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Coexistence of organic compounds and heavy metals in aquaculture waters is a widespread problem. In this study, a rapid reduction of Cr(VI) and oxidation of ciprofloxacin (CIP) in a simultaneous manner was firstly reported through the photocatalysis of TiO 2 /Fe 0 composite under aerobic conditions. The significantly enhanced removals of Cr(VI) and CIP by TiO 2 /Fe 0 composite due to a synergetic effect between oxidation and reduction processes. Within 60 min UV light irradiation, the simultaneous removals of Cr(VI) and CIP by TiO 2 /Fe 0 composite were 97.7 and 94.6%, respectively, whereas the corresponding values by TiO 2 were 57.9 and 68.7%. CIP oxidation process could be significantly accelerated under acidic and aerobic conditions. Intriguingly, a low Pb(II) concentration could induce an enhancement of CIP oxidation, whereas a negative effect on both Cr(VI) reduction and CIP oxidation was observed at a relatively high concentration. A low concentration of ethylene diamine tetra-acetic acid (EDTA) did positively affect both Cr(VI) reduction and CIP oxidation processes, whereas a negative effect on CIP oxidation was found at a relatively high concentration. A possible reaction pathway and mechanism between CIP oxidation and Cr(VI) reduction was proposed. CIP was attacked by HO produced from the decomposition of water and photo-excited holes through substitution and hydroxylation processes, leading to the production of a series of intermediates, whereas the Cr(VI) was converted into Cr(III) through the capture of photo-excited electrons and Fe 0 reduction. [ABSTRACT FROM AUTHOR]

In this study, bentonite-supported nanoscale zero-valent iron (B-nZVI) was used as a catalyst to activate persulfate (PS) for the simultaneous removal of Cr(VI) and phenol from aqueous solutions. Experimental results indicated that the presence of bentonite could decrease the aggregation of nZVI and increase its reactivity. The removal rates of Cr(VI) and phenol by B-nZVI system were 99.90% and 6.50%, respectively. Whereas the corresponding values by B-nZVI/PS system were 99.30% and 71.50%, respectively. The presence of persulfate could not significantly decline B-nZVI reactivity toward Cr(VI) reduction but remarkably promote phenol oxidation. The addition of Cr(VI) did positively affect the oxidation rate of phenol, a significant synergistic effect between Cr(VI) reduction and phenol oxidation was achieved in B-nZVI/PS system. A positive correlation between persulfate decomposition and dissolved Fe 2+ was found. Cr(III) species such as Cr 2 O 3 , Cr(OH) 3 were identified in Cr(VI) reduction process, whereas the oxidation products such as catechol, 1,4-benzoquinone, propionic acid and formic acid were identified in phenol oxidation process. The reusability experiments of B-nZVI demonstrated that the structure of B-nZVI was relatively stable after four cycles of reuse. This is the first report for the feasibility of B-nZVI as a catalyst to activate persulfate for the simultaneous removal of heavy metal and organic pollutant. [ABSTRACT FROM AUTHOR]

The applicability of bentonite-supported nanoscale zero-valent iron (B-nZVI) as a catalyst to activate persulfate (PS) for the simultaneous removal of Cr(VI) and phenol was systematically investigated in this study. Experimental results demonstrated that phenol degradation was significantly enhanced under acidic condition and with oxygen supply, whereas the Cr(VI) reduction was not obviously declined. The removal efficiencies of Cr(VI) and phenol in B-nZVI/PS combined system were 99.8 and 72.3%, respectively. Cr(VI) reduction and phenol oxidation was simultaneously achieved in B-nZVI/PS combined system, which provided a promising environmental treatment for industrial wastewater containing metal ions and organic compounds. An acidic condition was more favorable to the decomposition of persulfate for the production of sulfate radicals. Radical scavenging tests revealed that the predominant reactive oxygen species for phenol degradation was SO 4 − , neither HO nor O 2 − . A reaction mechanism, which involves the Cr(VI) removal mainly by the reduction of nZVI and the degradation of phenol mainly by the SO 4 − from the decomposition of persulfate, was proposed. These findings revealed that B-nZVI/PS combined system has a potential in the environmental remediation polluted jointly by organic compounds and/or heavy metals. [ABSTRACT FROM AUTHOR]

