Encapsulation of iron nanoparticles with magnesium hydroxide shell for remarkable removal of ciprofloxacin from contaminated water

Differential and mechanism analysis of sulfate influence on the degradation of 1,1,2- trichloroethane by nano- and micron-size zero-valent iron

The in-situ reduction of zero-valent iron (ZVI) is an effective method for removing chlorinated aliphatic hydrocarbons (CAHs) from groundwater. The heterogeneity of environmental conditions is also crucial in affecting dechlorination efficiency. Until now, the effect of Sulfate (SO42-) on ZVI activity has been debated, and the related mechanism research on SO42- behaviour during the abiotic reduction process of chlorinated alkanes is still lacking. In this study, the impacts of SO42- concentrations (0, 2, 4, 8, 80 mM) on the degradation of 1,1,2-trichloroethane (1,1,2-TCA) by micron-size ZVI (mZVI) and nano-size ZVI (nZVI) were systematically investigated. For mZVI, Kobs increased by 0.6 (2 mM), 0.5 (4 mM), 1.1 (8 mM), and 1.6 times (80 mM). For nZVI, Kobs decreased by 32% (2 mM), 39% (4 mM), 45% (8 mM), and 9% (80 mM). The results showed that SO42- increased the rate of 1,1,2-TCA degradation by mZVI but weakened the reduction performance of nZVI; however, this inhibition was reduced when the concentration reached 80 mM. SO42- controlled the degradation of 1,1,2-TCA mainly through the formation of different iron-sulfate complexes on the ZVI surface: water-soluble bidentate iron-sulfate complexes formed on the mZVI surface promoted the corrosion of the oxide layer and accelerated the reduction of 1,1,2-TCA, monodentate complexes mainly formed on the nZVI surface inhibited the reduction of 1,1,2-TCA by blocking surface sites. These results demonstrate the proof of concept to assist land managers in the field application of ZVI technology for the remediation of CAHs contaminated sites with different background concentrations of SO42-.

Towards sorptive eradication of pharmaceutical micro-pollutant ciprofloxacin from aquatic environment: A comprehensive review

Antibiotics are widely prioritized pharmaceuticals frequently adopted in medication for addressing numerous ailments of humans and animals. However, the non-judicious disposal of ciprofloxacin (CIP) with concentration levels exceeding threshold limit in an aqueous environment has been the matter of growing concern nowadays. CIP is found in various waterways with appreciable mobility due to its limited decay in solidified form. Hence, the effective eradication strategy of this non-steroidal anti-inflammatory antibiotic from aqueous media is pivotal for preventing the users and the biosphere from their hazardous impacts. Reportedly several customary techniques like reverse osmosis, precipitation, cross-filtration, nano-filtration, ion exchange, microbial remediation, and adsorption have been employed to eliminate CIP from water. Out of them, adsorption is ascertained to be a potential method because of lesser preliminary investment costs, ease of operation, greater efficiency, less energy usage, reduced chemical and biological slurry production, and ready availability of precursor materials. Towards remediation of ciprofloxacin-laden water, plenty of researchers have used different adsorbents. However, the present-day challenge is opting the promising sorbent and its application towards industrial scale-up which is vital to get reviewed. In this article, adsorbents of diverse origins are reviewed in terms of their performances in CIP removal. The review stresses the impact of various factors on sorptive assimilation of CIP, adsorption kinetics, isotherms, mechanism of ionic interaction, contrivances for CIP detection, cost estimation and reusability assessments of adsorbents also that may endorse the next-generation investigators to decide the efficacious, environmental appealing and cost-competitive adsorbents for effective riddance of CIP from wastewater.

In-situ methane enrichment in anaerobic digestion of food waste slurry by nano zero-valent iron: Long-term performance and microbial community succession

In this work, nano zero-valent iron (nZVI) was added to a lab-scale continuous stirring tank reactor (CSTR) for food waste slurry treatment, and the effect of dosing rate and dosage of nZVI were attempted to be changed. The results showed that anaerobic digestion (AD) efficiency and biomethanation stability were optimum under the daily dosing and dosage of 0.48 g/gTCOD. The average daily methane (CH4) yield reached 495.38 mL/gTCOD, which was 43.65% higher than that at control stage, and the maximum CH4 content reached 95%. However, under single dosing rate conditions, high nZVI concentrations caused microbial cell rupture and loosely bound extracellular polymeric substances (LB-EPS) precipitation degradation. The daily dosing rate promoted the hydrogenotrophic methanogenesis pathway, and the activity of coenzyme F420 increased by 400.29%. The microbial analysis indicated that daily addition of nZVI could promote the growth of acid-producing bacteria (Firmicutes and Bacteroidetes) and methanogens (Methanothrix).

