interaction between adsorbent and various antibiotics. Concisely, the adsorbent manifests the potential for the removal of a wide range of antibiotics from the water alongside showing their utility in the hassle-free magnetic separation.

Mussel-inspired magnetic adsorbent MnO2/PDA@Fe3O4 for removing heavy metal ions contaminants in single and mixed systems

Heavy metal pollution has been a magnificent concern for a long period. A novel magnetic material, MnO₂/PDA@Fe₃O₄, was prepared in this paper. With the assistance of multiple characterization methods, it was confirmed that polydopamine coated the magnetic nucleus and acted as a dense intermediate layer for MnO₂ attachment. Having superior adsorption performance, MnO₂/PDA@Fe₃O₄ could remove heavy metal cations efficiently no matter in single or mixed systems. The maximum adsorption capacities calculated by the Langmuir model for Pb(II), Cu(II), and Cd(II) were 295.01 mg/g, 130.30 mg/g, and 115.16 mg/g, respectively. In mixed systems, the adsorbent showed obvious selectivity for Pb(II). And the variation of Cu(II) concentration was more responsible for Pb(II) adsorption than that of Cd(II). The kinetic and thermodynamic data revealed that the polluted ions immobilizations by MnO₂/PDA@Fe₃O₄ were chemisorption and were endothermic, entropy increase, spontaneous process. The presence of humic acid and coexisting ions induced only a very limited interference. In addition, MnO₂/PDA@Fe₃O₄ maintained excellent adsorption performance and stability after five cycles of adsorption and removed 98.33% Pb(II) and 71.24% Cu(II) from actual water, respectively. This study confirmed that the MnO₂/PDA@Fe₃O₄ had great potential and broad prospects to remediate the heavy metal contaminants in water.

Adsorptive removal of dichlorophenoxyacetic acid (2,4-D) using novel nanoparticles based on cationic surfactant-coated titania nanoparticles

A novel nanomaterial based on cationic surfactant-coated TiO₂ nanoparticle (CCTN) was systematically fabricated in this work. Synthesized titania nanoparticles were thoroughly characterized by XRD, FT-IR, HR-TEM, TEM-EDX, SEM with EDX mapping, BET, and ζ potential measurements. The adsorption of cationic surfactant, cetyltrimethylammonium bromide (CTAB), on TiO₂ was studied under various pH and ionic strength conditions. Adsorption of CTAB on TiO₂ increased with ionic strength increment in the presence of hemimicelle monolayer structure, indicating that nonelectrostatic and electrostatic forces control CTAB uptake. CTAB adsorption isotherms on TiO₂ were according to a two-step model. Potential application in pesticide removal of 2,4-dichorophenoxy acetic acid (2,4-D) using CCTN was also studied. Optimum parameters for 2,4-D treatment through adsorption technique were pH 5, adsorption time of 120 min, and CCTN dosage of 10 mg·mL^-1. Very low 2,4-D removal efficiency using TiO₂ without CTAB coating was found to be approximately 28.5% whereas the removal efficiency was up to about 90% by using CCTN under optimum conditions, and the maximum adsorption capacity of 12.79 mg·g^-1 was found. Adsorption isotherms of 2,4-D on CCTN were more suitable with the Langmuir model than Freundlich. Adsorption mechanisms of 2,4-D on CCTN were mainly governed by Columbic attraction based on isotherms and surface charge changes.

Efficient and recyclable degradation of organic dye pollutants by CeO2@ZIF-8 nanozyme-based non-photocatalytic system

Advanced oxidation processes-based catalysis system as the most typical pollutant degradation technology always suffer from poor durability and photo-dependent. Inspired by the fact that some nanomaterials exhibit catalytic properties closer to natural enzymes, a high peroxidase-like activity and stability CeO₂@ZIF-8 nanozyme was synthesized in this study for non-photodegradation of dyes pollution. Multiple characterization techniques were applied to prove the successful synthesis of the nanozyme. The influence of different parameters on the catalytic degradation of organic dye by nanozyme was investigated. This nanozyme achieved a maximum degradation efficiency of 99.81% for methyl orange and maintained its catalytic performance in repeated experiments. Possible degradation intermediates and pathways for methyl orange were then proposed. In addition, the CeO₂@ZIF-8 loaded starch/agarose films were prepared for the portable and recyclable remediation of real dye wastewater, which maintained more than 80% degradation efficiency after 5 successive cycles. These results suggested that nanozyme based non-photocatalytic system is a potential catalyst for dye degradation and it opens a new avenue to develop high-performance and recyclable catalysts for pollutant remediation.

