Using resin supported nano zero-valent iron particles for decoloration of Acid Blue 113 azo dye solution

Synergetic effect of green synthesized NZVI@Chitin-modified ZSM-5 for efficient oxidative degradation of tetracycline

The aggregation and limited activity of nanoscale zero-valent iron (NZVI) in aqueous media hinder its practical application. In this study, a cost-effective, environmentally friendly, robust, and efficient synthesis method for NZVI-based composite was developed. NZVI@Chitin-modified ZSM-5 (NZVI@C-ZSM) composite was facilely and greenly synthesized by loading NZVI into alkali-modified ZSM-5 molecular sieves after modifying with chitin as a surfactant and binder. NZVI@C-ZSM exhibited remarkable efficacy in TC removal, achieving a removal efficiency of 97.72% within 60 min. Compared with pristine NZVI, NZVI@C-ZSM demonstrated twice the removal efficiency, indicating that NZVI@C-ZSM effectively improved the dispersion and stability of NZVI. This enhancement provided more reactive sites for generating reactive oxygen species (ROS), significantly boosting catalytic activity and durability while reducing the potential risk of secondary pollution. An improved two-parameter pseudo-first-order kinetic model was used to effectively characterize the reaction kinetics. The mechanism for TC removal primarily involved an adsorption process and chemical oxidation-reduction reactions induced by hydroxyl radicals (•OH) and superoxide radicals (•O2-). Three potential degradation pathways for TC were suggested. Furthermore, NZVI@C-ZSM exhibited good resistance to interference, suggesting its broad potential for practical applications in complex environmental conditions. This study offers a viable material and method for addressing the issue of antibiotic-contaminated water, with potential applications in water resource management.

Efficient Removal of Ciprofloxacin from Contaminated Water via Polystyrene Anion Exchange Resin with Nanoconfined Zero-Valent Iron

Ciprofloxacin (CIP), an important emerging contaminant, has been frequently detected in water, and its efficient removal has become an issue of great concern. In this study, a nanocomposite material nZVI/PA was synthesized by impregnating nanoscale zero-valent iron (nZVI) inside a millimeter-sized porous host (polystyrene-based anion exchange resin (PA)) for CIP removal. The nZVI/PA composite was characterized by field emission scanning electron microscopy coupled with energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, as well as X-ray photoelectron spectroscopy, and it was confirmed that nZVI was uniformly dispersed in PA with a small particle size. Furthermore, several key factors were investigated including initial solution pH, initial CIP concentration, co-existing ions, organic ligands, and dissolved oxygen. The experimental results indicated that the nZVI/PA composites exhibited a high removal efficiency for CIP under the conditions of initial pH 5.0, and initial CIP concentration 50 mg L^-1 at 25 °C, with the maximum removal rate of CIP reaching 98.5%. Moreover, the nZVI/PA composites exhibited high efficiency even after five cycles. Furthermore, quenching tests and electron spin resonance (ESR) confirmed that CIP degradation was attributed to hydroxyl (·OH) and superoxide radicals (⋅O2-). Finally, the main degradation products of CIP were analyzed, and degradation pathways including the hydroxylation of the quinolone ring, the cleavage of the piperazine ring, and defluorination were proposed. These results are valuable for evaluating the practical application of nZVI/PA composites for the removal of CIP and other fluoroquinolone antibiotics.

Sacrificial Zinc Oxide Strategy-Enhanced Mesoporosity in MIL-53-Derived Iron–Carbon Composite for Methylene Blue Adsorption

MOF-derived carbon-based materials have attracted widespread attention due to their relatively large surface area, morphology, and their stability in water. Considering these advantages, these materials present themselves as excellent adsorbents. In this work, a novel method was designed for the fabrication of a nano zero-valent-iron (nZVI) carbon composite. The utilization of zinc oxide nanorods (ZnONRs) in the role of sacrificial consumable nuclei for the synthesis of MIL-53 sacrificial zinc oxide nanorods (MIL-53-SNR) and the subsequent pyrolysis at 700 °C in the inert atmosphere led to a graphitic-supported nZVI material (Fe-C-SNR). Fe-C-SNR was compared with a commercial zinc oxide bulk (MIL-53-SB) and with a pristine MIL-53. By virtue of the ZnONRs, Fe-C-SNR exhibited a greatly improved mesoporous structure. Consequently, the pyrolyzed materials were applied as adsorbents for methylene blue. Fe-C-SNR’s performance increased to more than double of the pyrolyzed MIL-53 (Fe-C), with a remarkably fast adsorption time (10 min) for a concentration of 10 mg L−1 with only 200 mg L−1 adsorbent required. This functional composite also displayed exceptional recyclability; after ten complete cycles, Fe-C-SNR was still capable of completely adsorbing the methylene blue. The utilization of ZnONRs proves itself advantageous and could further be extended to other MOFs for a wide range of applications.