Dewatered Sludge Decorated with Nanoparticles for Alum Sludge Conditioning towards the Concept of "End-of-Waste"

The circular economy concept is leading environmental engineering in the search for "End-of-Waste" criteria. Untreated waste residue results from drinking water treatment plants, causing severe environmental issues, and its reuse is essential. In this regard, this investigation introduces the beneficial reuses of alum sludge cake to close the loop between sludge waste generation and reuse. Considering alum sludge as a resource for dewatering instead of its categorization as a waste reflects an "End-of-Waste" approach. Alum sludge cake was thermally calcined at 400 °C and named thermally treated alum sludge cake (TAS-cake). In this study, TAS-cake decorated with magnetite with a percent weight of 5 to 1%, respectively, was labeled as TAS-cake@Fe-(5-1). X-ray diffraction (XRD) and morphologies were applied to characterize the hybrid composite. A Fenton-based hybrid composite was applied to extrude water from alum sludge for 7 min of conditioning time. Furthermore, the factorial design based on response surface methodology (RSM) was applied to optimize the operational variables. TAS-cake@Fe-(5-1) and hydrogen peroxide revealed 1.2 g/L and 740 mg/L doses at pH 3.0, showing pronounced performance and revealing the highest capillary suction time (CST) reduction, which reached 53%. A temperature increase also showed a pronounced enhancement effect on the sludge dewaterability that reached 72% when 55 °C was applied. Thus, such a novel conditioner is a promising candidate for alum sludge conditioning.

Epsilon-MnO2 simply prepared by redox precipitation as an efficient catalyst for ciprofloxacin degradation by activating peroxymonosulfate

Four kinds of manganese oxides were successfully prepared by hydrothermal and redox precipitation methods, and the obtained oxides were used for CIP removal from water by activating PMS. The microstructure and surface properties of four oxides were systematically characterized. The results showed that ε-MnO2 prepared by the redox precipitation method had large surface area, low crystallinity, high surface Mn(III)/Mn(Ⅳ) ratio and the highest activation efficiency for PMS, that is, when the concentration of PMS was 0.6 g/L, 0.2 g/L ε-MnO2 could degrade 93% of CIP within 30 min. Multiple active oxygen species, such as sulfate radical, hydroxyl radical and singlet oxygen, were found in CIP degradation, among which sulfate radical was the most important one. The degradation reaction mainly occurred on the surface of the catalyst, and the surface hydroxyl group played an important role in the degradation. The catalyst could be regenerated in situ through the redox reaction between Mn4+ and Mn3+. The ε-MnO2 had the advantages of simple preparation, good stability and excellent performance, which provided the potential for developing new green antibiotic removal technology.

High-efficient adsorption for versatile adsorbates by elastic reduced graphene oxide/Fe3O4 magnetic aerogels mediated by carbon nanotubes

Fabrication of highly elastic three-dimensional aerogel adsorbents with outstanding adsorption capacities is a long pursuit for the treatment of industrial contaminated water. In this work, a magnetic reduced graphene oxide (rGO)/Fe₃O₄/carbon nanotubes (CNTs) aerogel material was constructed by the electrostatic attraction between the negatively charged GO and positively charged CNTs following a one-pot water bath treatment. The as-synthesized aerogel demonstrated high compressive stress (28.4 kPa) and lower density (24.11 mg/cm³) with exceptional adsorption capacities for versatile adsorbates which are attributed to CNTs and magnetic Fe₃O₄ nanoparticles. The effect of pH, initial concentration of adsorbates (dyes, Cd (ІІ) ions, organic solvents, and pump oil), content of CNTs and cyclic times on the adsorption capacities of the aerogel were investigated in detail. Furthermore, from simulation, the adsorption kinetics, and thermodynamics of the aerogel for adsorbates were more satisfied by endothermic quasi-second-order kinetic model with characteristic physical adsorption. Thus, the optimized rGO/Fe₃O₄/CNTs-10 aerogel adsorbent can be used as a powerful and versatile tool to deal with contaminated industrial or domestic wastewater.

Comparative Evaluation of Bioefficiency and Photocatalytic Activity of Green Synthesized Bismuth Oxide Nanoparticles Using Three Different Leaf Extracts

Nanotechnology has emerged as a promising method for wastewater recycling. In this line, the current study emphasizes the leaf-extract-mediated biosynthesis of bismuth oxide nanostructures (BiONPs) using three different plants, namely Coldenia procumbens Linn (Creeping Coldenia), Citrus limon (Lemon), and Murraya koenigii (Curry) through a greener approach and evaluates their biological properties as well as photocatalytic performance for the first time. As-synthesized BiONPs were physiochemically characterized using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray analysis (EDAX). Using the well diffusion method, research on the antibacterial efficiency of BiONPs against human pathogenic Gram-positive bacteria, such as Staphylococcus aureus and Enterococcus faecalis, and Gram-negative bacteria, including Escherichia coli and Klebsiella pneumonia, revealed that Gram-negative bacteria exhibited relatively strong activity. The larvicidal activity assessed against Aedes aegypti and Aedes albopictus mosquito larvae reveals promising larvicidal activity with a minimal dosage of BiONPs with LC₅₀ values of 5.53 and 19.24 ppm, respectively, after 24 h of exposure. The excellent photocatalytic activity of as-synthesized BiONPs was demonstrated through the photodegradation of malachite green (MG) and methylene blue (MB) dyes with respective degradation performance parameters of 70 and 90%. The biogenic synthetic approach reported here enables the scalable commercial synthesis of bismuth nanostructures for their widespread use in catalysis for wastewater treatment and environmental cleanup.

