Role of MnO2 in controlling iron and arsenic mobilization from illuminated flooded arsenic-enriched soils

Abstract

This study examined the role of intermittent illumination/dark conditions coupled with MnO 2-ammendments to regulate the mobility of As and Fe in flooded arsenic-enriched soils. Addition of MnO 2 particles with intermittent illumination led to a pronounced increase in the reductive-dissolution of Fe(III) and As(V) from flooded soils compared to a corresponding dark treatments. A higher MnO 2 dosage (0.10 vs 0.02 g) demonstrated a greater effect. Over a 49-day incubation, maximum Fe concentrations mobilized from the flooded soils amended with 0.10 and 0.02 g MnO 2 particles were 2.39 and 1.85-fold higher than for non-amended soils under dark conditions. The corresponding maximum amounts of mobilized As were at least 92 % and 65 % higher than for nonamended soils under dark conditions, respectively. Scavenging of excited holes by soil humic/fulvic compounds increased mineral photoelectron production and boosted Fe(III)/As(V) reduction in MnO 2-amended, illuminated soils. Additionally, MnO 2 amendments shifted soil microbial community structure by enriching metal-reducing bacteria (e.g., Anaeromyxobacter, Bacillus and Geobacter) and increasing c-type cytochrome production. This microbial diversity response to MnO 2 amendment facilitated direct contact extracellular electron transfer processes, which further enhanced Fe/As reduction. Subsequently, the mobility of released Fe(II) and As(III) was

Biophotoelectrochemistry for renewable energy and environmental applications

“…The study on the natural BPEC systems at the water-sediment interface is at a very early stage and mainly focuses on the metal elements. It was reported that the photo-excited mineral photoelectrons from various SQDs such as ZnS, MnO 2 and TiO 2 , participated in the microbial electron transfer chain for As/Fe reduction in flooded soils, and the synchronously excited photoholes could be scavenged by humic/fulvic acids (Dong et al, 2021;Chen et al, 2019cChen et al, , 2019d. The introduction of these SQDs would increase the electrical conductivities of soil particles and enhance the production of c-type cytochrome, thereby enabling a long-distance photoelectron transfer.…”

“…The introduction of these SQDs would increase the electrical conductivities of soil particles and enhance the production of c-type cytochrome, thereby enabling a long-distance photoelectron transfer. Accordingly, the abundance of metal-reducing bacteria (e.g., Anaeromyxobacter, Bacillus and Geobacter) would facilitate the metal reduction at the water-sediment interface (Dong et al, 2021). In this paper, we have introduced both BPEC basics and systems and discussed the photoelectron transfer mechanisms via direct and indirect pathways.…”

Inward-to-outward assembly of amine-functionalized carbon dots and polydopamine to Shewanella oneidensis MR-1 for high-efficiency, microbial-photoreduction of Cr(VI)

“…Our previous findings also demonstrated that heterojunctions of specific carbon-based nanomaterials (such as graphene) could up-regulate the expressions of specific c-cyts of EABs . Herein, the total production of c-cyts for SW, ISW and ISW@PDA@NCDs cells was determined using the protocols for the c-cyt ELISA Kit (Shanghai Lanpai Biotechnology, China) (Dong et al, 2021). Briefly, a 10 μL test sample and 40 μL sample diluent were firstly added in a 96-well plate and then mixed using a homogenizer for 3 min.…”

The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System

“…Given that the reductive transformation of any dissolved species by electrons from the metal body is impossible [18,19,29], this study established that adding MnO 2 to Fe 0 /H 2 O systems should be regarded as creating a reactive Fe/Mn mineral mixture. The geochemistry of such mixtures is well-known to geochemists [9,10,30,31]. However, their suitability for decontaminating engineered systems is yet to be systematically investigated [30,31].…”

“…The geochemistry of such mixtures is well-known to geochemists [9,10,30,31]. However, their suitability for decontaminating engineered systems is yet to be systematically investigated [30,31].…”