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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.

Microbial fuel cells (MFC) are a versatile technology for power generation from biodegradable solid wastes. This study examines the addition of bare and coated Fe0 nanoparticles to the anolyte of a lab-scale MFC for the first time. Four different coating ratios (Mg/Fe:0.1, Mg/Fe:0.2, Mg/Fe:0.5, and Mg/Fe:1.0) were separately added and comparatively evaluated for power generation. The study examined the use of four different waste sludge substrates, different pH, and aerobic enriched cathode chambers' effect on wastewater treatment and current production. Results showed that Mg/Fe:0.2 was promising to increase the voltage by 441 % compared to the control and provide the maximal power density (833.33 mW/m2; 1387.25 µW/g.VS; 3.204 mA). The current generation's stability was achieved under neutral pH, and the power density output is maintained high under anaerobic conditions. The addition of Mg/Fe is an effective method to enhance electricity generation and sludge digestion. However, additional parameters should be considered.

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.

Nanoscale zero-valent iron (nZVI) is regarded as one of the most effective materials for environmental remediation. However, nZVI particles tend to aggregate rapidly due to their magnetic properties which leads to decrease their effectiveness in water treatment. To overcome the aggregation problem of nZVI particles and increase their reactivity, four different polymers were used during the synthesis of nZVI including polyacrylamide (PAA), carboxymethyl cellulose (CMC), Polyethylene sorbitan monolaurate (PSM) and polyvinylpyrrolidone (PVP). These polymers were used with different mass ratios varied between 0.04 and 0.40 %, in order to acquire the optimal mass ratio with nZVI and achieve the highest removal of nitrate and phosphorus. The mechanism of polymers adsorption onto the surface of nZVI was explored by conducting SEM-EDX, XRD, and FTIR analysis. TEM was used to examine the suface morphology of nZVI before and after being stabilized with 4 polymers. Results showed that, the sizes were found to be 9.53, 65.4, 106.4, 106.6 and 108.8 nm, using TEM and ImageJ, corresponding to CMC-nZVI, bare-nZVI, PAA-nZVI, PSM-nZVI and PVP-nZVI, respectively. The efficiency of bare and stabilized nZVI on nitrate reduction was found to be in the following the order: PVP-nZVI 99.5% > PAA-nZV 99% > PSM-nZV 97% > CMC-nZVI 70% > bare-nZVI 55.6%. Whereas, for phosphorus adsorption, PAA-nZV 97% was the most effective type, followed by bare-nZVI 76.3%, PSM-nZVI 75%, PVP-nZVI 73% and CMC-nZVI 71%. Therefore, PAA-nZVI exhibited an excellent performance over the rest for both nitrate and phosphorus removal at a wide range of pH. For this reason, four kinetic models were investigated to describe the reaction rate of nitrate and phosphorus removal by PAA-nZVI.

The present study aims to develop a practical approach for the optimal permeable reactive barrier (PRB) design towards Cr(VI) removal from groundwater. Batch and column experiments were performed to investigate the characteristics of the four proposed reactive materials; nanoscale zero-valent iron (Fe0), bimetallic nanoscale zero-valent iron (Fe0/Cu), activated carbon (AC) and sand/zeolite mixture (S/Z). Kinetic analysis and dynamic modeling of the experimental data were implemented to determine the controlling conditions of the reactive performance of the PRB's materials. The sensitivity index of the design parameters was examined as an indicator of their effect on the reactive responses. Moreover, the Response Surface Methodology (RSM) was considered for optimizing the design variables of the PRB based on the practical factorial analysis. Results revealed that Fe0 and Fe0/Cu showed high performance in Cr(VI) removal, with a slight superiority to Fe0, with final removal efficiency values of 89.7 and 84.1%, respectively. Kinetic analysis depicted that pseudo second order was the best fitting model for Cr(VI) removal in the four materials' cases. ANOVA statistical analysis revealed that quadratic polynomial model was the best model, corresponding to the highest correlation efficiency and adequate precision, to describe the relationships in the four PRB's cases between the selected dependent variables; resident time ( t R ), reactive material mass per sectional area of contaminant plume ( M / A ) and reactive material cost ( C o s t P R B ) towards the independent parameters; barrier thickness ( b ) and permeability ( K r ). Additionally, sensitivity analysis has been conducted which depicted the high sensitivity, in the four PRB's cases, of average pore water velocity within the barrier ( v r ) v r and K r with the highest and the second-highest sensitivity index (SI) values towards t R , respectively. The RSM-optimization revealed that Fe0 is the most feasible reactive material, comparing to the other considered materials, with respect to the optimal conditions regarding the long residency ( t R = 22 days) and low cost ( b = 0.521 m), with around 95.2% desirability of its optimal solution. Overall, the current study represents a significant contribution and a vital step towards an accurate PRB's design based on previously determined optimal conditions.

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.