Removal of Ciprofloxacin from Water by a Potassium Carbonate-Activated Sycamore Floc-Based Carbonaceous Adsorbent: Adsorption Behavior and Mechanism

In this study, a porous carbonaceous adsorbent was prepared from sycamore flocs by pyrolysis method and K₂CO₃ activation. The effects of preparative conditions of the material on its adsorptive property were explored. The optimal material (SFB_2-900) was obtained with a K₂CO₃/biochar mass ratio of 2:1 at an activation temperature of 900 °C, possessing a huge surface specific area (1651.27 m²/g). The largest adsorption capacity for ciprofloxacin on SFB_2-900 was up to 430.25 mg/g. The adsorption behavior was well described by the pseudo-second-order kinetic model and the Langmuir isothermal model. Meanwhile, this process was spontaneous and exothermic. The obtained material showed excellent adsorption performance in the conditions of diverse pH range, ionic strength, and water quality of the solution. The optimum adsorption conditions (pH = 7.01, dosage = 0.6 g/L, and C₀ = 52.94 mg/L) determined based on the response surface methodology were in accordance with the practical validation consequences. The good regeneration effect of SFB_2-900 manifested that this material had great practical application potential. Combining the experimental results and density functional theory calculation results, the adsorption mechanisms mainly included pore filling, π-π EDA interactions, electrostatic interactions, and H-bonds. The material could be regarded as a novel and high-efficiency adsorbent for antibiotics. Additionally, these findings also provide reference for the reuse of waste biomass in water treatment.

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.

Mechanistic insight into the degradation of ciprofloxacin in water by hydroxyl radicals

Ciprofloxacin (CIP), an effective antibacterial drug, is widely used to treat bacterial infections in humans and animals. However, drug pollution from residues and the development of resistant genes may pose serious ecological risks. Among the known methods of CIP degradation, advanced oxidation technology initiated by hydroxyl radicals exhibits great potential. However, an in-depth study of the degradation mechanism is difficult because of the limitations of the testing methods. In this study, CIP oxidation by hydroxyl radicals was evaluated using density functional theory (DFT), and the thermodynamics, kinetics, and toxicity were investigated. The results show that CIP oxidation occurs mainly through the piperazine ring, benzene ring, and CC. High reactivity is achieved in the initial reactions, where only five reactions are not thermodynamically spontaneous. Reactions involving direct hydrogen abstraction by oxygen in this system are superior to the indirect reactions. Some theoretically predicted products, such as P6 and P11, are consistent with those reported in previous experiments, indicating that the theoretical study can provide supplementary information about the oxidation paths. The branching ratios for the hydrogen atom abstraction and addition reactions were 37. 45% and 62.55%, respectively. Finally, this reaction system is completely nontoxic based on toxicity assessment.

Waste-Based Ceramsite for the Efficient Removal of Ciprofloxacin in Aqueous Solutions

Ciprofloxacin (CIP), a compound with bioaccumulation toxicity and antibiotic resistance, is frequently detected in water at alarming concentrations, which is becoming an increasing concern. In this study, a low-cost ceramsite was developed from industrial solid wastes through sintering to remove CIP from wastewater. The effects of adsorbent dosage, initial pH, contact time, initial CIP concentration, and temperature were explored. More than 99% of CIP (20-60 mg/L) was removed at around pH 2-4 by the ceramsite. The kinetic data fitted well with the pseudo-second-order model, revealing that chemisorption was the main rate-determining step. The isotherm data was better described by the Freundlich model, suggesting that CIP was removed by the formation of multiple layers on the heterogeneous surface. Moreover, the removal efficiency was practically higher than 95% during five regeneration cycles, when different regeneration methods were used, including calcination, HCl, and NaOH washing, indicating that the ceramsite exhibited outstanding reusability in removing CIP. The primary mechanism of CIP removal by the ceramsite was found to be the synergism of adsorption and flocculation, both of which depended on the release of Ca²⁺ from the ceramsite. In addition, strong Ca-CIP complexes could be formed through surface complexation and metal cation bridging between Ca²⁺ and different functional groups in CIP.

Reaction of decabromodiphenyl ether with organo-modified clay-templated zero-valent iron in water-tetrahydrofuran solution: Nano- to micrometric scale effects

Smectite clay-templated nanoscale zero-valent iron (CZVI) was modified with tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA) to achieve organoclay-templated ZVI (OCZVI). The reactivity of various OCZVIs was evaluated on the basis of degradation of decabromodiphenyl ether (DBDE) in tetrahydrofuran (THF)-water binary solution. Characterization of OCZVI interlayer at nanometric scale indicated that the clay particles had the domains with three basal spacings in the THF/water solution. In the 50 % THF solution TMPA modification promoted the formation of the domains with a basal spacing at 1.56 nm, which could promote the degradation of DBDE. At the micrometric scale, in the 90 % THF solution TMA and TMPA modification tended to enhance the aggregation of OCZVI particles, while the HDTMA modification reduced the aggregation, and high percentage of modification yielded viscous gel structures. The relatively rapid sedimentation processes in 90 % THF solution (compared to that in 50 % THF solution) and formation gel structures could reduce the access of DBDE to the interlayer reactive nZVIs, and lead to the significant reduction in reaction rate. These results provide important insights to the organo-modification on clays which could alter their orientations and dispersion in organic-water binary solution to achieve the desired reactivity on confined clay surfaces.

