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This study makes a comparison between the pyrite/H 2 O 2 and pyrite/persulfate (PS) Fenton systems to investigate the degradation of Rhodamine B (RhB). The most relevant findings revealed that a significantly negative effect of carbonate and a narrow pH range of 2–4 were found in the pyrite/H 2 O 2 system, whereas a relatively less negative effect of carbonate and a broad pH range of 2–11 were observed in the pyrite/PS system. It was demonstrated that the pyrite catalyst in the pyrite/PS system exhibited better structural stability and showed a relatively limited loss in performance upon reuse as compared to pyrite in the pyrite/H 2 O 2 system. Experiments with different scavengers indicated that HO radicals were the major reactive species responsible for RhB degradation by pyrite/H 2 O 2 . In this case the contribution of radical was in the order of HOHO >O 2 − , whereas the SO 4 − radicals prevailed over HO in the pyrite/PS system. The role of O 2 − in the recycling of Fe(III) to Fe(II) was very important. The possible mechanism for RhB degradation by pyrite/H 2 O 2 mainly involves the reaction of the dissolved Fe 2+ released by the surface of the pyrite with added H 2 O 2 , whereas the reaction of the dissolved Fe 2+ formed in the pyrite with PS triggers degradation in the pyrite/PS system. The degradation of RhB is initiated in both cases by N-de-ethylation, chromophore cleavage and ring opening processes, which leads to the production of a series of oxidation products with smaller molecular sizes. The pyrite/PS system is here proven to be a superior heterogeneous Fenton-like oxidant process for the removal of dyes from wastewater. [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]

[Display omitted] • Persulfate (PS) significantly enhanced AMX removal by TiO 2 @nZVI/UV process. • The decomposition rate of PS in TiO 2 @nZVI/PS/UV process was the highest. • Both HO• and SO 4 •− were the dominant radicals in TiO 2 @nZVI/PS/UV process. • AMX was effectively degraded through hydroxylation and deamination reactions. • A mechanism for the simultaneous removals of AMX and NOF was proposed. In recent years, a serious threat of antibiotic residues in aquatic environments to human health and ecological security has become increasingly widespread attention. In this study, this is the first report on an alternative strategy on enhanced degradation of amoxicillin (AMX) and norfloxacin (NOF) by TiO 2 @nZVI/persulfate (PS) process under UV irradiation. Results revealed that a signficantly synergistic effect on AMX degradation had been achieved in TiO 2 @nZVI/PS/UV process due to the photocatalysis and Fenton-like reactions. NO 3 –, HCO 3 –, PO 4 3- and humic acid exhibited inhibitory effects on AMX degradation, whereas Cl- was negligible on that. The degradation of AMX decreased as the addition of Cr(VI) concentrations increased, whereas the correspond values were enhanced when a low Cu(II) concentration was introduced. TiO 2 @nZVI/PS/UV process was the most efficient for activating PS decomposition. HO•, SO 4 •− and 1O 2 were all generated in TiO 2 @nZVI/PS/UV process, but HO• and SO 4 •− were the dominant radical species for AMX degradation. The AMX intermediates products identified by LC-MS system confirmed AMX was effectively degraded through hydroxylation and deamination reactions. A better performance on the simultaneous removals of AMX and NOF by TiO 2 @nZVI/PS/UV process could be achieved at lower concentration conditions, and the simultaneous reaction mechanism was thereby proposed base on expriment results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxalic acid (OA) maintain a high dissolved Fe2+ in the PC-ZVI/PMS process. • Peroxymonosulfate (PMS) greatly improve atrazine (AE) removal. • The contribution order of reactive species followed as HO• > SO 4 •- greater than1O 2 > O 2 •−. • The possible degradation pathways of AE by PC-ZVI/PMS/OA process proposed. • Enhanced mechanism of Cr6+ and AE removal by PC-ZVI/PMS/OA process was proposed. Nowadays, clean-up of heavy metals and pesticides from environment has received great attention. A green biochar iron composite (PC-ZVI) was successfully synthesized using pomelo peel residues and FeCl 3 solution. Peroxymonosulfate (PMS) was introduced into the PC-ZVI system for Cr(VI) and atrazine (AE) removal, and results showed that PMS greatly promoted Cr(VI) and AE removal. The presence of oxalic acid (OA) could maintain a relatively high dissolved Fe2+ species for Cr(VI) reduction and AE oxidation in the PC-ZVI/PMS process. The contribution order of reactive oxygen species followed as HO• > SO 4 •- greater than1O 2 > O 2 •− in both Cr(VI) and AE removal by PC-ZVI/PMS/OA process. A total of six intermediates products of AE degradation were detected, and AE molecular was effectively degraded into CO 2 , H 2 O, inorganic N and Cl through hydroxylation, substitution and de-alkylation processes. The underlying mechanism of Cr(VI) and AE removal by PC-ZVI/PMS/OA process was also proposed. Most Cr(VI) species were transformed into Cr 2 O 3 and Cr(OH) 3 through reduction and precipitation processes. PC-ZVI has a relatively high recyclability toward both Cr(VI) and AE removal from solutions. The potential toxicity of PC-ZVI solution was small at three PC-ZVI dosages levels, and the corresponding toxicity of AE reaction solution by PC-ZVI/PMS/OA process decreased as reaction time increased. The order of both Cr(VI) and AE removal in different water systems was tap water > river water > lake water > wastewater, and this PC-ZVI/PMS/OA process exhibited the better adaptability in application for several actual water environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new biochar-based magnesium oxide composite (MTBC) was firstly prepared. • TDF adsorption was well described by pseudo-second-order and Langmuir models. • Chemical adsorption process was dominant in TDF adsorption over MTBC. • Simultaneous removals of TDF and DIN has been achieved by MTBC. • A reaction mechanism of TDF and DIN adsorption by MTBC was proposed. In recent years, the ecological security has been seriously threatened by the residues of pesticides in the environment. In this study, a new biochar-based magnesium oxide composite (MTBC) was successfully prepared using Traditional Chinese Medicine residues and MgCl 2 solution, and then applied for the removal of triadimefon (TDF) and/or dinotefuran (DIN) in water. Batch experiments results indicated that 86.42 and 87.86 % of TDF and DIN removals could be obtained by MTBC within 120 min, respectively. The TDF adsorption process was proved to be well fitted with the pseudo-second-order kinetic, Elovich, liquid film diffusion, Intra-particle diffusion and Langmuir isothermal models. The TDF adsorption by MTBC was a spontaneous endothermic reaction, and chemical adsorption process was dominant. The inhibitory of the coexisting anions on TDF removal followed the order of SO 4 2−＜Cl−＜HPO 4 3−＜HCO 3 –. Both TDF and DIN could be simultaneously removed by MTBC at the certain concentrations levels. The possible removal mechanism for the adsorption of TDF and DIN by MTBC was proposed, both TDF and DIN were rapidly distributed and adsorbed on MTBC surface, then diffused into the interior pores structure and were finally adsorbed on MTBC through various reaction processes. The TDF removal process might be involved with hydrogen bonding, π-π interaction, pore filling and electrostatic interaction, while DIN removal might be involved with hydrogen bonding, pore filling and electrostatic interaction. These findings suggested that biochar-based magnesium oxide composite was an effective adsorbent for the remediation of agricultural effluents containing TDF and DIN. [ABSTRACT FROM AUTHOR]