Process optimization for enhanced carbon capture and cyclic stability using adsorbents derived from coal fly ash

Zeolites and metal-organic frameworks (MOFs) are popular adsorbents when it comes to capturing CO₂ from the gaseous feed stream. In this study, a hybrid of zeolite and ZIF-8 adsorbent was synthesized from coal fly ash via fusion-hydrothermal process and then in-situ aqueous ZIF-8 synthesis technique. This technique of in-situ synthesis is highly cost-effective as it is done at room temperature. The hybrid adsorbent showed an enhanced microporosity as compared to zeolites synthesized from coal fly ash due to the in-situ synthesis of ZIF-8 upon coal fly ash zeolite. It was designated as CFAZ/ZIF-8. At 298 K, a maximum CO₂ uptake value of 2.83 mmol/g was observed with a constant decrease with an increase in temperature. BET surface area value of 426 m²/g was obtained for this adsorbent. Kinetics fit for the best uptake value was performed with the Avrami model kinetics, describing the adsorption well at an R² value of 0.997 for the fit. The adsorbent also showed impressive cyclic stability after five cycles of carbonation and decarbonation. The cyclic stability studies show that the as-synthesized hybrid adsorbent shows promise in CO₂ uptake studies.

Adsorption performance and mechanism of cationic and anionic dyes by KOH activated biochar derived from medical waste pyrolysis

The massive generation of medical waste (MW) results in a series of environmental, social, and ecological problems. Pyrolysis is one such approach that has attracted more attention because of the production of value-added products with lesser environmental risk. In this study, the activated biochar (ABC600) was obtained from MW pyrolysis and activated with KOH. The adsorption mechanism of activated biochar on cationic (methylene blue) and anionic (reactive yellow) dyes were studied. The physicochemical characterization of biochar showed that increasing pyrolysis temperature and KOH activation resulted in increased surface area, a rough surface with a clear porous structure, and sufficient functional groups. MB and RYD-145 adsorption on ABC600 was more consistent with Langmuir isotherm (R² ≥ 0.996) and pseudo-second-order kinetics (R² ≥ 0.998), indicating chemisorption with monolayer characteristics. The Langmuir model fitting demonstrated that MB and RYD-145 had maximum uptake capacities of 922.2 and 343.4 mg⋅g^-1. The thermodynamics study of both dyes showed a positive change in enthalpy (ΔH°) and entropy (ΔS°), revealing the endothermic adsorption behavior and randomness in dye molecule arrangement on activated-biochar/solution surface. The activated biochar has excellent adsorption potential for cationic and anionic dyes; hence, it can be considered an economical and efficient adsorbent.

Synthesis and Characterization of Novel Core-Shell ZnO@SiO2 Nanoparticles and Application in Antibiotic and Bacteria Removal

A novel core-shell nanomaterial, ZnO@SiO₂, based on rice husk for antibiotic and bacteria removal, was successfully fabricated. The ZnO@SiO₂ nanoparticles were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), Brunauer-Emmett-Teller (BET) method, diffuse reflectance ultraviolet-vis (DR-UV-vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and ζ-potential measurements. β-Lactam antibiotic amoxicillin (AMX) was removed using ZnO@SiO₂ nanoparticles with an efficiency greater than 90%, while Escherichia coli removal was higher than 91%. The optimum effective conditions for AMX removal using ZnO@SiO₂, including solution pH, adsorption time, and ZnO@SiO₂ dosage, were 8, 90 min, and 25 mg/mL, respectively. The maximum adsorption capacity reached 52.1 mg/g, much higher than those for other adsorbents. Adsorption isotherms of AMX on ZnO@SiO₂ were more in accordance with the Freundlich model than the Langmuir model. The electrostatic attraction between negative species of AMX and the positively charged ZnO@SiO₂ surface induced adsorption, while the removal of E. coli was governed by both electrostatic and hydrophobic interactions. Our study demonstrates that ZnO@SiO₂ based on rice husk is a useful core-shell nanomaterial for antibiotic and bacteria removal from water.

