Effects of PMMA/anisole hybrid coatings on discoloration performance of nano zerovalent iron toward organic dyes

Exploring the Impact of Surface Functionalization on the Reaction, Magnetophoretic, and Collective Transport Behavior of Nanoscale Zerovalent Iron

This study provides a systematic analysis of the transport and magnetophoretic behavior of nanoscale zerovalent iron (nZVI) particles, both bare and surface functionalized by poly(ethylene glycol) (PEG) and carboxymethyl cellulose (CMC), after undergoing a chemical reaction. Here, a simple and well-investigated chemical reaction of methyl orange (MO) degradation by nZVI was used as a model reaction system, and the sand column transport and low-gradient magnetophoretic profiles of the nanoparticles were measured before and after the reaction. The results were compared over time and analyzed in the context of extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to understand the particle interactions involved. The colloidal stability of both bare and functionalized nZVI particles was enhanced after the reaction due to the consumption of metallic Fe content, resulting in a significant drop in their magnetic properties. As a result, they exhibited improved mobility across the sand column and a slower magnetophoretic collection rate compared to the unreacted particles. Here, the colloidal filtration theory (CFT) was employed to analyze the transport behavior of nZVI particles across the packed sand column. It has been observed that the surface properties of the reacted functionalized particles changed, possibly due to the entrapment of degraded products within the polymer adlayer. Moreover, quartz crystal microbalance with dissipation (QCM-D) measurements were performed to reveal the viscoelastic contribution of the adlayer formed by both bare and functionalized nZVI particles after the reaction on influencing their transport behavior across the sand column. Finally, we proposed the implementation of a high-gradient magnetic trap (HGMT) to reduce the transport distance of the colloidally stable CMC-nZVI, both before and after the reaction. This study sheds light on the behavioral changes of iron nanoparticles after the reaction and highlights environmental concerns regarding the presence of reacted nanoparticles.

Novel synthesis of aluminum hydroxide gel-coated nano zero-valent iron and studies of its activity in flocculation-enhanced removal of tetracycline

A newly designed aluminum hydroxide gel-coated nanoscale zero-valent iron (AHG@NZVI) with enhanced activity and dispersibility of NZVI was successfully synthesized. The AHG@NZVI composite was synthesized via control of the surface AHG content. AHG@NZVI-1, AHG@NZVI-2 and AHG@NZVI-3 were prepared under centrifugal mixing speeds of 1000, 2000 and 4000 r/min, respectively. The activity of AHG@NZVI was evaluated by its tetracycline (TC) removal efficiency. The effects of AHG content, pH value, reaction temperature, and presence of competitive anions on TC removal were investigated. TC could be removed by both adsorption and chemical reduction on AHG@NZVI-2 (centrifugal speed 2000 r/min) in a short time with high removal efficiency (≥98.1%) at the optimal conditions. Such excellent performance can be attributed to a synergistic interaction between aluminum hydroxide gel and NZVI: (1) AHG could enhance the stability and dispersity of NZVI; (2) aluminum hydroxide gel could absorb a certain amount of TC and Fe²⁺/Fe³⁺, which facilitated the mass transfer of TC onto the NZVI surface, resulting in acceleration of the reduction rate of TC by the AHG@NZVI composite; and (3) AHG-Fe²⁺/Fe³⁺ could absorb a certain amount of TC by flocculation. The kinetics of TC removal by AHG@NZVI composite was found to follow a two-parameter pseudo-first-order model. The presence of competitive anions slightly inhibited the activity of AHG@NZVI systems for TC removal. Overall, this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.

Biochar-supported nZVI (nZVI/BC) for contaminant removal from soil and water: A critical review

The promising characteristics of nanoscale zero-valent iron (nZVI) have not been fully exploited owing to intrinsic limitations. Carbon-enriched biochar (BC) has been widely used to overcome the limitations of nZVI and improve its reaction with environmental pollutants. This work reviews the preparation of nZVI/BC nanocomposites; the effects of BC as a supporting matrix on the nZVI crystallite size, dispersion, and oxidation and electron transfer capacity; and its interaction mechanisms with contaminants. The literature review suggests that the properties and preparation conditions of BC (e.g., pore structure, functional groups, feedstock composition, and pyrogenic temperature) play important roles in the manipulation of nZVI properties. This review discusses the interactions of nZVI/BC composites with heavy metals, nitrates, and organic compounds in soil and water. Overall, BC contributes to the removal of contaminants because it can attenuate contaminants on the surface of nZVI/BC; it also enhances electron transfer from nZVI to target contaminants owing to its good electrical conductivity and improves the crystallite size and dispersion of nZVI. This review is intended to provide insights into methods of optimizing nZVI/BC synthesis and maximizing the efficiency of nZVI in environmental cleanup.

Iron nanoparticles in capsules: derived from mesoporous silica-protected Prussian blue microcubes for efficient selenium removal

A “simultaneous removal–recovery” strategy for pollutants is realized by using Fe/C@mSiO₂ capsules.

Remediation of trichloroethylene-contaminated groundwater by three modifier-coated microscale zero-valent iron

Building a microscale zero-valent iron (mZVI) reaction zone is a promising in situ remediation technology for restoring groundwater contaminated by trichloroethylene (TCE). In order to determine a suitable modifier that could not only overcome gravity sedimentation of mZVI but also improve its remediation efficiency for TCE, the three biopolymers xanthan gum (XG), guargum (GG), and carboxymethyl cellulose (CMC) were employed to coat mZVI for surface modification. The suspension stability of the modified mZVI and its TCE removal efficiency were systematically investigated. The result indicated that XG as a shear-thinning fluid showed the most remarkable efficiency of preventing mZVI from gravity sedimentation and enhancing the TCE removal efficiency by mZVI. In a 480-h experiment, the presence of XG (3 g L(-1)) increased the TCE removal efficiency by 31.85 %, whereas GG (3 g L(-1)) and CMC (3 g L(-1)) merely increased by 15.61 and 9.69 % respectively. The pH value, Eh value, and concentration of ferrous ion as functions of the reaction time were recorded in all the reaction systems, which indicated that XG worked best in buffering the pH value of the solution and inhibiting surface passivation of mZVI.

Removal of bisphenol A by iron nanoparticle-doped magnetic ordered mesoporous carbon

Iron nanoparticle-doped magnetic ordered mesoporous carbon (Fe/OMC) was prepared by co-impregnation and carbothermal reduction methods, and used for highly effective adsorption and degradation of bisphenol A (BPA).

Carriers for nano zerovalent iron (nZVI): synthesis, application and efficiency

An in-depth study accessing all possible carriers used for the synthesis of nZVI and their effect on pollution remediation.