Two-Dimensional Modeling of Nano Zero-Valent Iron Transport and Retention before and after Phosphate Adsorption

The mobility of nano zero-valent iron (nZVI) will greatly affect its practical application as a remediation material for contaminated groundwater. One-dimensional (1D) column tests are commonly used in previous work to study its migration behavior, but the two-dimensional (2D) test is still very limited. This study reports a novel research system to study the 2D transport and retention behavior of colloids and solutes, which includes a 2D model test setup and the corresponding image analysis method. The transport behaviors of methyl orange (MO), nZVI, and phosphate-loaded nZVI (PnZVI) are studied using this system. The results show that the research system can reasonably describe the tempo-spatial concentration distribution of colloids and solutes. After phosphate adsorption, the mobility of nZVI is enhanced due to the increase in negative surface charge, which implies a potential environmental risk of nZVI to facilitate contaminant transport. The migration of PnZVI is not significantly influenced by its density, which is faster than MO in the longitudinal direction. The range of the plume of PnZVI in the longitudinal direction is larger than that of MO, which implies that PnZVI has a stronger longitudinal dispersion than MO.

Impacts of shell structure on nitrate-reduction activity and air stability of nanoscale zero-valent iron

Nanoscale zero-valent iron (nZVI) has been intensively studied for pollution control because of its high reductive activity and environmental benignity, but the poor reaction selectivity and the aging problem have limited its practical decontamination application. Here, we shed light on the impacts of nZVI shell structure on its reactivity and air stability by systematically comparing two nZVI materials with distinct iron oxide shells. The nZVI with highly crystalline and weakly hydrophilic shell exhibited ninefold higher intrinsic activity for nitrate reduction and significantly improved air stability than that with amorphous, hydrophilic iron hydroxide oxide shell. The compact-structured crystalline shell of nZVI facilitated more efficient interfacial electronic transfer for nitrate reduction and suppressed side reaction of hydrogen evolution. The protective hematite shell endowed the nZVI with significantly improved anti-aging ability, and the reducing force remained 92.6% after exposed to air for 10 days due to decreased oxygen diffusion. This work provides a better understanding of the pollutant degradation behavior of nZVI and may guide an improved synthesis and environmental application of nZVI.

Zero-valent bimetallic catalyst/absorbent for simultaneous facilitation of MgSO3 oxidation and arsenic uptake

Cobalt (Co)-based catalysts can efficiently reduce the heat waste from sulfate concentration by enhancing sulfite oxidation during wet flue gas desulfurization system. However, arsenic (As) can poison such catalysts and migrate into the sulfate by-products, resulting in severe secondary pollution. In this study, a zero-valent Co/iron (Fe)-based nanoparticle (NZV-Co₂Fe₁) was fabricated and applied as a bifunctional catalyst/adsorbent. The catalytic stability of the Co-based catalyst was enhanced by the introduction of Fe because the poisonous effect of As was substantially suppressed because of the high adsorption capacity of Fe for As. Compared with the noncatalytic benchmark, the presence of 0.5 g/L NZV-Co₂Fe₁ can increase the rate of MgSO₃ oxidation by approximately 12-fold even at a high concentration of As (2.5 mg/L). The Langmuir model was fitted to the As adsorption isotherms, indicating that As uptake is a single-layer adsorption process. The pseudo-second-order kinetic model indicated that As was removed through chemisorption. The oxidation pathway of As(III) involves reactive radicals (mainly OH, SO₄^- and SO₅^-) and ligand-to-metal charge transfer between SO₃^2- and Co²⁺. The availability of MgSO₃ improved the removal efficiency at high concentrations of As(III) (1 mg/L). These results indicate that using NZV-Co₂Fe₁ as a catalyst to purify the by-products of flue gas desulfurization can effectively prevent secondary pollution.

Enhanced removal performance of zero-valent iron towards heavy metal ions by assembling Fe-tannin coating

Heavy metals (HMs) pose serious threats to both human and environmental health and therefore, effective and low-cost techniques to remove HMs are urgently required. Here we report a facile Fe-tannin coating method for zero-valent iron (ZVI) including nanoparticles (nZVI) and foam (Fe_foam), and demonstrate that the generated Fe-tannin coating would remove the inherent passive iron oxide shell of ZVI and provide channels for the galvanic replacement reaction between ZVI and HM ions. Electrochemical characterizations demonstrate that the Fe core of the modified ZVI materials could be easily oxidized and transfer electrons to HM ions owing to the facile mass transport and charge transfer. In 40 min, nZVI@Fe-TA exhibits excellent performances for Cd(II), Ni(II), Pb(II), Hg(II), Cu(II) and Cr(VI) removal, with the apparent removal rate constants of 0.083, 0.085, 0.083, 0.073, 0.092 and 0.078 min^-1, respectively. It is found that the surface area normalized rate constants of nZVI@Fe-TA are 4-7 times higher than that of nZVI@Fe₂O₃ counterpart, suggesting that the improved HM removal reactivity of nZVI@Fe-TA is derived from the surface modification. Moreover, nZVI@Fe-TA has advantages in resisting interference and in the simultaneous removal of different HM ions. Under a 30 min hydraulic retention time, Fe_foam@Fe-TA could remove 98% HMs in the successive process. For real electroplating wastewater, Fe_foam@Fe-TA exhibits excellent performance for Cr(VI) and Ni(II) removal, producing effluent of stable quality that meets local emission regulation. This study provides a facile strategy to remove the inherent passive iron oxide shell and enhance the HM removal reactivity for ZVI materials.