Highly adsorptive protein inorganic nanohybrid of Moringa seeds protein and rice husk nanosilica for effective adsorption of pharmaceutical contaminants

The present study aims to investigate adsorption characteristics and mechanisms of Moringa (MO) seeds protein on nanosilica rice husk and their applications in removal of pharmaceutical residues including the fluoroquinolone antibiotic levofloxacin (LFX) and the nonsteroidal anti-inflammatory drug diclofenac (DCF) in aquatic environment. Molecular weight of MO protein was determined by gel-permeation chromatography (GPC) method while its amino acids were quantified by high performance liquid chromatography (HPLC). The number-(M_n) and weight-average molecular weights (M_w) of MO protein were 1.53 × 10⁴ and 1.61 × 10⁴ g/mol, respectively. Different effective conditions on adsorption protein on nanosilica including contact time, pH, adsorbent dosage, and ionic strength were systematically optimized and found to be 180 min, 10, 10 mg/mL and 1 mM KCl, respectively. The surface charge change by zeta potential, surface modification by Fourier-transform infrared spectroscopy (FT-IR) and adsorption isotherms demonstrated that protein adsorption on nanosilica was governed by both electrostatic and non-electrostatic interactions. Application of protein functionalized nanosilica (ProFNS) in LFX and DCF removal were also thoroughly studied. The selected conditions for LFX and DCF removal using ProFNS were 1 mM KCl for both LFX and DCF; pH 8 and pH 6; contact time 90 and 120 min, and adsorption dosage 10 and 5 mg/ml for LFX and DCF, respectively. Adsorption isotherms of protein on nanosilica as well as LFX and DCF onto ProFNS at different ionic strengths were reasonably fitted by the two-step model while a pseudo-second-order model could fit adsorption kinetic well. The removal of LFX and DCF using ProFNS significantly increased from 51.51% to 87.35%, and 7.97%-50.02%, respectively. High adsorption capacities of 75.75 mg/g for LFX and 59.52 mg/g for DCF, indicate that ProFNS is a great performance for pharmaceutical residues removal in water environment.

Reducing the negative impact of ceftriaxone and doxycycline in aqueous solutions using ferrihydrite/plant-based composites: mechanism pathway

The adsorption of ceftriaxone (CET) and doxycycline (DOX) from aqueous solution using ferrihydrite/plant-based composites (silica rice husk) to reduce their negative impact on the ecosystem was adequately studied. On the other hand, phosphate and humic acid are often found in water and soil; in view of this, their effects on the adsorption of CET and DOX were investigated. The results showed that the removal of ceftriaxone decreased with an increase in pH, while that of doxycycline did not. Ferrihydrite with 10% silica rice husk (Fh-10%SRH) has the highest maximum adsorption capacity of 139 and 178 mg g^-1 for CET and DOX, respectively, at room temperature based on Liu's adsorption isotherm. This implies that the presence of silica rice husk increases CET and DOX uptake due to an increase in the pore volume of FH-10%SRH. The results showed that phosphate had a significant inhibition role on CET adsorption and minor on DOX, whereas humic acid salt affected neither case. Increase in temperature up to 333 K favored the adsorption of both contaminants. The proposed adsorption mechanisms of ceftriaxone are electrostatic interaction, n-π interaction, and hydrogen bond, while that of DOX entails n-π interaction and hydrogen bond.

Recent Progress in Research of Solid Tritium Breeder Materials Li2TiO3: A Review

During the past decades, fusion reactor fuels such as deuterium and tritium have been extensively investigated due to increasing interest in nuclear fusion energy. Tritium, which is scarce in nature, needs to be fabricated by tritium breeder materials. Among the commonly investigated tritium breeder materials, lithium titanate (Li2TiO3) is recognized as one of the most promising solid tritium breeder materials because of its considerable lithium (Li) atomic density, low activation, excellent chemical stability, and low-temperature tritium release performance. This paper aims to provide a systematic review of the current progress in Li2TiO3 preparation methods as well as the high Li density, tritium release performance, irradiation behavior, and modification technologies of Li2TiO3 pebbles. Li2TiO3 can be synthesized by strategies such as solid-state, sol–gel, hydrothermal, solution combustion synthesis, and co-precipitation methods. Among them, the hydrothermal method is promising due to its simplicity and low cost. Many researchers have begun to focus on composite ceramic pebbles to further improve tritium breeder performance. This will provide a new direction for the future development of Li2TiO3 pebbles. The present review concludes with a summary of the preparation methods currently under development and offers an outlook of future opportunities, which will inspire more in-depth investigation and promote the practical application of Li2TiO3 in this field.

