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Antibiotics are pharmaceutical emerging contaminants (ECs) that contaminate the environment and jeopardize public health. More dangerously, the widespread consumption of antibiotics and their impact on water contamination foster the formation and evolution of antibiotic-resistant genes in microbes. Graphene Oxide (GO) is an emerging carbon material with a great potential to operate as an adsorbent to remove antibiotics from water due to its unique physical and chemical properties. Thus, this study briefly reviews topics related to antibiotic removal from water using GO-based materials. This research also summarizes the benefits of GO structural properties, adsorption mechanisms, and the affinity of the GO synthesis method to the quality of the GO produced.

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.

Introduction: In this work, bimetallic nickel/iron nanoparticles (Ni/Fe0) were prepared to enhance rhenium (Re(VII)) immobilization from aqueous solutions, as the surrogate of technetium (Tc(VII)).Methods: Two synthesis approaches of Ni/Fe0, pre-, and post-nucleation, were investigated towards Re(VII) removal. Different characterization techniques were considered to elucidate the physicochemical features of the fresh and reacted materials, such as scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX), X-ray diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES). The influence of several reaction parameters on Re(VII) removal was investigated, including Ni/Fe0 ratio, dosage, initial pH, temperature, and initial concentration.Results and discussion: Results showed a promising potential of Ni/Fe0, either pre- or post-nucleation synthesized, in Re(VII) removal, especially at the early stage of the reaction, where Ni/Fe0: 0.4 yielded almost full removal efficiency of initial 15.0 μM-Re(VII) within the first 10 min of reaction. Even at low Ni/Fe0 dosages, such as 0.25 and 0.5 g/L, reasonable removal efficiency was achieved after 2 h reaction time of ∼73% and ∼98%, respectively. Unlike acidic/neutral pH, alkaline conditions were not favorable for Re(VII) removal by Ni/Fe0 owing to the delayed aqueous corrosion of Fe0-core resulting in insufficiency of electrons available for Re(VII) reduction. The reductive abilities were confirmed by XANES, revealing Re(VII) reduction to Re(IV)/(III) by the released electrons from Fe0-core in both Fe0 and Ni/Fe0 materials. Pseudo-first- and second-order kinetic models were suitable to describe Re(VII) removal by Ni/Fe0, implying physical and/or chemical processes were involved. Zeta potential measurements depicted the point of zero charge (pHPZC) of Fe0 and Ni/Fe0 to be 8.24 and 7.63, respectively, suggesting the involvement of electrostatic sorption of ReO4− on the positively charged surface of Ni/Fe0. The occurrence of multi- and mono-layer sorption within Re(VII) removal process was implicated, following Freundlich and Sips isotherm models. The presence of Ni0/NiO on Fe0-surface resulted in providing an efficient electron-transfer medium that facilitated Re(VII) reduction, leading to impressive kinetic rates. Overall, our study provided valuable insights into the use of Ni/Fe0 for Re(VII) removal from water and offered guidance for future research in such an aspect towards the pilot-scale applications of Tc(VII) removal from nuclear wastewater.

Microbial fuel cells (MFCs) are a versatile technology for power generation from biodegradable solid wastes. This study aimed to investigate Fe(II) and Fe(III) effects on MFC’s power generation and wastewater treatment performance. All MFCs were operated in a batch mode and incubated at a constant temperature (40 ℃) for 45 days of operation. The experimental procedure went through MFCs construction, collection and characterization of waste sludge samples, and bacterial growth counting. Results showed that the Fe(III) addition exhibited a higher power output by 295 % and a shorter start-up time. The microbial growth increased by 92.18 %, and the anolyte’s resistivity decreased with an increase in the organic matter digestion by 52.78 %. However, the amount of power generated in these MFCs was limited by the biological Fe(III) reduction rate high enough to restrict the produced current.

Graphene oxide (GO) has drawn broad recognition as a novel adsorbent for various contaminants due to the unique physicochemical characteristics shown. This research investigated the effect of several graphene oxide synthesis methods on Ciprofloxacin (CIP), Diclofenac (DCF), and Tetracycline (TC) removal in water and optimized the methods experimentally. Material characterizations such as transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) were employed to investigate the surface morphology of GO. A batch test has been done to study the adsorption kinetics. GO synthesis techniques are crucial and have varying impacts on pharmaceutical contaminants removal. The optimized GO synthesis method showed the most reliable CIP removal performance, where 64% of CIP was effectively adsorbed within 10 minutes. The production of high-quality GO for CIP and DCF removal does not rely on sodium nitrate (NaNO3) or phosphoric acid (H3PO4) catalysts. The GO produced without catalysts eliminated 94.3% of DCF within 10 minutes.

