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Finding a good sorbent for phosphorus (P) recovery from the aquatic environment is critical for preventing eutrophication and providing P resources. The activated iron system (mainly consisted of zero-valent iron (ZVI), Fe 3 O 4 and Fe 2+ ) has been reported to exhibit a favorable performance towards various contaminants in wastewater, but its effect on P recovery has not been studied systematically. In this study, we used Fe 2+ -nitrate pretreatment reaction to prepare the activated iron system and then applied it to P recovery. Results show that more than 99% P was removed from water in 60 min; co-existing anions (NO 3 − , Cl − and SO 4 2− ) and natural organic matter (NOM) had little effect on P removal. The P removal capacity of activated iron system is very high compared with currently reported sorbents. Externally-supplied Fe 2+ plays an important role on P removal in the system. Regeneration study shows that the activated iron system exhibited stable P recovery ability by using 0.1 M NaOH solution. Various methods were applied to characterize the ZVI and iron corrosion, and results conclude that sorption precipitation, and co-precipitation contribute to P removal. This method will be promising and have an application potential in the field for efficient and cost-effective recovery of P with cheap microscale zero valent iron. [ABSTRACT FROM AUTHOR]

This work investigated the degradation of methyl orange by ozone in the presence of ferrous and persulfate ions ( O 3 / Fe 2 + / S 2 O 8 2 − ) in a rotating packed bed. The effects of various operating parameters such as initial pH, rotational speed, gas–liquid ratio, ozone inlet concentration and reaction temperature on the degradation rate of methyl orange were studied with an aim to optimize the operation conditions. Results reveal that the degradation rate increased with an increase in rotational speed, gas–liquid ratio and ozone inlet concentration, and reached a maximum at 25 °C and initial pH 4. Contrast experiments involving ozone and ferrous ions (O 3 /Fe 2+ ) were also carried out, and the results show approximately 10% higher degradation rate and COD removal in the O 3 / Fe 2 + / S 2 O 8 2 − process than in the O 3 /Fe 2+ process. Additionally, the intermediates of the degradation process were analyzed to ascertain the degradation products. [ABSTRACT FROM AUTHOR]

In this study, the removal of ibuprofen (IBP), a pharmaceutical compound, from aqueous media by Money plant ( Epipremnum aureum ) was investigated. The effect of ferrous iron (Fe 2+ ) on enhancing the IBP removal rate was also analyzed. The first-order removal rate constants showed higher values for lower IBP initial concentrations in the range of 0.20–0.28 d −1 for an initial concentration of 125 μg L −1 to 0.03–0.13 d −1 for an initial concentration of 1000 μg L −1 . Introducing ferrous iron to the aqueous media enhanced the first-order removal rate constant up to 6.5 times in a 3 d time period. Along with the removal of IBP from the media, the endogenous concentration of H 2 O 2 also decreased presumably by the production of hydroxyl radical ( OH). Reduction in the endogenous H 2 O 2 concentration was recorded to be 38% and 98% in the absence and presence of Fe 2+ respectively in the first day and the H 2 O 2 level remained considerably low until day 7 which then gradually increased slightly. Simultaneous reduction of IBP and endogenous H 2 O 2 concentration could be due to the reaction of IBP with OH and presumably OH production itself accelerated via Fenton reaction. In addition, presence of sodium bicarbonate (NaHCO 3 ) as OH scavenger in the system showed reduction of first-order removal rate constant from 1.30 d −1 to 0.07 d −1 which could be a possible evidence of biological advanced oxidation process which is believed to play an important role in phytoremediation. [ABSTRACT FROM AUTHOR]

Highlights: [•] The ingredients (Fe2 + and H2O2) for Fenton reaction are naturally present in many open waters. [•] Fenton-driven degradation is likely to affect herbicide behavior and fate in natural waters. [•] Microcosm experiments using three common herbicides were conducted to test the hypothesis. [•] Rapid degradation occurred under Fe2+–H2O2 combinations likely to be encountered in the field. [•] The findings shed some light on an overlooked natural process of environmental significance. [Copyright &y& Elsevier]

In this work, nanopyrite particles (NP) were synthesized by ball mill method and used as a novel source of Fe 2 + in the electro-activation of ozone and peroxydisulfate (PDS) for ofloxacin (OFX) removal. Fourier transform infrared spectroscopy, X-ray powder diffraction, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy analyzes were performed to characterize the as-made NP. Optimal values of operating parameters in NP/PDS and NP/ O 3 processes were obtained. The OFX (10 mg L − 1 ) removal efficiency and molar ratio of OFX: oxidant in NP/PDS and NP/ O 3 processes were 92%, 0.1:11 and 89%, 0.1:9, respectively. Although the synergistic effect was observed in both systems, it was more significant in the NP/PDS. The results of free radical tracing showed that HO • and SO 4 • − had the more contribution in NP/ O 3 and NP/PDS systems for OFX degradation, respectively. In this way, the OFX removal mechanism was the effective release of Fe 2 + from the NP in the electro-activation of O 3 and PDS. Moreover, the effect of electrocoagulation process on OFX removal was negligible. The as-made NP overcame the disadvantages of iron electrode corrosion and iron sludge production in the Fe-based classical electro-activation processes. Overall, the performance of the synthesized NP in the OFX oxidation was very successful in terms of sustainability, Fe 2 + distribution, removal efficiency, energy consumption and PDS or O 3 activation. [Display omitted] • Synthesis and characterization of nanopyrite (NP) as a stable activator of oxidants. • NP improved the ability of O 3 or peroxydisulfate (PDS) in ofloxacin (OFX) oxidation. • The synergistic effect was more observed in the NP/PDS process. • The contribution of electrocoagulation process in OFX removal was negligible. • OFX degradation pathways were proposed. [ABSTRACT FROM AUTHOR]

