Search

The rapid evolution of antimicrobial resistant genes (AMRs) in water resources is well correlated to the persistent occurrence of ciprofloxacin in water. For the first time, encapsulated nanoscale zerovalent iron (nZVI) with a shell of magnesium hydroxide (Mg/Fe0) was used to adsorb ciprofloxacin from water. Optimization of the removal conditions exhibited that 5% was the optimum mass ratio between magnesium hydroxide and nZVI [Mg(OH)2/nZVI)] as more than 96% of 100 mg L−1 of ciprofloxacin was removed. In addition, 0.5 g L−1 of Mg/Fe0 showed an extraordinary performance in removing ciprofloxacin over a wide range of pH (3–11) with removal efficiencies exceeded 90%. Kinetic analysis displayed that the kinetic data was well described by both Pseudo first-order and second-order models. Also, the equilibrium data was well fitted by Freundlich isotherm model. In addition, thermodynamic analysis evidenced that the removal of ciprofloxacin by Mg/Fe0 was exothermic, and spontaneous. The experiments also revealed that physisorption and chemisorption were the responsible mechanisms for ciprofloxacin removal. The proposed treatment system remediated 10 litters of 100 mg L−1 of ciprofloxacin solution with 100% overall removal efficiency. This treatment system could be a promising and practical solution to decrease ciprofloxacin concentration in different water bodies.

Ciprofloxacin is a fluoroquinolone antibiotic developed to fightback several bacterial diseases. The widespread application in human and animal medicine and the low biodegradation resulted in the persistent detection of ciprofloxacin in many water systems. The occurrence of ciprofloxacin threats human and aquatic life by motivating the development of antimicrobial resistant geneses in water. Microscale (ZVI) and nanoscale zerovalent iron (nZVI) were used to efficiently remove ciprofloxacin from aqueous solutions. The aim of this mini review to summarize: (1) the possible routes for ciprofloxacin to enter the environment, (2) the mechanism of oxidizing organic pollutants by nanoscale zerovalent iron (nZVI), (3) the ways to improve the performance of nZVI and overcome its limitations and finally (4) the available treatment systems in the literature which is developed based on NZVI to remove ciprofloxacin from aqueous environments.

This work aims to demonstrate the effect of polyethylene sorbitan monolaurate (PSM) on the properties and reactivity of nanoscale zero-valent iron (nZVI). PSM was used in this work to prepare an emulsified nZVI to overcome the particle aggregation phenomenon of nZVI and show the prepared particles with good properties. For that purpose, TEM, XRD and reactivity test of nitrate and phosphorus were performed to show the changes in the performance of nZVI after being emulsified with PSM. The results showed that the emulsified (PSM) greatly improved the removal efficiency of nitrate. Moreover, PSM enhanced the particle dispersion of nZVI and showed the particles with good properties.The results showed that the emulsified nZVI with PSM was also suitable for reduction of nitrate even at a wide range of pH. This study proposed that the emulsified nZVI could have a significant contribution in the aspects of water treatment only for the reducible contaminates.

The aim of the present study is developing a magnetic nanoscale zero-valent iron/zeolite (nZVI/Z) composite towards the efficient removal of ammonia-nitrogen (NH4+-N) from aqueous solutions. Series of batch experiments were conducted to investigate the effect of different factors on the removal efficiency, including pH effect, aerobic/anaerobic, NH4+-N initial concentration, and temperature. The mixing mass ratio of nZVI/Z was optimized to reach the optimal ratio (0.25 g nZVI: 0.75 g zeolite), corresponding to the best removal efficiency of 85.7% after 120 min of reaction. Results revealed that nZVI/Z is efficient for NH4+-N removal from water at a wide pH range (3.0–10.0), with superiority to the neutral conditions. Moreover, aerobic ambient and normal temperature of 25 °C were the optimal conditions for the removal process of NH4+-N. Removal mechanisms involved electrostatic attraction, ion exchange, and adsorption. Generally, nZVI/Z has great potential towards the practical applications of NH4+-N removal from water.

There is a growing interest in deploying nanoscale zero valent iron (NZVI) in permeable reactive barriers (PRBs) for groundwater remediation. In the present study a series of packed-column experiments were conducted in order to investigate the effectiveness of phosphorus removal from groundwater using NZVI and bimetallic NZVI/Cu as reactive materials within PRBs. Seven sets of packed-column experiments were conducted in order to study the effect of different design parameters for PRB; including delivery approach of NZVI into porous media, PRB's configuration, coexisting groundwater ions and change in flowrate. Results implied that doping NZVI surface with copper had an anti-aggregation effect and enhanced its performance in terms of phosphorus removal 2.2 times higher than bare NZVI. Moreover, the lower flowrate (10 ml/min) demonstrated improved phosphorus removal by 22% compared with higher flowrate (60 ml/min). Additionally, groundwater ions barely interfered phosphorus removal process with only ±6%. Overall, geochemical properties and characteristics of the supporting materials were key parameters in the removal process of phosphorus by NZVI/Cu.