Mechanistic insight into the adsorption of mercury (II) on the surface of red mud supported nanoscale zero-valent iron composite

Recently, nanoscale zero-valent iron (nZVI) particles have been efficiently used in the remediation of many heavy metals, yet potential agglomeration and loss of nZVI remain a critical area of research. In this study, we used red mud as a stable supporting medium to develop red mud modified nZVI to form (RM-nZVI) composite. We assessed its sorptive/reductive removal of mercury (Hg²⁺) from aqueous solutions. The RM-nZVI was synthesized through the reduction of ferric iron by sodium borohydride (NaBH₄) in the presence of red mud. Morphological characterization of RM-nZVI confirmed its diffusion state with lesser aggregation. The RM-nZVI has the BET surface area, pore diameter, and pore volume as 111.59 m²g^-1, 3.82 nm, and 0.49 cm³g^-1, respectively. Adsorption of mercury (Hg²⁺) by RM-nZVI exhibits pH-dependent behavior with increased removal of Hg²⁺ with the increase in pH up to 5, and the removal rate decreased gradually as the pH increased from 5 to 10. Extensive characterization of RM-nZVI corroborated the evidence that the removal of Hg²⁺ was initially by rapid physical adsorption, followed by a reduction of Hg²⁺ to Hg⁰. The adsorption data were best fitted with Langmuir isotherm with R² (correlation coefficient) > 0.99 with high uptake capacity of 94.58 (mg g^-1). The novel RM-nZVI composite with enhanced sorptive and reductive capacity is an ideal alternative for removing Hg²⁺ from contaminated water.

A systematic review on iron-based nanoparticle-mediated clean-up of textile dyes: challenges and prospects of scale-up technologies

The projected increase of the global textile industry to USD1002.84 billion in 2027 indicates a simultaneous increase in water pollution due to textile dye-rich voluminous effluents highlighting the requirement of source clean-up. This review analyzes the colossal amount of literature on lab-scale nanoremediation technologies involving iron-based nanoparticles and the mechanistic aspects. However, not many studies are in place with regard to execution because there are several bottlenecks in the scale-up of the technology. This review attempts to identify the limitations of scale-up by focusing on each step of nanoremediation from synthesis of iron-based nanoparticles to their applications. The most prominent appears to be the low economic viability of physico-chemical synthesis of nanoparticles, lack of appropriate toxicity studies of iron-based nanoparticles, and dearth of studies on field applications. It is recommended that above studies should be made not only on lab scale but also on field samples preferably utilizing microbial products based green synthesized iron-based nanoparticles and conducting toxicity studies. Besides, immobilization of the nanoparticles on renewable material greatly enhances the sustainability and economic value of the process. Furthermore, since the chemical composition of dye-rich effluents varies among industries, effluent specific optimization of process parameters and kinetics thereof is also a major prerequisite for scale-up. The value of this review lies in the fact that it brings, for the first time, a comprehensive and critical systematization of various aspects needing attention in order to scale-up such effective nanoremediation processes.

Ultrasound-assisted electrodeposition synthesis of nZVI-Pd/AC toward reductive degradation of methylene blue

A novel composite (nZVI/Pd-AC) was prepared by loading nanoscale zero-valent iron (nZVI) and Pd on activated carbon (AC) electrode under electrodeposition with ultrasound, which was used to reductive degradation of methylene blue (MB). The loading contents of Fe and Pd in composite materials were 15.84% and 2.06%, respectively. XPS results further confirmed that the as-prepared material contained Fe0 and Pd0. Without external conditions, MB could be degraded in the presence of nZVI/Pd-AC and reached equilibrium within 180 min. To investigate the reusability, the re-electrodeposition strategy was effective to refresh the active sites of nZVI/Pd-AC, and the removal efficiency only reduced by 4.51% in five circles indicating the good reusability of nZVI/Pd-AC composites. GC-MS was used to identify possible degradation pathways of MB; the results showed that the degradation products were mainly N, N-dimethylaniline and 2-amino-5-dimethylamino-benzenesulfonic acid. And the S-C, C-N bonds are the sites easier to be attacked.

Application of Biochar in Stormwater Treatment: Experimental and Modeling Investigation

This research investigated the removal of heavy metal ions (Cd, Cu, Pb, and Zn) and metalloid (As) common to stormwater runoff onto biochar-based media arranged in multiple configurations. Laboratory scale column experiments were conducted to quantify heavy metal removal efficiencies using sand, biochar, and nZVI-modified biochar (BC-nZVI) in four media configurations: a homogeneous mixture of sand and biochar (BCM); biochar layered in sand (BCL); BC-nZVI layered in sand (BCZ); and sand as a control. An inverse modeling approach was implemented to measured moisture and experimental data to determine media hydraulic parameters (θr, θs, α, n and Ks) and adsorption coefficients. The experiment was conducted using laboratory synthesized stormwater over 200 days at a rate of 5 cm/day. BCZ exhibited an excellent removal (99%) of As due to the high attachment to nZVI, via surface complexations. Biochar with abundant surface oxygen functional groups exhibited a great (99%) removal of Cd and Zn in both BCL and BCM columns. Water contents were observed 66.0, 44.3, 41.4, and 7.2% for BCL, BCM, BCZ, and sand, respectively. The attachment coefficients varied from 21.5 to 44.9, 16.1 to 19.3, 18.8 to 26.0, and 9.6 to 19.9 L/kg for BCL, BCM, BCZ, and sand, respectively. This study’s output provides useful information for stormwater management practices.