Arsenic poisoning has been a great concern for the last two decades because of its extensive problems. Coagulation, ion exchange, ultrafiltration, and adsorption systems have been used for the removal of arsenic from polluted water. In this study, the biosorption process was used owing to eco-friendly, simplicity, biodegradable, and cost effectiveness. The uptake of arsenic from contaminated water by Ulva lactuca, Spirulina platensis, Chlorella vulgaris, orange peel, NZVI, zeolite, and composite of NZVI and algae was studied. This study observed that Chlorella vulgaris and iron coated Chlorella vulgaris absorb arsenic more effectively than other algae and iron coated algae. After 24 hours, Chlorella vulgaris and Fe-coated Chlorella vulgaris absorbs 23% and 67% arsenic from contaminated water, respectively. The presented findings depicted the great potential of using bio-sorbents and the Fe-algae bio-composite for the removal of arsenic from contaminated aqueous solutions.

The development of antimicrobial resistance genes (AMRs) in water was globally accelerated due to the occurrence of ciprofloxacin (CIP) in water. This study aims to precipitate iron nanoparticles (Fe0) on the surface of titanium nanowires (TNWs) through a chemical process to overcome the limitations of Fe0 and efficiently remove CIP from water. TEM and XRD results confirmed the successful synthesis of Fe0 and TNWs. They also proved the successful deposition and dispersion of Fe0 on TNWs. Several (Fe0/TNW) nanocomposites were synthesised with different percentages of TNWs (5, 10, 20, 30, and 50%) to define the best TNWs ratio that will decrease the aggregation of Fe0 nanoparticles and achieve an outstanding removal efficiency of CIP. (Fe0/TNW) nanocomposite with 20% of TNW was nominated as the best nanocomposite because it demonstrated a promising performance, compared with other nanocomposites, by removing more than 67% of CIP with insignificant desorption behaviour during the treatment period (120 min). Dosage of (20%-Fe0/TNW), initial pH of CIP solution and reaction temperature were optimized through a group of batch experiments to efficiently remove CIP from water. The optimum removal of CIP was obtained by 1 g L−1 of (20%-Fe0/TNW) nanocomposite at initial pH of 7 under 35 °C.

Hexavalent chromium is one of the highly toxic heavy metals which could lead to severe health issues when it is discharged into aquifers as industrial wastewater. In the current study nFe0/Cu was successfully employed in PRB technology for Cr(VI) removal from groundwater. Batch and column experiments confirmed the high reactive performance of nFe0/Cu towards Cr(VI) removal by around 85% removal efficiency. The main pathways for Cr-species removal by nFe0/Cu were determined as the reduction of Cr(VI) to Cr(III) by both nFe0 and Cu0 and the precipitation/co-precipitation of Cr(III) with the released iron oxides on the nFe0/Cu surface. The developed 3D-surface response optimization model confirmed the reciprocal relation between the residence time, barrier thickness and hydraulic conductivity. The interaction and sensitivity analysis between the model’s parameters were significantly crucial for defining the optimal design conditions of the nFe0/Cu-PRB. Generally, the current study could represent a great contribution in scaling-up the PRB technology towards the real field applications.

In this study, mini review is introduced on the features of the red microalgae (RMA) and its biotechnological potential in different applications. Since it has unique extremophilic features, Galdieria Sulphuraria (GS) is considered to be a perfect microorganism candidate for various biotechnological applications in water treatment systems. Special interest has been oriented towards the applications of GS in water treatment systems, such as nutrients, biological oxygen demand (BOD) and heavy metals (HMs) removal from wastewater. Also, different future prospects have been suggested in terms of the new and innovative applications of GS in water treatment based on the gaps in the literature, including phycoremediation of HMs, bio-resin production, bio-substrate for nanoparticles, and pharmaceuticals removal from wastewater. Finally, the challenges and limitations of employing GS in biotechnological applications have been reviewed, which revealed that using GS has a great potential in largescale outdoor cultivation without becoming contaminated with other microorganisms.

In this study, a lab-scale microbial fuel cell (MFC) was constructed and power generation output was investigated for 45 days of operation. Nanoscale zerovalent iron (NZVI) and Iron/copper nanoparticles (Cu/NZVI) were added to the anode chamber of the MFC with a concentration of 10 mg/L and their effects were investigated on the MFC performance. Results showed that the maximal power output density values increased by 43.33 % using copper/iron nanoparticles compared to the control MFC. Anode chamber was examined, and results proved that conductivity increased by 13.68% and 23.62% using NZVI and Cu/NZVI, respectively. The chemical oxygen demand COD was tested, and the removal efficiency reached 38.88%, 38.26%, and 52.40% for control, NZVI, and Cu/NZVI MFCs, respectively after 45 days of operation. This study highlights the effect of nanoparticles technology on power generation from activated sludge using microbial fuel cells (MFCs).

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.

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.

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.

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.

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.