Effective Removal of Refractory Pollutants through Cinnamic Acid-Modified Wheat Husk Biochar: Experimental and DFT-Based Analysis

The removal of refractory pollutants, i.e., methylene blue (MB) and ciprofloxacin (CIP), relies heavily on sorption technologies to address global demands for ongoing access to clean water. Because of the poor adsorbent–pollutant contact, traditional sorption procedures are inefficient. To accomplish this, a wheat husk biochar (WHB), loaded with cinnamic acid, was created using a simple intercalation approach to collect dangerous organic pollutants from an aqueous solution. Batch experiments, detecting technologies, and density functional theory (DFT) calculations were used to investigate the interactions at the wheat husk biochar modified with cinnamic acid (WHB/CA) and water interface to learn more about the removal mechanisms. With MB (96.52%) and CIP (94.03%), the functionalized WHB exhibited outstanding adsorption capabilities, with model fitting results revealing that the adsorption process was chemisorption and monolayer contact. Furthermore, DFT studies were performed to evaluate the interfacial interaction between MB and CIP with the WHB/CA surface. The orbital interaction diagram provided a visual representation of the interaction mechanism. These findings open up a new avenue for researchers to better understand adsorption behavior for the utilization of WHB on an industrial scale.

Synthesis, performance, and mechanisms of strontium ferrite-incorporated zeolite imidazole framework (ZIF-8) for the simultaneous removal of Pb(II) and tetracycline

In this study, strontium ferrite (SF)-incorporated zeolite imidazole framework (ZIF-8) (SFZIF-8) that can simultaneously uptake Pb(II) and tetracycline (TC) in solution was synthesized and characterized. The physicochemical properties of the as-prepared SFZIF-8 were characterized by various functional groups, higher average pore diameter (3.414 nm), and stronger negative charge (-30.5 mV). Adsorption kinetics, isotherms, effect of various water conditions including solution pH and temperature, and reusability were studied to evaluate its adsorption performance. The adsorption capacity of SFZIF-8 was compared with that of commonly used adsorbents (powder and granular activated carbon). SFZIF-8 showed much higher adsorption performance (429.6 mg/g and 433.4 mg/g for Pb(II) and TC, respectively) than powder activated carbon (129.9 mg/g and 142.0 mg/g for Pb(II) and TC, respectively) and granular activated carbon (249.3 mg/g and 263.0 mg/g for Pb(II) and TC, respectively) in Pb(II) and TC binary solutions. The SFZIF-8 adsorption behaviors for the removal of Pb(II) and TC were explained by the pseudo-first-order and Langmuir models from the adsorption kinetics and isotherm experiments, respectively. The regenerated SFZIF-8 exhibited a competitive performance even after the third cycle. These results indicate that Pb(II) and TC can be removed with SFZIF-8 via electrostatic attraction, surface complexation, hydrogen bonding, and π-π interactions. Therefore, by exhibiting effective and efficient adsorption performance, SFZIF-8 nanocomposites can be utilized as alternative and promising adsorbents for the simultaneous removal of both Pb(II) and TC.

Aqueous monomethylmercury degradation using nanoscale zero-valent iron through oxidative demethylation and reductive isolation

This paper proposes a Fenton-like reaction activated by nanoscale zero-valent iron (nZVI) for aqueous monomethylmercury (MMHg) decomposition. Reacting 10 μg L^-1 MMHg with 280 mg L^-1 nZVI removed 70% of the aqueous MMHg within 1 min, and its main product was aqueous Hg(II). Within 1 - 5 min, the aqueous Hg(II) decreased while the aqueous, solid, and gas-phase Hg(0) increased with 92% MMHg removal. Then, a secondary Hg(II) reduction to solid Hg(0) was prevalent within 30 - 60 min, with 98% MMHg removal. Diverse-shaped magnetite crystals were observed on the surface of nZVI in 2 h, suggesting that Fe(II) oxidation on magnetite can be a source of electrons for secondary Hg(II) reduction. When FeCl₂ and H₂O₂ were added to the MMHg solution without nZVI, 99% of the MMHg changed to Hg(II) within 1 min. The reactive oxygen species (ROS) produced by the Fenton-like reaction accounted for the rapid demethylation but not for the further reduction of Hg(II) to Hg(0). The results suggest a three-step pathway of MMHg decomposition by nZVI: (1) rapid MMHg demethylation by ROS; (2) rapid Hg(II) reduction by Fe(0); and (3) slow Hg(II) reduction by magnetite on the nZVI surface.