Continuous Flow Process for Cr(VI) Removal from Aqueous Solutions Using Resin Supported Zero-Valent Iron

The objective of the present study was to evaluate the performance of a nanocomposite material consisting of nano zero valent iron and a cation exchange resin, for the reduction of chromate, by conducting column tests. A cationic resin, Amberlyst 15, was selected as porous host material. The synthesis of the nanocomposite material (R-nFe) was carried out using Green Tea extract to obtain the reduction of adsorbed Fe(III) to the elemental state Fe(0). Three column tests were implemented with different dimensions, corresponding to variable contact times between the aqueous solution and the resin beads loaded with Fe(0), namely 168, 744 and 1260 s respectively for columns I, II and III. The results indicated that the removal of Cr(VI) follows a first order kinetic law with a chemical constant equal to 0.0526 min^-1 (8.8 × 10^-4 s^-1).

Effects of humic acid on enhanced removal of lead ions by polystyrene-supported nano-Fe (0) nanocomposite

Polymer-supported nanozero-valent iron composites (D001-nZVI) were fabricated for the removal of lead ions from aqueous solutions by embedding nZVI into the porous polystyrene anion exchanger D001. Humic acid (HA) was selected as a model species because of its ubiquitous existence to gain insight into the influencing factors in the actual application process. The iron contents of the composites were approximately 11.2%, and the smallest ZVI particle size was ~ 5 nm. The experimental results showed that the effect of HA on the reduction of lead ions by D001-nZVI was a concentration-dependent process. At low HA concentrations, the surface-competitive adsorption of HA and Pb²⁺ dominated; therefore, the removal efficiency of Pb²⁺ by D001-nZVI decreased from 97.5 to 90.2% with an increasing HA concentration. When the HA concentration increased to 30 mg/L or more, the lead ions removal remained constant with the following possible cooperation mechanism: the competitive adsorption of HA and Pb²⁺ on the nZVI surface and the well-dispersed particles were caused by electrostatic interactions between the HA coating and the nZVI surface. In addition, the adsorption complexation between HA and Pb²⁺ also had a positive effect on the removal of Pb²⁺ at higher concentrations of HA.

Heterogeneous Fenton Degradation of Patulin in Apple Juice Using Carbon-Encapsulated Nano Zero-Valent Iron (CE-nZVI)

Patulin (PAT), a mycotoxin found mainly in matured apples, is produced by different species of fungi, mainly Penicillium expansum, and is found in various fruits and vegetables used to produce juice. Little focus has been placed on nano-technological methods for the mitigation of this problem. In this work, carbon-encapsulated nano-zero valent iron (CE-nZVI) particles were synthesized and used as heterogeneous Fenton agents for the degradation of PAT in apple juice. The particles were found to have a spherical shape with a diameter of 130 ± 50 nm. In a heterogeneous Fenton degradation (involving CE-nZVI) process, a concentration of 0.05 g/L CE-nZVI with 0.5 mM H2O2 was used. Since the Fenton oxidation process is pH-dependent, placebo degradation was observed at varying pH conditions with an average percentage of PAT degradation of 27.8%, 87.0%, 98.0%, and 99.75% at pH 6, 5, 4.5, and 3.5 respectively, between 1 min to 4 h in a water matrix. In a juice matrix, at the regular pH of juice (3.6), percentage PAT degradation of 72% and 89% was obtained after a 2-h treatment using heterogeneous Fenton oxidation (CE-nZVI/H2O2) systems, using 0.5 mM H2O2 and 1 mM H2O2, respectively.

Removal mechanism of mitoxantrone by a green synthesized hybrid reduced graphene oxide @ iron nanoparticles

Anti-tumor drugs, due to their non-specific toxicity will cause long-term delayed toxicity to organisms and humans when discharged into the environment. In this study, reduced graphene oxide @ iron nanoparticles (rGO@Fe NPs) were successfully prepared using green tea extract as reductant and subsequently used for mitoxantrone (MTX) removal. SEM and Raman spectroscopy showed that 30-60 nm sized Fe NPs were loaded on rGO and green tea extract successfully reduced GO to rGO. The removal efficiency of MTX by the hybrid material was higher (98.5%) than either rGO (77.5%) or Fe NPs (53.1%) alone. In addition, the removal efficiency of MTX by the hybrid material was as high as 95% within 5 min, MTX adsorption followed both a pseudo-second-order kinetic model and the Langmuir isotherm, and it is a spontaneous adsorption. Recycling experiments showed that the removal efficiency of MTX decreased from 99.9 to 76.8% after six cycles, and could be as high as 99% in both municipal and medical wastewater. Scanning electron microscopy (SEM), Fourier transform infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and High performance liquid chromatography (HPLC) were all used to characterize and analyze the hybrid material, and possible adsorption mechanisms which revealed that MTX adsorption probably involved a combination of π-π stacking interaction, hydrogen bonding, electrostatic interaction and pore-filling.