Removal of beta-lactam antibiotic in water environment by adsorption technique using cationic surfactant functionalized nanosilica rice husk

This study aims to investigate the adsorption characteristics of cationic surfactant, cetyltrimethylamonium bromide (CTAB) onto negatively nanosilica rice husk surface and the application for antibiotic treatment in water environment. Adsorption of CTAB onto nanosilica increased with an increase of solution pH, due to an enhancement of the electrostatic attraction between cationic methylamomethylamonium groups and negatively charged nanosilica surface enhanced at higher pH. Adsorption of CTAB decreased with a decrease of ionic strength while a common intersection point (CIP) was observed for adsorption isotherm at different ionic strengths, suggesting that hydrophobic interactions between alkyl chains in CTAB molecules significantly induced adsorption and admicelles with bilayer formation were dominant than monolayer of hemimicelles. The CTAB functionalized nanosilica (CFNS) was applied for removal of beta-lactam amoxicillin (AMX). The best conditions for AMX treatment using CFNS were selected as pH 10, contact time 60 min and CFNS dosage 10 mg/mL. Removal efficiency of AMX using CFNS reached to 100% under optimum conditions while it was only 25.01% using nanosilica without CTAB. The maximum AMX adsorption capacity using CFNS of about 25 mg/g was much higher than other adsorbents. The effects of different organics such as humic acid, anionic surfactant, and other antibiotics on AMX removal using CFNS were also studied. A two-step model can fit CTAB uptake isotherms onto nanosilica and AMX onto CFNS well at different KCl concentrations. Based on the desorption of CTAB with AMX adsorption as well as adsorption isotherms, the change in surface charge and functional vibration groups after adsorption, we indicate that AMX adsorption onto CFNS was mainly controlled by electrostatic interaction. We reveal that CFNS is an excellent adsorbent for antibiotic treatment from aqueous solution.

Heat and ZnCl2 chemical carbonization of date stone as an adsorbent: optimization of material fabrication parameters and adsorption studies

In the present study, the optimization of factors for the fabrication of highly adsorptive activated carbon from agricultural waste (date stone) was investigated by using ZnCl₂ as a chemical agent during the heat treatment. ZnCl₂ acts as a dehydration agent during the heat treatment, allowing a better porosity. In addition, it boosts the fragmentation of the lignocellulosic structure and the condensation of carbon rings. The findings of this investigation showed that the synthesis conditions for better ZnCl₂ chemical/heat carbonization to fabricate an adsorbent from date stone are 700 °C, 120 min, and 2.0 g/g. The characterization analysis showed that the as-prepared activated carbon exhibits a surface area of 1036 m²/g, an iodine number of 928.5 mg/g, and phenol number of 2.1 mmol/g, which are comparable to commercial activated carbons. Batch sorption tests to remove methylene blue (MB) from water showed a maximum adsorption capacity of 384.6 mg/g using the prepared activated carbon. Equilibrium data was best fitted by the Langmuir isotherm model. It was found also that the kinetic adsorption data obeyed the pseudo-first order, and both external diffusion and intra-particle diffusion control the adsorption. Based on the obtained results, the optimization of synthesis conditions may help the transfer of technology in terms of agriculture-based material valorization towards the environmental remediation.

Efficient with low-cost removal and adsorption mechanisms of norfloxacin, ciprofloxacin and ofloxacin on modified thermal kaolin: experimental and theoretical studies

