H*ads dynamics engineering via bimetallic Pd-Cu@MXene catalyst for enhanced electrocatalytic hydrodechlorination.

Electrocatalytic hydrodechlorination (EHDC) is a promising approach to safely remove halogenated emerging contaminants (HECs) pollutants. However, sluggish production dynamics of adsorbed atomic H (H*ads) limit the applicability of this green process. In this study, bimetallic Pd-Cu@MXene catalysts were synthesized to achieve highly efficient removal of HECs. The alloy electrode (Pd-Cu@MX/CC) exhibited better EHDC performance in comparison to Pd@MX/CC electrode, resulting in diclofenac degradation efficiency of 93.3 ± 0.1%. The characterization analysis revealed that the Pd0/PdII ratio decreased by forming bimetallic Pd-Cu alloy. Density functional theory calculations further demonstrated the electronic configuration modulation of the Pd-Cu@MXene catalysts, optimizing binging energies for H* and thereby facilitating H*ads production and tuning the reduction capability of H*ads. Noteably, the amounts and reduction potential of H*ads for Pd-Cu@MXene catalysts were 1.5 times higher and 0.37 eV lower than those observed for the mono Pd electrode. Hence, the introduction of Cu into the Pd catalyst optimized the dynamics of H*ads production, thereby conferring significant advantages to EHDC reactions. This augmentation was underscored by the successful application of the alloy catalysts supported by MXene in EHDC experiments involving other HECs, which represented a new paradigm for EHDC for efficient recalcitrant pollutant removal by H*ads.

Hematite and multi-walled carbon nanotubes stimulate a faster syntrophic pathway during methanogenic beet sugar industrial wastewater degradation.

The quest to understand and subsequently improve the role played by bacteria and archaea in the degradation of organic matter both in natural and engineered anaerobic ecosystems has intensified the utilization of nanoparticles. Microbial communities are known to syntrophically cooperate during the anaerobic conversion of substrates into methane gas via the direct exchange of electrons. In this study, the role of hematite (Fe2O3-750 mg/L) and multi-walled carbon nanotubes (MWCNTs-1500 mg/L) during the degradation of beet sugar industrial wastewater (BSIW) in a batch experiment was investigated. Hematite and MWCNTs enhanced methane gas generation by 35 and 20%, respectively. Furthermore, microbial syntrophic communities might have exchanged metabolic electrons more directly, with hematite and MWCNTs serving as electron conduits between the homoacetogens and methanogens, thereby establishing a direct interspecies electron transfer (DIET) pathway. Additionally, hematite and MWCNTs enriched the bacteria Firmicutes while Chloroflexi reduced in abundance. Scanning electron microscopy and confocal laser scanning microscopy demonstrated that extracellular polymeric substances had noticeable interactions with both hematite and MWCNTs. Our findings provide vital information for more understanding of the response of microbes to hematite and MWCNTs in a complex natural environment.

Performance of CSTR-EGSB-SBR system for treating sulfate-rich cellulosic ethanol wastewater and microbial community analysis.

Performance and microbial community composition were evaluated in a two-phase anaerobic and aerobic system treating sulfate-rich cellulosic ethanol wastewater (CEW). The system was operated at five different chemical oxygen demand (COD)/SO42- ratios (63.8, 26.3, 17.8, 13.7, and 10.7). Stable performance was obtained for total COD removal efficiency (94.5%), sulfate removal (89.3%), and methane production rate (11.5 L/day) at an organic loading rate of 32.4 kg COD/(m3·day). The acidogenic reactor made a positive contribution to net VFAs production (2318.1 mg/L) and sulfate removal (60.9%). Acidogenic bacteria (Megasphaera, Parabacteroides, unclassified Ruminococcaceae spp., and Prevotella) and sulfate-reducing bacteria (Butyrivibrio, Megasphaera) were rich in the acidogenic reactor. In the methanogenic reactor, high diversity of microorganisms corresponded with a COD removal contribution of 83.2%. Moreover, methanogens (Methanosaeta) were predominant, suggesting that these organisms played an important role in the acetotrophic methanogenesis pathway. The dominant aerobic bacteria (Truepera) appeared to have been responsible for the COD removal of the SBR. These results indicate that dividing the sulfate reduction process could effectively minimize sulfide toxicity, which is important for the successful operation of system treating sulfate-rich CEW.

Microbial community structural analysis of an expanded granular sludge bed (EGSB) reactor for beet sugar industrial wastewater (BSIW) treatment.

A looming global energy crisis has directly increased biomethanation processes using anaerobic digestion technology. However, much knowledge on the microbial community structure, their distribution within the digester and related functions remains extremely scanty and unavailable in some cases, yet very valuable in the improvement of the anaerobic bioprocesses. Using pyrosequencing technique based on Miseq PE 3000, microbial community population profiles were determined in an operated mesophilic expanded granular sludge bed (EGSB) reactor treating beet sugar industrial wastewater (BSIW) in the laboratory scale. Further, the distribution of the organisms in the lower, middle and upper sections within the reactor was examined. To our knowledge, this kind of analysis of the microbial community in a reactor treating BSIW is the first of its kind. A total of 44,204 non-chimeric reads with average length beyond 450 bp were yielded. Both bacterial and archaeal communities were identified with archaea predominance (60 %) observed in the middle section. Bayesian classifier yielded 164 families with only 0.73 % sequences which could not be classified to any taxa at family level. The overall phylum predominance in the reactor showed Firmicutes, Euryarchaeota, Chloroflexi, Proteobacteria and Bacteroidetes in the descending order. Our results clearly demonstrate a highly diverse microbial community population of an anaerobic reactor treating BSIW, with distinct distribution levels within the reactor.