Mechanism study of Chromium influenced soil remediated by an uptake-detoxification system using hyperaccumulator, resistant microbe consortium, and nano iron complex

A soil heavy metal decontamination system was developed based on the immobilization of bioavailable metal fraction by iron-biochar nano-complex (BC@Fe₃O₄) and the uptake by Chromium (Cr) hyperaccumulator Leersia hexandra (L. hexandra) under the assistance of metal resistant microbe consortium (MC). In this system, L. hexandra was able to accumulate 485.1-785.0 mg kg^-1 in root and 147.5-297.2 mg kg^-1 of Cr in its aerial part. With MC assistance, more Cr could be translocated to the aerial part of L. hexandra, which dramatically improved its remediation potential. Meanwhile, BC@Fe₃O₄ application decreased bioavailable Cr in soil and reduced soil toxicity, which contributed to soil microbial community adaption and L. hexandra performance under high level of Cr concentration (elevated microbial activity, decreased plant stress response, enhanced L. hexandra growth and accumulation) without negative influence on accumulation efficiency. Moreover, details of the possible mechanistic insight into metal removal were discussed, which indicated a negative correlation of the extractable Cr with soil microecology and hyperaccumulator performance. Furthermore, the resistant bacteria successfully altered soil microbial community, enhanced its diversity, which was in favor of the soil quality improvement.

Rice Husk Biochars Modified with Magnetized Iron Oxides and Nano Zero Valent Iron for Decolorization of Dyeing Wastewater

This study investigated if biochar, a low-cost carbon-rich material, can be modified with reactive materials for decolorization of dyeing wastewater. Two types of rice husk biochars were produced by using different processes of gasification and pyrolysis in limited air condition. The biochars were first magnetized and then modified with nano-scale zero-valent iron (nZVI) to achieve the final products of magnetic-nZVI biochars. Batch experiments were conducted to investigate the efficiency of the modified biochars for reducing color of the reactive dyes yellow (RY145), red (RR195), and blue (RB19) from dyeing solutions. Results showed that color removal efficiency of the modified biochars was significantly enhanced, achieving the values of 100% for RY145 and RR195 and ≥65% for RB19, while the effectiveness of the original biochar was significantly lower. In addition, with increasing dose of the modified biochars, the color removal efficiency increased accordingly. In contrast, when the dose of nZVI was increased beyond a certain value then its color removal efficiency decreased accordingly. It is reported that the magnetic-nZVI rice husk biochars effectively removed the reactive dyes. The impregnation of nZVI particles on the biochar surface spatially separates the nZVI particles, prevents its aggregation and therefore enhances the decolorization efficiency.

Persulfate activation by natural zeolite supported nanoscale zero-valent iron for trichloroethylene degradation in groundwater

In the advanced oxidation processes, using persulfate (PS) as a radical precursor for pollutant degradation in groundwater has received increasing attention. In this study, zeolite supported nZVI composites (Z/nZVI) were synthesized through an ion exchange and borohydride reduction method to investigate their ability to activate PS for the TCE degradation. Based on preliminary screening of the PS activation by the Z/nZVI (PS-Z/nZVI) system in terms of TCE degradation, Z/nZVI composite with a zeolite to nZVI mass ratio of 1:1 (Z/nZVI (1)) was optimized as the best composition and chosen for further characterization and examination. Especially, for this PS-Z/nZVI system, PS concentration, solution matrix effects (i.e., solution pH, coexisting anions and natural organic matter) were studied. Characterization results revealed that the aggregation of nZVI particles was alleviated and they were good dispersed on the zeolite sheet with a large SSA (159.49 m²/g) compared to the unsupported nZVI (8.77 m²/g). The synthesized Z/nZVI (1) composite exhibited excellent activated ability towards PS (1.5 mM) and effectively degraded 98.8% of TCE at pH 7 within 120 min. The PS-Z/nZVI system was observed to operate effectively over a wide range of pH (i.e., 4-7) for TCE degradation. Moreover, the presence of nitrates (1 mM) and bicarbonates (10 mM) decreased the TCE degradation efficiency to 91.5% and 59.6%, respectively. Scavenger tests demonstrated that both sulfate and hydroxyl radicals participated in the TCE degradation. The ion chromatography analysis suggested the formation of oxalic acid and formic acid as the reaction intermediates during the TCE degradation process in the PS-Z/nZVI system.

Optimization of Photocatalytic Degradation of Acid Blue 113 and Acid Red 88 Textile Dyes in a UV-C/TiO2 Suspension System: Application of Response Surface Methodology (RSM)

Textile industries produce copious amounts of colored wastewater some of which are toxic to humans and aquatic biota. This study investigates optimization of a bench-scale UV-C photocatalytic process using a TiO2 catalyst suspension for degradation of two textile dyes, Acid Blue 113 (AB 113) and Acid Red 88 (AR 88). From preliminary experiments, appropriate ranges for experimental factors including reaction time, solution pH, initial dye concentration and catalyst dose, were determined for each dye. Response surface methodology (RSM) using a cubic IV optimal design was then used to design the experiments and optimize the process. Analysis of variance (ANOVA) was employed to determine significance of experimental factors and their interactions. Results revealed that among the studied factors, solution pH and initial dye concentration had the strongest effects on degradation rates of AB 113 and AR 88, respectively. Least-squares cubic regression models were generated by step-wise elimination of non-significant (p-value > 0.05) terms from the proposed model. Under optimum treatment conditions, removal efficiencies reached 98.7% for AB 113 and 99.6% for AR 88. Kinetic studies showed that a first-order kinetic model could best describe degradation data for both dyes, with degradation rate constants of k1, AB 113 = 0.048 min−1 and k1, AR 88 = 0.059 min−1.