Coexistence of organic compounds and heavy metals in industrial wastewater effluent is a serious environmental problem. In this study, pyrite was successfully employed as a photocatalyst for the simultaneous removal of malachite green (MG) and Cr(VI). The removal efficiency of MG and Cr(VI) were 96.7% and 53.1%, respectively after 120 min. The presence of Cr(VI) significantly promoted MG degradation, and the reduction ratio of Cr(VI) was significantly accelerated in the presence of MG, demonstrating an obvious synergism between MG degradation and Cr(VI) reduction. The presence of Cr(VI) did not change the kinetic order of MG degradation. The presence of dissolved oxygen could enhance the degradation ratio of MG, but decrease the reduction ratio of Cr(VI) despite the fact that both Cr(VI) and O 2 are competitive electron acceptors. Photocatalytic efficiency of the coexistence system was superior to that of the single system when the catalyst was continuously used for 5 times. A synergistic mechanism involving reactive oxygen species produced from photo-Fenton-like process for the MG degradation, whereas the Cr(VI) reduction mainly by direct electrons of pyrite, not reaction of O 2 − with Cr(VI) was proposed. This is the first report on the application of pyrite particles as a photocatalyst for the simultaneous removal of organic compounds and heavy metals. [ABSTRACT FROM AUTHOR]

Nowadays, a great increasing attention has been paid to the coexistence of multiple inorganic pollutants in the environment. In this study, a novel crayfish shell biochar-Fe composite (FXB) was successfully produced and effectively used for the synchronous removal of Cr(VI) and phosphates (P) from aqueous solution. Experimental results revealed that FXB exhibited a high performance on the removal of Cr(VI) and P over a broader pH range. The escalating ionic strength and anions like Cl- and NO 3 - showed varying degrees of inhibition effects on Cr(VI) and P removal. The kinetic model of both Cr(VI) and P adsorption fit better with the pseudo-second-order model compared with the pseudo-first-order model. The isotherm of Cr(VI) fit well with the Langmuir model, whereas that of P adsorption fit well with the Freundlich model. Elovich model suggests that both Cr(VI) and P adsorption were the heterogeneous and multi-mechanism processes, and the intra-particle diffusion model confirms that these adsorption processes were dominated by surface and intra-particle diffusion reactions. Both Cr(VI) and P adsorption onto FXB were the spontaneous and endothermic nature. The synchronous removal of Cr(VI) and P could be efficiently achieved using this FXB composite under the certain conditions. A possible reaction mechanism for the synchronous adsorption of Cr(VI) and P onto FXB involving the synergistic effects of surface adsorption, precipitation, reduction and complexation processes was proposed. [Display omitted] • A novel crayfish shell biochar-Fe composite (FXB) was successfully obtained. • FXB exhibited the high Cr(VI) and P adsorption capacities at wide pH values. • Both Cr(VI) and P adsorption onto FXB were the spontaneous and endothermic nature. • The synchronous removal of Cr(VI) and P could be efficiently achieved with FXB. • The mechanism for the synchronous adsorption of Cr(VI) and P was proposed. [ABSTRACT FROM AUTHOR]

Nowadays, nanoscale zero valent iron (nZVI) has been extensively applied for the decontamination of various pollutants, but passivation of nZVI severely affects its reactivity in use. In this study, ultrasound (US)-assisted catalytic reduction of Cr(VI) by an acid mine drainage based nZVI (AMD-nZVI) coupling with FeS 2 system was systematically examined. Results show that the presence of FeS 2 and US induced a synergistic enhancement of Cr(VI) removal by AMD-nZVI. Nearly 98% of Cr(VI) removal was achieved by AMD-nZVI/FeS 2 /US process within 60 min under optimal reaction conditions. Several coexisting substances with lower concentration including Pb(II), Ni(II), bisphenol A (BPA) and 2,4-diclorophenol (2,4-DCP) could be effectively removed in simultaneous manner with Cr(VI) removal. The inhibitory order of water matrix species on Cr(VI) removal was NO 3 − > PO 4 3− > HCO 3 − > Ca2+ > Mg2+ > Cl−, and a serious suppression effect was induced by humic acid (HA). Addition of ethylene diamine tetra-acetic acid (EDTA) and citric acid (CA) could enhance Cr(VI) removal rate. An enhanced reaction mechanism was proposed, which involved the regeneration of more Fe2+ and H+ by AMD-nZVI/FeS 2 /US process, leading to the reduction of Cr(VI) by AMD-nZVI and FeS 2 into Cr(III) species inculding Cr 2 O 3 and Cr(OH) 3. This study well demonstrates that AMD-nZVI/FeS 2 /US process is considered as a potential candidate for the remediation of Cr(VI) in real wasterwater. Image 1 • FeS 2 induced an enhanced removal of Cr(VI) by AMD-nZVI/US process. • The formation of Fe2+ and acidic condition played a primary role in this process. • Removal of Pb(II), Ni(II), 2,4-DCP and BPA could be achieved with Cr(VI) removal. • Most of Cr(VI) species was sucessfully reduced into Cr 2 O 3 and Cr(OH) 3. • Enhanced mechanism of Cr(VI) removal by AMD-nZVI/FeS 2 /US process was proposed. [ABSTRACT FROM AUTHOR]