Quinolone antibiotics (QNs) can be potential hazard to environment and human. Combination of experimental and theoretical studies was used to analyze the adsorption properties of norfloxacin, ciprofloxacin and ofloxacin on modified thermally activated kaolin (KL). Main factors (calcination temperature, dose, pH, cations and regeneration) affecting the adsorption were discussed. Adsorption processes fit the pseudo-second order kinetic and Langmuir model well. The adsorption removal of norfloxacin, ciprofloxacin and ofloxacin can reach 88.53%, 89.43% and 91.46%, respectively. Cations inhibited adsorption, and AlS-KLB can maintain 80% efficiency in five cycles under optimal conditions. Simulations showed that the materials had good adsorption capacity for QNs, and the "①" of KL had the best capacity. Simulations explain the adsorption mechanism: F, H, O atoms of QNs are covalently bonded to O atoms from KL, Al₂O₃ and Al (OH)₃, C atoms from amorphous carbon and H atoms from C-H and Al (OH)₃. The Al atoms of Al₂O₃ and Al, Si atoms of KL are ionically bonded to F, H, O atoms of QNs. This study shed new light on the removal of QNs by providing low-cost and efficient modified KL and elucidating the adsorption mechanism in conjunction with DFT simulations.

Chemical Vapor Deposition Growth of MoS2 on g-C3N4 Nanosheets for Efficient Removal of Tetracycline Hydrochloride

MoS₂ was vertically grown on g-C₃N₄ nanosheets by chemical vapor deposition to prepare nanocomposites named MS-CN samples. Because of a large-surface area of 545.2 m²·g^-1 and a total pore volume of 1.7 cm³·g^-1, the sample MS-CN revealed fast and large adsorption capacity for tetracycline hydrochloride (TCH). The adsorption kinetics model proved that TCH could be rapidly adsorbed within 5 min, and chemical adsorption was dominant. For single-component adsorption of TCH, the maximum adsorption capacity was ∼154 mg/g. The monolayer adsorption was carried out on the surface of MS-CN. Both of the film and intra-particle diffusion were considered as significant processes to facilitate adsorption. Thermodynamic parameters indicate that the adsorption of TCH is a spontaneous endothermic process. The adsorption of TCH was highly pH-dependent. The maximum adsorption capacity of TCH was obtained in the case of pH ∼ 7. After four adsorption and desorption cycles, MS-CN still maintained well-adsorption performance. Multiple adsorption mechanism, pore filling, electrostatic force, π-π conjugation, and hydrogen bonding interactions were studied. Because of fast adsorption, large adsorption capacity, and high stability, it is a promising adsorbent for antibiotics.

Porous Aluminum-Based Metal-Organic Framework-Aminoclay Nanocomposite: Sustainable Synthesis and Ultrahigh Sorption of Cephalosporin Antibiotics

A novel sorbent was synthesized based on MIL-53(Al) MOF grown over an aminoclay (AC) platform, called MIL-53(Al)@AC nanocomposite, via a green and facile hydrothermal method. The nanocomposite was characterized using FT-IR, PXRD, BET, TEM, FESEM, EDS, XPS, TGA, DLS, and zeta potential analyses. BET analysis represented the porous nature and great surface area of MIL-53(Al)@AC. The high crystalline structure for the synthesized nanocomposite was verified using the PXRD pattern. FESEM, EDS, TEM, and XPS analysis proved the successful decoration of MIL-53(Al) over the AC platform. Cephalosporin antibiotics cefixime (CFX) and cephalexin (CPX), which are often present in wastewaters, were utilized to examine the sorption capacity of the nanocomposite. The significant influential factors such as pH, temperature, sorbent amount, ionic strength, and impurity were discussed. At an initial pH of 7.0 ± 0.1, the highest sorption capacities of CFX and CPX on MIL-53(Al)@AC were 784.14 and 747.91 mg g^-1 (T = 298 K, and sorbent amount = 0.1 g L^-1), which were 1.43 and 1.47 times greater compared to that of MIL-53(Al), respectively. The evaluation of experimental results was implemented through the Langmuir and Freundlich isotherm equations. The isothermal data were described nobly by the Freundlich isotherm, which confirmed multilayer adsorption on heterogeneous surfaces (R² > 0.970). A kinetic study indicated that the nanocomposite could adsorb the majority of cephalosporin antibiotics within 30 min. In addition, the experimental data were evaluated via pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The results indicated that the pseudo-second-order equation agreed more closely with the kinetic data (R² > 0.990). Furthermore, the processes of adsorption were exothermic and spontaneous. The electrostatic attraction, hydrophobic interaction, π-π electron donor-acceptor effect, H-bond, and π-π stacking constituted the main sorption mechanisms. Finally, MIL-53(Al)@AC presented an excellent regeneration performance. Thus, the results revealed the potential application of the MIL-53(Al)@AC nanocomposite for water remediation.