Highly efficient immobilization of NZVI onto bio-inspired reagents functionalized polyacrylonitrile membrane for Cr(VI) reduction

To provide superior substrates and determine the specific species of immobilized nano zero-valent iron (NZVI) system, polyacrylonitrile (PAN) membrane was functionalized by bio-inspired polydopamine (PDA) and poly(_l-DOPA) (PDOPA) for efficient immobilization of NZVI. The synthesized composites were denoted as PAN/PDA-NZVI (PPN) and PAN/PDOPA-NZVI (PON), respectively. Analyses of XRD, SEM/EDS and XPS show that the aggregation and release of iron nanoparticles had been successfully controlled by improving membrane hydrophilcity and iron-chelating capacity via the graft of functionalized groups (i.e. OH and COOH) of PDA and PDOPA on PAN membrane. Both PPN and PON composites exhibited superior reactivity for Cr(VI) removal (Cr(VI) removal efficiency and reaction rate were 2.21-2.22 and 9.90-10.14 times higher than that of bare NZVI, respectively). The stability and recyclability of PPN and PON composites could be maintained over repeated cycles. Further analyses indicate that PON is more capable for Cr(VI) elimination than PPN due to the proprietary carboxyl of _l-DOPA. With the addition of 1,10-phenanthroline, membrane-chelated Fe(II) was determined to be the major species in Cr(VI) removal system, accounting for 56.9% and 53.8% with regard to PPN and PON composites, and Fe⁰ was responsible for the reduction of residual Cr(VI). Analyse of reacted composites revealed that Cr(VI) was completely converted into Cr(III), followed by formation of dominant Cr(III)/Fe(III) (oxy)hydroxides and partial desorption from NZVI reactive sites. This study suggested that both synthesized PPN and PON composites have potentials for Cr(VI)-contaminated wastewater treatment.

Removal of multiple nitrosamines from aqueous solution by nanoscale zero-valent iron supported on granular activated carbon: Influencing factors and reaction mechanism

Due to their significant absorption and reduction abilities, nanoscale zero-valent iron (nZVI)/granular activated carbon (GAC) composites are very effective for the degradation of organic contaminants and heavy metals. However, to date, there is no systematic study on the applicability of nZVI/GAC for the removal of multiple highly toxic nitrosamines from water supplies. For this study, nZVI/GAC was synthesized and applied to the degradation of multiple nitrosamines. The effects of initial nitrosamine concentration, composite dosage, contact duration, competition with coexistent elements, and reaction mechanisms during the nitrosamine removal process from aqueous solutions were investigated. Compared with bare nZVI and GAC, the removal rates of six nitrosamines via nZVI/GAC were initially very rapid. The highest removal ratios of the six nitrosamines were 76.1% (N-nitrosodimethylamine, NDMA), 84.7% (N-nitrosomethylethylamine, NMEA), 89.8% (N-nitrosodiethylamine, NDEA), 93.5% (N-nitrosodi-n-propylamine, NDPA), 95.7% (N-nitrosodi-n-butylamine, NDBA), and 80.4% (N-nitrosomorpholine, NMor). The nitrosamine degradation kinetics data agreed well with the pseudo-second-order model (R₂² > 0.99), the rate constant k₂ for nitrosamine (200 ng/L) removal by nZVI/GAC increased in the order of NDBA (0.3675) > NDPA (0.0254) > NMEA (0.0109) > NDEA (0.0105) > NDMA (0.0101) > NMor (0.0077). In the presence of cations, anions, and humic acid (HA) the removal of the six nitrosamines was inhibited at each concentration. Furthermore, the removal ratios and K₂ of the five linear nitrosamines by nZVI/GAC partially scaled with structure, LogK_ow, and Henry's constant, particularly between K₂ and these properties (R² > 0.80). The reaction mechanism revealed that nitrosamines were adsorbed by GAC and then reduced by Fe⁰, where the reductive products were primarily secondary amines, nitrate, and nitrite. This study serves to improve our understanding, and further characterizes the removal of multiple nitrosamines by nZVI/GAC.

Dynamic study of Cr(VI) removal performance and mechanism from water using multilayer material coated nanoscale zerovalent iron

In this study, the dynamic Cr(VI) removal process from water by the synthesized multilayer material coated nanoscale zerovalent iron (SBC-nZVI) was systematically discussed at different treatment conditions. The results showed that initial pH, contact time, Cr(VI) concentration and the dosage of SBC-nZVI were important parameters that influenced the Cr(VI) removal efficiency. The major Cr(VI) removal occurred within 60 min and gradually tend to equilibrium with consistent treatment. The removal efficiency was highly depended on pH values and the adsorption kinetics agreed well with the pseduo-second-order model (PSO). When the initial Cr(VI) concentration was below 15 mg/L, the removal rate could reach to about 100%. Moreover, the removal efficiency increased with the increase of SBC-nZVI dosage, which related to the increase of reactive sites. To understand the removal mechanism, SBC-nZVI before and after reaction with Cr(VI) were characterized by fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). These analysis showed that the interaction of SBC-nZVI with Cr(VI) was mainly controlled by reduction and electrostatic attraction. Therefore, these results explained the interaction between Cr(VI) and SBC-nZVI material in detail, and further proved that SBC-nZVI could be an effective material to remove Cr(VI) from water.

