Kun Wu,Meng Wang,Angzhen Li,Zixuan Zhao,Ting Liu,Xiaodan Hao,Shengjiong Yang,Pengkang Jin
Mn-oxide-containing adsorbents have shown outstanding performances for the removal of As(III) through an “oxidation-adsorption” process. In this study, a new adsorbent of Fe-Mn-Cu ternary oxide (FMCTO) was fabricated to improve the redox reaction rate and to enhance the recovery of oxidative ability. FMCTO exhibited a stronger ability for As(III) removal than most of other adsorbents, because it has better oxidative capability for As(III) oxidation. The state of dynamic equilibrium for As(III) removal by FMCTO could be basically achieved within 3 h, and the As removal efficiency reached 98.9% at time = 24 h. The Langmuir As adsorption capacity of FMCTO was determined to be 204.8 mg/g. The As(III) removal efficiency of FMCTO was further boosted by 7% through oxygen gas aeration and decreased by 19% with nitrogen gas in the ambient during the first 3 h, indicating the positive effect of oxygen on As(III) oxidation. EPR and UV spectra methods were used to confirm the generation of superoxide radical (O 2 − ) and the enhanced production of Mn(III) soluble species on FMCTO surfaces, thus achieving a better As(III) oxidation performance. The XPS analysis results showed that the electron transfer from Cu(I) to Mn(IV) could improve the stability of Mn(III) within FMCTO. Meanwhile, Mn(II) ions could be oxidized to Mn(III) by O 2 − . Hence, the formation of a redox cycle between Mn(II) and Mn(III) along with the production of O 2 − plays a vital role in the upgraded As(III) removal mechanisms. This study provides new insights into the promotion of the capability of Mn-containing adsorbents for achieving the improved removal of As from As(III)-contaminated water.
The solid carbon source (poly-3-hydroxybutyrate-co-3-hyroxyvalerate, PHBV) and manganese oxide mineral (Mn ore) were proposed firstly as co-substrates for eliminating nutrients and sulfamethoxazole (SMX) in this study. Results showed that high-rate nitrate and phosphate removal could be achieved in PHBV/Mn ore systems with the average efficiencies of 90% and 66.7%, respectively, although the addition of SMX decreased denitrification performance by 4.5–10.5%. SMX was removed mainly via biodegradation of enriched denitrifying microbes, with the average removal efficiency of 20–50% in PHBV/Mn ore systems, which was higher than that in PHBV systems. The existence of Mn ore markedly shaped the microbial community structure, leading to the dominant bacteria transforming from Microscillaceae to Sporomusaceae. The genera of Geobacto r, Desulfovibrio and Anaerovorax were found to maintain the stability of microbial system as keystone species. Surprisingly, large amount of Mn(II) was accumulated, which not only verify the involvement of Mn cycling in decontamination process, but also might explain the propagation of ARGs ( tnpA-04 and tnpA-05 ) in host microorganisms. Therefore, the optimized mixture proportion of PHBV and Mn ore should be further estimated avoiding Mn (II) accumulation in the effluent. On the whole, these results might shed light on new insight for advanced treatment of nutrients and emerging pollutants in biofilm reactors.
The release of Mn(II) occurs in the degradation of organic matters by manganese ore (MnO 2 ), resulting in a reduced efficiency. During the degradation of ciprofloxacin (CIP), in a biofilter, this paper put forward a novel method that similar to the geo-cycle of Mn (MnCS) on the Earth to regenerate MnO 2 . The freshly prepared MnO 2 was suitable for the use in the MnCS. It indicated that the mutual conversion between Mn(II), Mn(III), and Mn(IV) in the MnCS, which was driven by CIP and manganese oxidizing bacteria (MnOB), could maintain the activity of MnO 2 . The MnCS showed feasibility in the coexistence of ammonia or humic acid , and provided a kinetic degradation. The physicochemical features of MnO 2 before and after bio-regeneration were characterized by TEM , XRD, BET, and XPS. It was found that the morphological structure of MnO 2 became loose and the maximum peak of pore size distribution became smaller, but the increase of surface area, the change of Mn(III/IV) content, and the decrease of crystallinity favored the bio-regeneration process. Moreover, as a mediator in the MnCS, the group of MnOB was dramatically inhibited by CIP, and the bacterial community had changed significantly. The typical MnOB shared low abundance in the biofilter, while the rarely reported genera (e.g. Sphingomonas ) that related to the formation of Mn deposits appeared to be involved in the MnCS.
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