Sustainable adsorptive removal of antibiotics from aqueous streams using Fe3O4-functionalized MIL101(Fe) chitosan composite beads

In this study, we synthesized recyclable Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads for the removal of tetracycline (TC), doxycycline (DC) and ciprofloxacin (CFX) antibiotics from aqueous streams. More than 99% removal efficiency for each antibiotic was achieved at optimum pH, dosage, concentration and contact time. Langmuir adsorption isotherms and pseudo-second-ord er kinetic model were suitable with correlation coefficient values close to 1 for all the antibiotics. Adsorption capacities of 45.33, 33.20 and 31.30 mg g^-1 for TC, DC and CFX, respectively, were reported by the synthesized Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads. The Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads were also tested for their regeneration ability, and a remarkable regeneration ability over up to 5 cycles was observed. The adsorption of TC, DC and CFX on the surface of Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads was governed by the π-π interaction, H-bonding and electrostatic interaction between the antibiotics and adsorbent due to protonation, deprotonation and cation exchange in the aqueous solution. These results showed a good prospect for applying the reported beads towards removing antibiotics from pharmaceutical industry wastewater.

Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective

This review gives a proper dedicated understanding of the contamination level, sources, and biological dangers related with different classes of antibiotics in consumable water. The literature on the adsorption of antibiotics is relatively uncommon and developments are still under progression, especially for adsorbents other than activated carbon. Also, adsorption technique has already been applied vastly for water treatment. Notwithstanding significant progressions, designed natural wastewater treatment frameworks are just bearably effective (48-77%) in the expulsion of antibiotics. Hence, the compilation of available literature especially for antibiotic adsorption was much needed. Moreover, the conventional adsorbents have some limitations of their own. In this study, the main focus was laid on unconventional adsorbents such as Biochar, Biopolymers, Carbon Nanotubes, Clays, Metal-Organic Frameworks, Microalgae and some miscellaneous adsorbents. The mechanism of adsorption by the unconventional adsorbents includes electrostatic interactions, π-π bonding, weak Van der Waal forces, H-bonding and surface complexation, which was similar to that of conventional adsorbents and hence these unconventional adsorbents can easily replace the costlier conventional adsorbents with even better adsorption efficiency. This paper also briefly discussed the thermodynamics, adsorption equilibrium; isotherm and kinetics of adsorption. This review paper seizes the critical advances of adsorption phenomenon at various interfaces and lays the foundation for current scenario associated with further progress. Besides, this study would help in understanding the antibiotic adsorption, cost estimation and future goals that will attract the young the researchers of this field.

Adsorption and catalytic degradation of preservative parabens by graphene-family nanomaterials

Parabens pose increasing threats to human health due to endocrine disruption activity. Adsorption and degradation of parabens by three types of graphene-family nanomaterials (GFNs) were therefore investigated. For a given paraben, the maximum adsorption capacities (Q⁰) followed the order of reduced graphene oxide (RGO) > multilayered graphene (MG) > graphene oxide (GO); for a given GFN, Q⁰ followed the order of butylparaben (BuP) > propylparaben (PrP) > ethylparaben (EtP) > methylparaben (MeP), dominated by hydrophobic interaction. MeP removal by all the three GFNs was highly enhanced (0.55-4.37 times) with the assistance of H₂O₂ due to additional catalytic degradation process, and MG showed the highest removal enhancement. ∙OH was confirmed as the dominant radicals responsible for parabens degradation. For MG and RGO, the metal impurities (Fe, Cu, Mn, and Co) initiated Fenton-like reaction with H₂O₂ to generate ∙OH. GO contained oxygen-centered free radicals, which were responsible for ∙OH formation via transferring electron to H₂O₂. Four degradation byproducts of MeP were identified, including oxalic, propanedioic, fumaric, and 2,5-dihydroxybenzoic acids. Combined with density function theory calculations, the degradation sites and pathways were identified and confirmed. These findings provide useful information on mechanistic understanding towards the adsorption and degradation of parabens by GFNs.