Biochar supported sulfide-modified nanoscale zero-valent iron for the reduction of nitrobenzene

Sulfide-modified nanoscale zerovalent iron (S-nZVI) was effectively utilized for the reduction of various contaminants, despite its applicability being limited due to agglomeration, oxidation and electron loss. In this study, biochar (BC)-supported S-nZVI was prepared to enhance the reactivity of S-nZVI for nitrobenzene (NB) reduction. Scanning electron microscopy images showed that the S-nZVI particles were well-dispersed on the BC surface as well as in the channels. NB removal and aniline formation could be significantly enhanced by using S-nZVI@BC, as compared to S-nZVI and blank BC. NB removal by S-nZVI@BC followed the pseudo second-order kinetics model and Langmuir isotherm model, suggesting hybrid chemical reaction-sorption was involved. Furthermore, a possible reaction mechanism for enhanced NB removal by S-nZVI@BC was proposed, including chemical adsorption of NB onto S-nZVI@BC, direct reduction by S-nZVI and enhanced electron transfer. The high reducibility of S-nZVI@BC as well as its excellent antioxidation ability and reusability demonstrated its promising prospects in remediation applications.

Simultaneous removal of amoxicillin, ampicillin and penicillin by clay supported Fe/Ni bimetallic nanoparticles

This study examined functional bentonite-supported nanoscale Fe/Ni (B-Fe/Ni) for the simultaneous removal of β-lactam antibiotics such as amoxicillin (AMX), ampicillin (AMP) and penicillin (PEN). The results show only 94.6% of AMX, 80.6% of AMP and 53.7% of PEN were removed in the mixed antibiotic solution, while 97.5% of AMX, 85.1% of AMP and 74.5% of PEN were removed in individual antibiotic solution. The decreased removal in a mixed antibiotic solution was attributed to competition between antibiotics for: firstly, active sites of iron oxide for the adsorption; and secondly, accepted electrons for the degradation in passivation of the nZVI surface. These were confirmed by various characterization techniques. Kinetics studies of mixed antibiotics using B-Fe/Ni confirmed that adsorption and degradation occurred simultaneously as removing of antibiotics in the presence of particles. Furthermore, the stability and durability of B-Fe/Ni applied to remove β-lactam antibiotics was demonstrated. Finally, B-Fe/Ni was used to reduce the concentration of mixed antibiotics from pharmaceutical wastewater, which indicated B-Fe/Ni is a promising material for antibiotics wastewater treatment.

Nitrobenzene reduction using nanoscale zero-valent iron supported by polystyrene microspheres with different surface functional groups

Three polystyrene (PS) resin microspheres supported nanoscale zero-valent iron (nZVI), i.e., nZVI@PS, nZVI@PS-Cl, and nZVI@PS-N, were prepared and characterized by FT-IR, XPS, SEM, EDS, and weighing method. The functional groups on the carriers showed obvious influence on the loading quantity, the micro morphology, and the reduction efficiency of these supported nZVI. The best hybrid reducer was nZVI@PS-N. The load quantity of nZVI was 0.2476 g/g, and some of them were dispersed and the others remained as particles (≤ 50 nm). At optimal reaction conditions, i.e., initial solution pH = 3, 25 °C, 100 r/min stirring, 99% nitrobenzene (NB) in 250 mL 123.1 mg/L NB solution could be totally reduced into AN by 1.31 g fresh nZVI@PS-N within 20 min. The excellent reduction efficiency and fast degradation rate of nZVI@PS-N were mainly attributed to the synergistic effects between the good adsorption property of its carrier and the high reduction activity of nZVI particles. NZVI@PS-N was reproducible and recycled, and 90.6% degradation ratio of NB was till obtained at its seventh recycle. The results showed that nZVI@PS-N had high potential practical application value in the reductive degradation and emergency rescue of nitrobenzene pollutant.

From nZVI to SNCs: development of a better material for pollutant removal in water

Nanoscale zero-valent iron (nZVI), with its reductive potentials and wide availability, offers degradative remediation for environmental pollutants. However, weaknesses such as easy aggregation, easy oxidation, and nanoscale size have hindered its further applications in the environment to some extent. Therefore, various supported nZVI composites (SNCs) with higher dispersibility, enhanced water stability, and tunable size have been developed to overcome the weaknesses. SNCs family is a great alternative for water purification applications that require high removal efficiency and rapid kinetics, as a result of their multifunctional properties and magnetic separation capacity. In this review, we compare the advantages of SNCs to nZVI for pollutant removal in water, discuss for the first time the synthetic techniques of obtaining SNCs, and analyze the influencing factors and mechanisms associated with the removal of some typical hazardous pollutants (e.g., dyes, heavy metals, nitrogen, and phosphorus) using SNCs. Moreover, limitations and future research needs of such material are discussed. More attention should be paid to the evaluation of toxicity, development of green synthetic routes, and potential application areas of such materials in future research.