Biomineralization and biotechnological applications of bacterial magnetosomes

Magnetosomes intracellularly biomineralized by Magnetotactic bacteria (MTB) are membrane-enveloped nanoparticles of the magnetic minerals magnetite (Fe₃O₄) or greigite (Fe₃S₄). MTB thrive in oxic-anoxic interface and exhibit magnetotaxis due to the presence of magnetosomes. Because of the unique characteristic and bionavigation inspiration of magnetosomes, MTB has been a subject of study focused on by biologists, medical pharmacologists, geologists, and physicists since the discovery. We herein first briefly review the features of MTB and magnetosomes. The recent insights into the process and mechanism for magnetosome biomineralization including iron uptake, magnetosome membrane invagination, iron mineralization and magnetosome chain assembly are summarized in detail. Additionally, the current research progress in biotechnological applications of magnetosomes is also elucidated, such as drug delivery, MRI image contrast, magnetic hyperthermia, wastewater treatment, and cell separation. This review would expand our understanding of biomineralization and biotechnological applications of bacterial magnetosomes.

Enhanced Ciprofloxacin Removal from Aqueous Solution Using a Chemically Modified Biochar Derived from Bamboo Sawdust: Adsorption Process Optimization with Response Surface Methodology

Contamination of water by ciprofloxacin has become a significant concern due to its adverse health effects and growing evidence of antimicrobial-resistant gene evolution. To this end, a chemically modified bamboo biochar was prepared from bamboo sawdust to effectively remove ciprofloxacin (CIP) from an aqueous solution. Under similar adsorption conditions, the modified bamboo biochar (MBC) has an excellent CIP removal efficiency (96%) compared to unmodified bamboo biochar (UBC) efficiency (45%). Thus, MBC was used in batch adsorption experiments, and the process was optimized with the central composite design (CCD) framework of response surface methodology (RSM). Sorption process parameters such as initial CIP concentration, pH, adsorbent dose, and contact time were studied and found to have a significant effect on CIP removal. The optimal CIP removal (96%) was obtained at MBC dose (0.5 g L-1), CIP initial concentration (20 mg L-1), pH (7.5), and contact time (46 min). The adsorption kinetic data were well described by the pseudo-second-order model ( $R^2=0.999$ ), and both Langmuir ( $R^2=0.994$ ) and Freundlich ( $R^2=0.972$ ) models gave the best fit in CIP adsorption isotherm analysis. The maximum monolayer adsorption capacity of the MBC was 78.43 mg g-1 based on the Langmuir isotherm model. These results suggest that CIP adsorption was mainly controlled by chemisorption. Moreover, the CIP adsorption process was endothermic and spontaneous. Overall, MBC is a low-cost, efficient, and recyclable adsorbent for eliminating emerging contaminants such as ciprofloxacin from an aqueous solution.

Selective Oxidation of Cellulose—A Multitask Platform with Significant Environmental Impact

Raw cellulose, or even agro-industrial waste, have been extensively used for environmental applications, namely industrial water decontamination, due to their effectiveness, availability, and low production cost. This was a response to the increasing societal demand for fresh water, which made the purification of wastewater one of the major research issue for both academic and industrial R&D communities. Cellulose has undergone various derivatization reactions in order to change the cellulose surface charge density, a prerequisite condition to delaminate fibers down to nanometric fibrils through a low-energy process, and to obtain products with various structures and properties able to undergo further processing. Selective oxidation of cellulose, one of the most important methods of chemical modification, turned out to be a multitask platform to obtain new high-performance, versatile, cellulose-based materials, with many other applications aside from the environmental ones: in biomedical engineering and healthcare, energy storage, barrier and sensing applications, food packaging, etc. Various methods of selective oxidation have been studied, but among these, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) (TEMPO)-mediated and periodate oxidation reactions have attracted more interest due to their enhanced regioselectivity, high yield and degree of substitution, mild conditions, and the possibility to further process the selectively oxidized cellulose into new materials with more complex formulations. This study systematically presents the main methods commonly used for the selective oxidation of cellulose and provides a survey of the most recent reports on the environmental applications of oxidized cellulose, such as the removal of heavy metals, dyes, and other organic pollutants from the wastewater.

Multi-component removal of Pb(II), Cd(II), and As(V) over core-shell structured nanoscale zero-valent iron@mesoporous hydrated silica

The application of nanomaterials for the removal of heavy metals has received a great deal of attention because of their high efficiencies in the environment. But it is difficult to remove multiple heavy metals simultaneously with high efficiency and stability. Herein, the core-shell structured nanoscale zero-valent iron (nZVI) encapsulated with mesoporous hydrated silica (nZVI@mSiO₂) were prepared for efficient removal of heavy metals including Pb(II), Cd(II), and metalloid As(V). The material prepared uniformly with a high surface area (147.7 m² g^-1) has a nZVI core with the particle size of 20-60 nm and a modified dendritic mesoporous shell of 19 nm. 0.15 g L^-1 of the optimal material exhibited an extraordinary performance on removing Cd(II) and the maximum adsorption capacity for Pb(II), Cd(II), and As(V) reached 372.2 mg g^-1, 105.2 mg g^-1, and 115.2 mg g^-1 with a pH value at 5.0, respectively. The dissolved iron during the reaction showed that the mesoporous silica (mSiO₂) played an important role in enhancing the stability of nZVI. In addition, the competitive relationship between the coexistence of two heavy metals was discussed and it was found that the removal efficiency of the material for both was improved when Cd(II) and As(V) were removed synergistically.