Industrial lignins: the potential for efficient removal of Cr(VI) from wastewater

Cr(VI), a serious threat to human health, widely exists in the effluents of various industrial processes. In this paper, the potential of industrial lignin for efficient removal of Cr(VI) from wastewater was systematically investigated, including pulping black liquor lignin (BLN), enzymolysis lignin (ELN), and SPORL pretreatment spent liquor (FS). The structure characterizations of three lignins were investigated by thermogravimetry (TG), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurement, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). Among these three lignins, BLN showed the highest adsorption amount of Cr(VI) and good selectivity in wastewater simulation. According to the Langmuir model, the calculated maximum adsorption amount of Cr(VI) on ELN, BLN, and FS was 801.57, 864.30, and 642.26 mg g^-1, respectively. The adsorption of Cr(VI) by industrial lignins was a chemisorption process, during which Cr(VI) was reduced to low-toxic Cr(III). This paper provided a promising application for the effective utilization of industrial lignins.

The pH dependent surface charging and points of zero charge. IX. Update

of the points of zero charge (PZC) and isoelectric points (IEP) of various materials published in the recent literature and of older results overlooked in the previous compilations. The roles of experimental conditions, especially of the temperature, of the nature and concentration of supporting electrolyte, and of the type of apparatus are emphasized. The newest results are compared with the zero points reported in previous reviews. Most recent studies were carried out with materials whose pH dependent surface charging is already well-documented, and the newest results are consistent with the older literature. Isoelectric points of Gd(OH)₃, Sm(OH)₃, and TeO₂ have been reported for the first time in the recent literature.

Adsorptive Removal of Anionic Azo Dye New Coccine Using Silica and Silica-gel with Surface Modification by Polycation

In the present work, adsorption of anionic azo dye, new coccine (NCC) on silica and silica-gel in an aquatic environment was discovered. Effective conditions such as adsorption time, pH, the influence of dosage on NCC adsorption using strong polycation, poly-diallyl-dimethylammonium chloride (PDADMAC) modified silica (PMS) and PDADMAC modified silica-gel (PMSG) were systematically studied. The removal of NCC using PMS and PMSG were much higher than that using raw silica and silica-gel without PDADMAC in all pH ranges from 3 to 10. The adsorption of NCC onto PMS and PMSG was achieved maxima at the same conditions of contact time 30 min, pH 6. The optimum adsorbent dosages of PMS and PMSG for NCC removal were 10 and 20 mg·mL-1, respectively. Experimental results of NCC adsorption isotherms onto PMS and PMSG at different ionic strength were fitted by Langmuir and Freundlich models. The NCC removal efficiencies using PMS and PMSG were higher than 87%, indicating that PMS and PMSG are novel and reusable adsorbents for removal of anionic dye. Based on adsorption isotherms, and surface group changes after PDADMAC modification and NCC adsorption examined by Fourier transform infrared spectroscopy (FTIR), we demonstrate that electrostatic interaction between positively charged adsorbents' surfaces and negative sulfonic groups of NCC are the main driving force for anionic azo dye adsorption onto PMS and PMGS adsorbents.

Removal of Cd(II) from Micro-Polluted Water by Magnetic Core-Shell Fe3O4@Prussian Blue

A novel core-shell magnetic Prussian blue-coated Fe3O4 composites (Fe3O4@PB) were designed and synthesized by in-situ replication and controlled etching of iron oxide (Fe3O4) to eliminate Cd (II) from micro-polluted water. The core-shell structure was confirmed by TEM, and the composites were characterized by XRD and FTIR. The pore diameter distribution from BET measurement revealed the micropore-dominated structure of Fe3O4@PB. The effects of adsorbents dosage, pH, and co-existing ions were investigated. Batch results revealed that the Cd (II) adsorption was very fast initially and reached equilibrium after 4 h. A pH of 6 was favorable for Cd (II) adsorption on Fe3O4@PB. The adsorption rate reached 98.78% at an initial Cd (II) concentration of 100 μg/L. The adsorption kinetics indicated that the pseudo-first-order and Elovich models could best describe the Cd (II) adsorption onto Fe3O4@PB, indicating that the sorption of Cd (II) ions on the binding sites of Fe3O4@PB was the main rate-limiting step of adsorption. The adsorption isotherm well fitted the Freundlich model with a maximum capacity of 9.25 mg·g-1 of Cd (II). The adsorption of Cd (II) on the Fe3O4@PB was affected by co-existing ions, including Cu (II), Ni (II), and Zn (II), due to the competitive effect of the co-adsorption of Cd (II) with other co-existing ions.