Macroscopic and microscopic investigation of uranium elimination by Ca–Mg–Al-layered double hydroxide supported nanoscale zero valent iron

Ca–Mg–Al-LDH/nZVI nanocomposites showed excellent U(vi) removal performance from aqueous solutions through the coordination of reduction and adsorption reactions.

Rapid decoloration of azo dye Direct Blue 6 by AlCrFeMn high entropy alloy

In recent years, high entropy alloys (HEAs) have attracted a lot of attention from researchers due to their outstanding mechanical properties, but there are few reports about their functional performance.

Synthesis, Characterization and Reactivity of Nanostructured Zero-Valent Iron Particles for Degradation of Azo Dyes

Nanostructured zero-valent iron (NSZVI) particles were synthesized by the method of ferric ion reduction with sodium borohydride with subsequent drying and passivation at room temperature in technical grade nitrogen. The obtained sample was characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering studies. The prepared NSZVI particles represent 100–200[Formula: see text]nm aggregates, which consist of 20–30[Formula: see text]nm iron nanoparticles in zero-valent oxidation state covered by thin oxide shell. The reactivity of the NSZVI sample, as the removal efficiency of refractory azo dyes, was investigated in this study. Two azo dye compounds, namely, orange G and methyl orange, are commonly detected in waste water of textile production. Experimental variables such as NSZVI dosage, initial dye concentration and solution pH were investigated. The kinetic rates of degradation of both dyes by NSZVI increased with the decrease of solution pH from 10 to 3 and with the increase of NSZVI dosage, but decreased with the increase of initial dye concentration. The removal efficiencies achieved for both orange G and methyl orange were higher than 90% after 80[Formula: see text]min of treatment.

Removal of chromium (VI) from water using nanoscale zerovalent iron particles supported on herb-residue biochar

A composite material consisting of nanoscale zerovalent iron particles supported on herb-residue biochar (nZVI/BC) was synthesized and used for treatment of Cr(VI)-contaminated water. The effects of initial pH, chromium concentration, contact time, and competition with coexisting anions and natural organic matter (NOM) were also investigated. nZVI/BC was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy analysis (SEM), and the Brunauer-Emmett-Teller surface area was measured. TEM and X-ray photoelectron spectroscopy (XPS) analysis before and after reaction with Cr(VI) showed that reduction and coprecipitation occurred during hexavalent chromium adsorption. The removal of Cr(VI) was highly pH-dependent and the adsorption kinetics data agreed well with the pseudo-second-order model. The presence of SO₄^2- and humic acid promoted Cr(VI) removal at both low and high concentrations, while the HCO₃^- inhibited the reaction. These results prove that nZVI/BC can be an effective reagent for removal of Cr(VI) from solutions.

Synthesis of polyaniline nanoparticles and their application for the removal of Crystal Violet dye by ultrasonicated adsorption process based on Response Surface Methodology

The present study focuses the synthesis of polyaniline nanoparticles (PANP) by rapid mixing polymerization method. They were recognized by FTIR and SEM techniques. Moreover they were utilized for the removal of Crystal Violet (CV) dye by ultrasonicated adsorption process. It ensures a quick alternative method compared to other conventional processes, which led to enhancement of mass transfer by ultrasound waves. The effectiveness of the process was confirmed through the effect of certain conditions like sonication time, temperature, adsorbent dosage and CV concentrations. The validity of the process was estimated by various adsorption isotherms. Kinetics and thermodynamic studies was also conducted to authenticate the process. The optimum operating parameters (OOP) were evaluated by Response Surface Methodology (RSM) based on central composite design (CCD) for the removal of CV dye. Moreover analysis of variances (ANOVA) was employed to estimate the significance of experimental variables. The predicated removal efficiency was found to be 94.29% which prove to be effectiveness of the process.

Effect of solvent on debromination of decabromodiphenyl ether by Ni/Fe nanoparticles and nano zero-valent iron particles

Nano zero-valent iron (nZVI) and its modified nanomaterials are widely used in the degradation of some halogenated organic pollutants. In this study, we explored the effects of different proportions of tetrahydrofuran (THF) (50, 60, 70, 80, 90, and 100 %) on the degradation of decabromodiphenyl ether (BDE209) by Ni/Fe and nZVI nanoparticles with reference to the degradation kinetics, products, and pathway. The results illustrated that the effects of solvent on the degradation of BDE209 were similar when the two kinds of nanomaterials were used, although the Ni/Fe bimetallic nanoparticles exhibited a better catalytic activity compared with the pure nZVI during the degradation of BDE209. The apparent reaction rate constant (k _obs) increased with the proportion of the water in the system, enhancing the degradation of BDE209. In terms of degradation products, a high proportion of THF led to an accumulation of higher-brominated BDEs, inhibiting the further debromination of BDE209. The inhibitory effect of the solvent (THF) can be explained that water played a role of hydrogen donor during the reductive degradation of BDE209 in the THF/water system. However, the proportion of THF in the degradation system posed no effect on the BDE209 debromination pathway and debromination location. The difficulty of para-debromination was observed in all of the solvent systems.