Electrocatalytic properties of anode and the electrolyte composition are important parameters influence the degradation efficiency for aniline wastewater. Ti/RuO 2 -SnO 2 and Ti/RuO 2 -IrO 2 have been fabricated using thermal decomposition method and experiments in electrolyte containing 0.05 M Na 2 SO 4 , 0.05 M NaCl and 0.05 M Na 2 SO 4 +0.005 M FeSO 4 at different current density were conducted to study the influence on aniline degradation. Linear sweep voltammetry (LSV) showed that Ti/RuO 2 -SnO 2 had higher oxygen evolution potential and degrade aniline through electrochemical transformation and electrochemical combustion while Ti/RuO 2 -IrO 2 degrade aniline mainly through electrochemical transformation. The study showed that Ti/RuO 2 -SnO 2 had higher electrocatalytic activity towards the degradation of aniline than Ti/RuO 2 -IrO 2 anode in 0.05 M Na 2 SO 4 and in 0.05 M NaCl electrolyte. The maximum TOC removal efficiency for Ti/RuO 2 -SnO 2 was 64.2% at 40 mA cm−2 in Na 2 SO 4 electrolyte while the average MCE was 1.6% and the average EC TOC was 1.51 kWh (g TOC)−1. On the contrary, the maximum TOC removal efficiency for Ti/RuO 2 -IrO 2 was 63.1% at 40 mA cm−2 in NaCl electrolyte while the average MCE was 1.6% and the average EC TOC was 1.95 kWh (g TOC)−1. The presence of Fe2+ in Na 2 SO 4 electrolyte would decrease the TOC removal efficiency except at low current density (20 mA cm−2) for Ti/RuO 2 -SnO 2. These results indicated that Ti/RuO 2 -SnO 2 and Ti/RuO 2 -IrO 2 anode were suitable in Na 2 SO 4 and NaCl electrolyte, respectively, while the presence of Fe2+ would inhibit aniline degradation. Image 1 • SnO 2 and IrO 2 are used as dopant to Ti/RuO 2 to study the degradation of aniline. • Ti/RuO 2 -SnO 2 exhibit higher MCE and lower EC TOC in Na 2 SO 4 than Ti/RuO 2 -IrO 2. • Ti/RuO 2 -IrO 2 anode was more suitable to be used as the anode in NaCl electrolyte. • Hydroxyl radicals was crucial for aniline degradation in NaCl solution. [ABSTRACT FROM AUTHOR]

Nitroimidazoles are found in pharmaceuticals and personal care products (PPCPs) and, when discharged into the environment, have adverse effects on human health and survival. Advanced oxidation technologies (AOTs) based on persulfate (PS) can rapidly and efficiently degrade organic pollutants via strong oxidizing radicals under activation conditions. This study investigated the degradation of ronidazole (RNZ) by indirect electrolytic generation of PS and its activator, ferrous ion (Fe2+). An electrochemical system was developed, with a high concentration of PS generated at the anode while the activator Fe2+ was produced at the cathode. It showed that ammonium polyphosphate (APP) could effectively promote the electrolysis of PS. A high current efficiency (88%) at the anode could be obtained after 180 min at a high current density (300 mA cm−2). However, Fe2+ was inhibited at the cathode due to material control. The degradation of RNZ in the Fe2+/PS system generated from the electrochemical system was also explored. Increasing PS concentration and Fe2+/PS ratio were beneficial to the RNZ degradation. In homogeneous reactions, the degradation efficiency of RNZ could be improved by decreasing the Fe2+ addition rate through a peristaltic pump. Five intermediates were also detected and the degradation pathways were proposed. These findings provide a new method and mechanism for rapid and efficient degradation of RNZ. Image 1 • PS and Fe2+ at high concentrations can be synthesized simultaneously by electrolysis. • RNZ can be removed by indirect electrolytic generation of PS and its activator Fe2+. • SO 4. - and OH play an important role in RNZ degradation. • Pathways were proposed for RNZ degradation by Fe2+/PS. [ABSTRACT FROM AUTHOR]

The coprecipitation of arsenic with Fe(III) by lime neutralization is widely used in industrial practices to treat arsenic-containing waste waters generated from mineral processing operations. In this work, coprecipitation was conducted directly at pH 8 to simulate the operations in hydrometallurgical practices, which differed from the conventional laboratory operations. Moreover, although ferric is the major species of iron in arsenic-containing waste waters, the coexistence of ferrous ions cannot be ignored. Therefore, the effect of different neutralization modes, as well as the effect of ferrous ions on the removal of arsenic and the stability of the generated arsenic-bearing wastes, was systematically investigated. The result showed that arsenic was still released back into the liquid phase under alkaline conditions even for the samples formed directly at alkaline pH. It was found that the extra addition of Fe(II) may exert negative effect on the stability of the as-formed Fe(II)–Fe(III)–As(V) coprecipitates at pH 7 − 10. The concentration of ferrous ions in the liquid/solid phase decreased with increasing pH for each sample formed at different Fe(II)/Fe(tot). The results indicated that complete oxidation of the ferrous ions before coprecipitation with arsenic should be conducted to achieve optimal stability of the arsenic-bearing wastes for hydrometallurgical practice and waste disposal. • A yukonite-like phase formed which may exert some effects on the behavior of As. • As-bearing solid formed by conventional neutralization method has high stability. • Aqueous Fe(III) concentration increased if more Fe(II) presented in liquid phase. • Fe(II) exerted negative effect on the stability of Fe(III)–As(V) solids at pH ≥ 7. [ABSTRACT FROM AUTHOR]