The multi-process reaction model and underlying mechanisms of 2,4,6-trichlorophenol removal in lab-scale biochar-microorganism augmented ZVI PRBs and field-scale PRBs performance

This work developed calcium alginate (CA) embedded zero-valent iron (ZVI@CA) and CA embedded biochar (BC) immobilized microorganism (BC&Cell@CA) gel beads as alternative to conventional Fe⁰ permeable reactive barriers for treating groundwater contaminated with 2,4,6-trichlorophenol (2,4,6-TCP). Lab-scale and field-scale biochar-microorganism augmented PRBs (Bio-PRBs) were constructed and tested. The underlying mechanisms were revealed by a multi-source data calibrated multi-process reaction model, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-throughput sequencing. Moreover, calibrated advection-dispersion (a) coupled with the two-site sorption (K_d) and chemical-biological multi-process reaction (λ) model were used for revealing 2,4,6-TCP transport behavior and optimizing Bio-PRBs. Compared to that in the ZVI@CA (0.004 h^-1) system, the reaction rate (0.011 h^-1) of 2,4,6-TCP increased by 175% in the combined chemical-biological batch system. Moreover, chemical-biological augmentation significantly improved the retardation effect of Bio-PRBs for 2,4,6-TCP. It came from that chemical-biological augmentation significantly decreased the dispersivity a (0.53 to 0.20 cm), and increased the distribution coefficient K_d (2.20 to 19.00 cm³ mg^-1), the reaction rate λ (2.40 to 3.60 day^-1), and the fraction (30% to 80%) of first-order kinetic sorption of 2,4,6-TCP in the lab-scale one-dimensional Bio-PRBs. Moreover, versatile functional bacteria Desulfitobacterium was crucial in the transformation of Fe (III) iron oxides. The diversity and richness of archaea in the reaction solution were improved by ZVI@CA gel beads addition. Furthermore, the field-scale reaction system was designed to remediate the chlorinated organic compounds and Benzene Toluene Ethylbenzene & Xylene contaminated groundwater in a pesticide factory site. The field test results demonstrated it is a promising technology to construct vertical reaction columns or horizontal Bio-PRBs for the efficient remediation of actually contaminated groundwater.

Enhanced biogas biological upgrading from kitchen wastewater by in-situ hydrogen supply through nano zero-valent iron corrosion

The in-situ hydrogen supply by nano zero-valent iron (nZVI, nFe⁰) corrosion provided a feasible way to improve the efficiency of biogas biological upgrading. This work studied the effects of nZVI at different dosages (0, 2, 4, 6, 8 and 10 g/L) on anaerobic digestion of kitchen wastewater by two buffer systems 2-[4-(2-hydroxyethyl) piperazin-1-yl] ethanesulfonic acid (HEPES) and sodium hydrogen carbonate (NaHCO₃). The addition of nZVI improved the content of methane (CH₄) and stability of anaerobic digestion process. In HEPES buffer system, the CH₄ was all increased and the maximum reached 90.51% with 10 g/L nZVI, higher than 32.25% compared to the control. The maximum hydrogen enrichment (HE) was 113 ppb after nZVI addition, indicating the mass transfer efficiency of hydrogen (H₂) was improved. Microbial community analysis showed that the total relative abundance of Methanobacterium and Methanolinea at 10 g/L nZVI was 53.72%, which was 1.62 times of the control group. However, in the NaHCO₃ buffer system with 10 g/L nZVI addition, the content of CH₄ and the loosely bound extracellular polymeric substances (LB-EPS) was lower than the control. The results indicated that the addition of nZVI was feasible for biogas upgrading, and the bidirectional effect of nZVI on the promotion or inhibition of bio-methanation might be related to the buffer system of the anaerobic process.

Influence of physicochemical parameters on PPCP occurrences in the wetlands

There have been many global studies on the occurrence and distribution of pharmaceuticals and personal care products (PPCPs) in the aquatic resources, but reports on the effects of physicochemical properties of water on their concentrations are very scarce. The amounts and removal of these contaminants in various environmental media are dependent on these physicochemical properties, which include pH, temperature, electrical conductivity, salinity, turbidity, and dissolved oxygen. Here, we reviewed the influence of these properties on determination of PPCPs. Reports showed that increase in turbidity, electrical conductivity, and salinity gives increase in concentrations of PPCPs. Also, neutral pH gives higher PPCP concentrations, while decrease in temperature and dissolved oxygen gives low concentration of PPCPs. Nevertheless, it is quite challenging to ascertain the influence of water quality parameters on the PPCP concentration, as other factors like climate change, type of water, source of pollution, persistence, and dilution factor may have great influence on the concentration of PPCPs. Therefore, routine monitoring is suggested as most water quality parameters vary because of effects of climate change.