• A high performance of Cr(VI) removal was obtained in AMD-nZVI/PDS process. • Transformation products of Cr(VI), Cd(II) and ATZ were identified. • SO 4 − contributed to nearly 84% of the overall ATZ degradation. • The possible pathways of ATZ degradation were proposed. • A reaction mechanism for the removals of Cr(VI), Cd(II) and ATZ was proposed. Nowadays, inorganic and organic pollutants always coexist in the environment, thus an economic and efficient treatment is urgently required. In this paper, a novel nanoscale zero valent iron (AMD-nZVI) produced from the reaction of acid mine drainage (AMD) with NaBH 4 was combined with peroxydisulfate (PDS) for the simultaneous removals of Cr(VI), Cd(II) and atrazine (ATZ) in water. Results demonstrate that the reactivity of AMD-nZVI/PDS process toward Cr(VI) removal was superior to that of AMD-nZVI/HCl or AMD-nZVI/H 2 O 2 process. The coexisting species inculding PO 4 3-, HCO 3 −, NO 3 and humic acid exhibited obvious suppression on the Cr(VI) removal. The simultaneous removal efficiencies of Cr(VI), Cd(II) and ATZ by AMD-nZVI/PDS process were high up to 90% within 40 min. Most of Cr(VI) species were converted to Cr 2 O 3 and Cr(OH) 3 , whereas both Cd(OH) 2 and CdO were main Cd(II) species. The radical quenching tests affirmed that SO 4 − was the primary radical species for ATZ degradation. A total of five intermediate products of ATZ were sucessfully identified, and the degradation of ATZ was achieved through dealkylation, dechlorinatione and hydroxylation processes. A possible reaction mechanism involving in Cr(VI) reduction, Cd(II) precipitation and ATZ Fenton-like oxidation by AMD-nZVI/PDS process therefore was proposed. [ABSTRACT FROM AUTHOR]

The pollution of heavy metals and organic compounds has received increased attention in recent years. In the current study, a novel biochar-based iron oxide composite (FeYBC) was successfully synthesized using pomelo peel and ferric chloride solution through one-step process at moderate temperature. Results clearly demonstrate that FeYBC exhibited more efficient removal of Cr(VI) and/or phenol compared with the pristine biochar, and the maximum adsorption amounts of Cr(VI) and phenol by FeYBC could reach 24.37 and 39.32 mg g−1, respectively. A series of characterization data suggests that several iron oxides such as Fe 2 O 3 , Fe0, FeOOH and Fe 3 O 4 were formed on the FeYBC surface as well as oxygen-containing groups. Thermodynamics study indicates that Cr(VI) and phenol adsorption by FeYBC were endothermic and exothermic processes, respectively. Langmuir adsorption isotherm and pseudo-second order models could better explain the Cr(VI) and phenol adsorption behaviors over FeYBC. The Cr(VI) adsorption might be primarily achieved through the ion exchange and surface complexation and reduction, whereas the π–π interaction and electron donor–acceptor complex mainly contributed to phenol adsorption. The findings indicate that the biochar-based iron oxide composites material was an efficient adsorbent for the remediation of industrial effluents containing Cr(VI) and phenol. [Display omitted] • A novel biochar-based iron oxide composite (FeYBC) was firstly synthesized. • FeYBC exhibited more efficient Cr(VI) and phenol removal than pristine biochar. • Langmuir and pseudo second order models well explain Cr(VI) and phenol adsorption. • Cr(VI) and phenol adsorption were endothermic and exothermic nature, respectively. • The possible removal mechanism of both Cr(VI) and phenol adsorption was proposed. [ABSTRACT FROM AUTHOR]