Photodegradation of Orange II using waste paper sludge-derived heterogeneous catalyst in the presence of oxalate under ultraviolet light emitting diode irradiation

A waste paper sludge-derived heterogeneous catalyst (WPS-Fe-350) was synthesized via a facile method and successfully applied for the degradation of Orange II in the presence of oxalic acid under the illumination of ultraviolet light emitting diode (UV-LED) Powder X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electronic microscopy and N2 sorption isotherm analysis indicated the formation of α-Fe2O3 in the mesoporous nanocomposite. The degradation test showed that WPS-Fe-350 exhibited rapid Orange II (OII) degradation and mineralization in the presence of oxalic acid under the illumination of UV-LED. The effects of pH, oxalic acid concentration and dosage of the catalyst on the degradation of OII were evaluated, respectively. Under the optimal conditions (1g/L catalyst dosage, 2mmol/L oxalic acid and pH3.0), the degradation percentage for a solution containing 30mg/L OII reached 83.4% under illumination by UV-LED for 80min. Moreover, five cyclic tests for OII degradation suggested that WPS-Fe-350 exhibited excellent stability of catalytic activity. Hence, this study provides an alternative environmentally friendly way to reuse waste paper sludge and an effective and economically viable method for degradation of azo dyes and other refractory organic pollutants in water.

Characterization of bimetallic Fe/Pd nanoparticles by grape leaf aqueous extract and identification of active biomolecules involved in the synthesis

This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC-MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs.

Removal of Cr(VI) from Water Using a New Reactive Material: Magnesium Oxide Supported Nanoscale Zero-Valent Iron

The chromium pollution of water is an important environmental and health issue. Cr(VI) removal by means of metallic iron is an attractive method. Specifically, nanoscopic zero valent iron (NZVI) shows great reactivity, however, its applicability needs to be further investigated. In the present paper, NZVI was supported on MgO grains to facilitate the treatments for remediation of chromium-contaminated waters. The performances and mechanisms of the developed composite, in the removal of hexavalent chromium, were investigated by means of batch and continuous tests. Kinetic studies, under different operating conditions, showed that reduction of Cr(VI) could be expressed by a pseudo second-order reaction kinetic. The reaction rate increased with the square of Fe(0) amount, while it was inversely proportional to the initial chromium concentration. The process performance was satisfactory also under uncontrolled pH, and a limited influence of temperature was observed. The reactive material was efficiently reusable for many cycles without any regeneration treatment. The performances in continuous tests were close to 97% for about 80 pore volume of reactive material.

Environmental Remediation and Application of Nanoscale Zero-Valent Iron and Its Composites for the Removal of Heavy Metal Ions: A Review

The presence of heavy metals in the industrial effluents has recently been a challenging issue for human health. Efficient removal of heavy metal ions from environment is one of the most important issues from biological and environmental point of view, and many studies have been devoted to investigate the environmental behavior of nanoscale zerovalent iron (NZVI) for the removal of toxic heavy metal ions, present both in the surface and underground wastewater. The aim of this review is to show the excellent removal capacity and environmental remediation of NZVI-based materials for various heavy metal ions. A new look on NZVI-based materials (e.g., modified or matrix-supported NZVI materials) and possible interaction mechanism (e.g., adsorption, reduction and oxidation) and the latest environmental application. The effects of various environmental conditions (e.g., pH, temperature, coexisting oxy-anions and cations) and potential problems for the removal of heavy metal ions on NZVI-based materials with the DFT theoretical calculations and EXAFS technology are discussed. Research shows that NZVI-based materials have satisfactory removal capacities for heavy metal ions and play an important role in the environmental pollution cleanup. Possible improvement of NZVI-based materials and potential areas for future applications in environment remediation are also proposed.

Textile dye degradation using nano zero valent iron: A review

Water soluble unfixed dyes and inorganic salts are the major pollutants in textile dyeing industry wastewater. Existing treatment methods fail to degrade textile dyes and have limitations too. The inadequate treatment of textile dyeing wastewater is a major concern when effluent is directly discharged into the nearby environment. Long term disposal threatens the environment, which needs reclamation. This article reviews the current knowledge of nano zero valent iron (nZVI) technique in the degradation of textile dyes. The application of nZVI on textile dye degradation is receiving great attention in the recent years because nZVI particles are highly reactive towards the pollutant, less toxic, and economical. The nZVI particles aggregate quickly with respect to time and the addition of supports such as resin, nickel, zinc, bentonite, biopolymer, kaolin, rectorite, nickel-montmorillonite, bamboo, cellulose, biochar, graphene, and clinoptilolite enhanced the stability of iron nanoparticles. Inclusion of supports may in turn introduce additional toxic pollutants, hence green supports are recommended. The majority of investigations concluded dye color removal as textile dye compound removal, which is not factual. Very few studies monitored the removal of total organic carbon and observed the products formed. The results revealed that partial mineralization of the textile dye compound was achieved. Instead of stand alone technique, nZVI can be integrated with other suitable technique to achieve complete degradation of textile dye and also to treat multiple pollutants in the real textile dyeing wastewater. It is highly recommended to perform more bench-scale and pilot-scale studies to apply this technique to the textile effluent contaminated sites.