Zero-valent iron supported on expanded graphite from spent lithium-ion battery anodes and ferric chloride for the degradation of 4-chlorophenol in water

Zero-valent iron supported with expanded graphite (ZVI/EG) were successfully prepared from ferric chloride and the graphite of spent lithium-ion battery (LIB) using carbothermic reduction as a new approach for recycling spent LIB. ZVI/EG composites synthesized with different ZVI mass ratios were used as catalysts for the 4-chlorophenol (4-CP) removal from water by heterogeneous Fenton reactions. ZVI/EG composites showed a BET specific surface area of 11.295 m² g^-1. ZVI/EG synthesized from expandable graphite and ferric chloride with mass ratio of 2:1 (ZVI/EG-2) showed the highest removal percentage of 4-CP, being 97% in 1 h. The degradation rate fitted to a pseudo first-order model better, and reached 0.0527 min^-1 for ZVI/EG-2. Moreover, ZVI/EG-2 showed high reactivity for 4-CP removal even in the sixth reuse cycle, being 82%. Hydroquinone and 4-chlorocatechol were identified as the intermediate products of 4-CP degradation. Increasing the ZVI/EG-2 dosage can enhance the 4-CP removal percentage through offering more reactive sites and Fe²⁺ ions. Acidic pH values favorited the 4-CP removal due to the high H⁺ concentrations, while Alkaline pH value inhabited the 4-CP removal. A higher temperature increased the rate of •OH formation and enhanced the 4-CP removal percentage. At a fixed dosage of the ZVI/EG-2, the ratio of available reactive sites was less at higher initial concentrations. These results prove the possibility of synthesizing high active and stable ZVI/EG catalysts using graphite from spent LIB and ferric chloride. These catalysts show promising prospective for the 4-CP removal in water, with comparable activities to others previously reported.

Enhanced antibiotic degradation and hydrogen production of deacetoxycephalosporin C fermentation residue by gamma radiation coupled with nano zero-valent iron

Antibiotic fermentation residue (AFR) has been categorized as hazardous waste in China. Anaerobic biohydrogen fermentation may be a promising technology for handling AFR, which could achieve dual goals of waste treatment and clean energy production at the same time. However, the low hydrogen yield and low removal efficiency of residual antibiotics are two major factors limiting the AFR biohydrogen fermentation process. This work firstly applied gamma radiation (50 kGy) to remove the residual antibiotic in AFR and improve the bioavailability of organic matters, then adding nano zero-valent iron (nZVI) (100-1000 mg/L) to further enhance the AFR biohydrogen fermentation performance. Results showed that residual deacetoxycephalosporin C in AFR was removed with a high efficiency of 98.6%, and hydrogen yield achieved 20.45 mL/g-VS_added with the combined approach of gamma radiation pretreatment and 500 mg/L nZVI addition, which was 139.2% higher compared to the control experimental result. The combined approach also promoted the biohydrogen production rate, decreased the lag phase of hydrogen production, and increased the organics utilization. Microbiological analysis revealed that highly efficient hydrogen-producing genera Clostridium sensu stricto were enriched in much higher abundance with the combined approach, which might be the fundamental mechanism for the enhanced AFR fermentation performance.

Waste expanded polystyrene modified with H2SO4/biodegradable chelating agent for reuse: As a highly efficient adsorbent to remove fluoroquinolone antibiotic from water

Untreated wastewater containing fluoroquinolone antibiotics poses serious hazards to aquatic species and human health; therefore, treatment of waste expanded polystyrene (EPS) is a crucial environmental matter. In this study, waste EPS was modified with a H₂SO₄/biodegradable chelating agent, [S,S]-ethylenediamine-N,N'-disuccinic acid (EDDS), and used for highly efficient adsorption of the fluoroquinolone antibiotic ciprofloxacin. When ciprofloxacin of 25 mg/L was used, the H₂SO₄-modified EPS (EPS_H2SO4) adsorbed 60.5% of the ciprofloxacin. During sulfonation, adding a low dose of EDDS markedly improved the adsorption ability of EPS_H2SO4+EDDS. The optimal modification conditions were 95% H₂SO₄, 0.002 M EDDS, 80 °C, and 40 min. The increased adsorbent doses enhanced the adsorption. Approximately 0.2 g/L of EPS_H2SO4+EDDS could effectively adsorb 97.8% of the ciprofloxacin (554.3 mg/g) within 30 min. Solution pH₀ greatly influenced the adsorption, and the most suitable pH₀ was 6. The Langmuir isotherm accurately described the adsorption behaviors of both EPS_H2SO4 and EPS_H2SO4+EDDS (R² = 0.997-0.998). The adsorption ability of EPS_H2SO4+EDDS (q_max = 1250 mg/g) was 32 times higher than that of EPS_H2SO4 (q_max = 38.6 mg/g). A total of 1 M HCl effectively regenerated the exhausted adsorbent. The optimal solid/liquid ratio and time were 0.08 g/20 mL and 60 min, respectively. The regenerated EPS_H2SO4+EDDS maintained a high adsorption ability (87.2%) after 10 regeneration cycles. The results thus indicate that the EPS_H2SO4+EDDS adsorption-regeneration process is a potential approach to remove ciprofloxacin from water.