Radioactive cesium was resealed to the environment as a result of many nuclear incidents. An effective treatment system is urgently needed to safely handle radioactive cesium-contaminated waters. Based on nanoscale zerovalent iron (nZVI) and zeolite, nine adsorbents were synthesized and applied to remove cesium from aqueous solutions. Magnetic zeolite composite (Ze/Fe0) was selected as the ideal adsorbent for treating cesium contaminated waters in a lab-scale continuous treatment system (LSCTS). The optimization process of the (Ze/Fe0) composite revealed that 1:1 is the optimum mass ratio between zeolite and nZVI. Furthermore, the optimization process proved that the initial pH and temperature have no significant effect on the adsorption of cesium by (Ze/Fe0) composite and the optimum dosage of (Ze/Fe0) composite is 5 g L−1. XRD and SEM results showed that the (Ze/Fe0) composite has an irregular shape with a poor crystalline structure. Kinetic and equilibrium data were best described by pseudo second order and Freundlich isotherm models. Seawater and groundwater experiments illustrated that the removal of cesium by (Ze/Fe0) composite was inhibited due to the existence of competing cations. Eight cycles of LSCTS were performed to examine the performance of (Ze/Fe0) composite in treating continuous streams of cesium contaminated waters. In all cycles except the cycle of treating contaminated seawater, LSCTS succeed to treat continuous flows of 1 mg L−1 cesium contaminated water with 100% overall removal efficiency. For treating contaminated seawater, pre-treatment unit is required to reduce the salinity of the contaminated seawater before staring the treatment process.

This study investigates the efficacy of nano-zero-valent iron (nZVI) permeable reactive barriers (PRBs) as an in situ phosphate removal method. Batch equilibrium experiments were conducted to determine maximum adsorption capacity of nano-iron particles for phosphate to be 54.34 mg-P/g-Fe. Short-term experiment was performed for a period of a month through three sandy soil columns with different configurations of nZVI reactive layers. Initial concentration of 25 (PO4–P) mg/L was introduced to the columns, while effluent samples were collected for analysis. Numerical model was developed to simulate the 1-D advective–dispersive reactive transport of phosphate through the porous media in the three columns. Sensitivity analysis of model parameters was performed, expressed by the change in the effluent concentration with respect to variation in the value of model critical parameters. Optimization of transport process in columns was based on minimizing the sum of squared error values between measured and predicted effluent concentration. Phosphate breakthrough curves implied that Column 2 (C2) with two reactive layers showed a slight better performance in phosphate removal than Column 1 (C1) with maximum efficiency of 98.9% after only 17 h from the beginning of the experiment, whereas phosphate concentration in Column 3 (C3) reached the full saturation by the 9th day. The model verification with experimental data showed a reasonable agreement with a correlation coefficient (R2) ranging from 0.97 to 0.99. The results in this study confirmed that such presented model can be used for the promotion of the preliminary design of PRBs.

The main aim of this study is to investigate the suitability of several adsorption isotherms and kinetic models for describing the removal of phosphorus (P) from aqueous solutions by nanoscale zero-valent iron (NZVI). Removal efficiency was assessed through batch experiments using initial P-concentration ranged from 5 to 100 mg/L. Statistical error analysis was conducted to examine the validity of the applied models to interpret the removal process. Results showed that NZVI dosage of 1 g/L could remove up to 76.8 mg-P with 100 mg/L of P-initial concentration. Moreover, Langmuir isotherm and pseudo 2nd order kinetic model were the best models to describe the experimental data of P-sorption onto NZVI, with the highest linear and non-linear correlation (R2). Results suggested that chemisorption is the main mechanism involved in P-removal by NZVI in addition to the possibility of physical-electrostatic deposition of P-species onto the surface of NZVI within the liquid-solid controlling step. Functional error analysis quantitatively confirmed the applicability of the proposed isotherm and kinetic models in describing the P-sorption data. Akaike Information Criterion (AIC) values confirmed the goodness-of-fit of the Langmuir isotherm model, linear pseudo 2nd and 1st order models, and non-linear pseudo 1st order model to the experimental data. Thermodynamic analysis, with high enthalpy value of 67.87 kJ/mol, confirmed endothermic nature in the NZVI/P system and the involvement of physio/chemisorption process. The present insights into sorption and reaction rate analysis of P by NZVI revealed that it could have subsequently occurred on two main steps of liquid-film and liquid-solid diffusions.

In this study, nanoscale zero valent iron (Fe0) was coated with different layered hydroxide coatings (Mg/Al/Ca(OH)N) to enhance its suspension stability in aqueous solution and transportability within the porous media. Morphological characteristics, crystallinity and surface elemental composition of the synthesized bare (Fe0) and coated (C-Fe0) were investigated using TEM, XRD and SEM-EDS analyses respectively. Suspension stability of Fe0 and C-Fe0 suspensions with different [Mg or Al or Ca/Fe: 0.2–1.0 wt/wt] coating ratios was investigated through several sets of 180 min settlement experiments. Moreover, packed-column experiments were conducted to evaluate the mobility of the prepared materials through porous media. Settlement results were highly consistent with mobility investigation, where C-Fe0 [Mg/Fe]1.0 showed the best performance in both with around 88% relative suspension efficiency and 93% penetration efficiency (5 times higher than Fe0). A reciprocal relation was found between particle size, crystallinity and reactivity of the C-Fe0, where the finest sizes exhibited higher crystallinity and better removal of the two targeted nutrients. Furthermore, the progressive dissolution of the Mg(OH)2 shell compared with the other coating materials resulted in its superior prolonged reactivity. The presented C-Fe0 could be promising towards enhanced performance of the reactive nanoparticles in the real water treatment applications.