Self-purification of actual wastewater via microbial-synergy driving of catalyst-surface microelectronic field: A pilot-scale study.

High energy consumption is impedimental for eliminating refractory organics in wastewater by current technologies. Herein, we develop an efficient self-purification process for actual non-biodegradable dyeing wastewater at pilot scale, using N-doped graphene-like (CN) complexed Cu-Al2O3 supported Al2O3 ceramics (HCLL-S8-M) fixed-bed reactor without additional input. About 36% chemical oxygen demand removal was achieved within 20 min empty bed retention time and maintained stability for almost one year. The HCLL-S8-M structure feature and its interface on microbial community structure, functions, and metabolic pathways were analyzed by density-functional theory calculation, X-ray photoelectron spectroscopy, multiomics analysis of metagenome, macrotranscriptome and macroproteome. On the surface of HCLL-S8-M, a strong microelectronic field (MEF) was formed by the electron-rich/poor area due to Cu-π interaction from the complexation between phenolic hydroxy of CN and Cu species, driving the electrons of the adsorbed dye pollutants to the microorganisms through extracellular polymeric substance and the direct transfer of extracellular electrons, causing their degradation into CO2 and intermediates, which was degraded partly via intracellular metabolism. The lower energy feeding for the microbiome produced less adenosine triphosphate, resulting in little sludge throughout reaction. The MEF from electronic polarization is greatly potential to develop low-energy wastewater treatment technology.

Enhanced purification of kitchen-oil wastewater driven synergistically by surface microelectric fields and microorganisms.

The stable structure and toxic effect of refractory organic pollutants in wastewater lead to the problem of high energy consumption in water treatment technology. Herein, we propose a synergistic purification of refractory wastewater driven by microorganisms and surface microelectric fields (SMEF) over a dual-reaction-center (DRC) catalyst HCLL-S8-M prepared by an in situ growth method of carbon nitride on the Cu-Al2O3 surface. Characterization techniques demonstrate the successful construction of SMEF with strong electrostatic force over HCLL-S8-M based on cation-π interactions between metal copper ions and carbon nitride rings. With the catalyst as the core filler, an innovative fixed bed bioreactor is constructed to purify the actual kitchen-oil wastewater. The removal efficiency of the wastewater even with a very low biodegradability (BOD5/COD = 0.33) can reach 60% after passing through this bioreactor. An innovative reaction mechanism is revealed for the first time that under the condition of a small amount of biodegradable organic matter, the SMEF induces the enrichment of electric active microorganisms (Desulfobulbus and Geobacter) in the wastewater, accelerates the interspecies electron transfer of intertrophic metabolism with the biodegradable bacteria through the extracellular electron transfer mechanism such as cytochrome C and self-secreted electron shuttle. The electrons of the refractory organic pollutants adsorbed on the surface of the catalyst are delocalized by the SMEF, which can be directly utilized by microorganisms through EPS conduction. The SMEF generated by electron polarization can maximize the utilization of pollutants and microorganisms in wastewater and further enhance degradation without adding any external energy, which is of great significance to the development of water self-purification technology.

Peroxymonosulfate as inducer driving interfacial electron donation of pollutants over oxygen-rich carbon-nitrogen graphene-like nanosheets for water treatment.

Herein, a novel metal-free catalyst consisting of multiporous oxygen-rich carbon-nitrogen graphene-like nanosheets (OLAA-CN NSs) is first developed through a staged temperature-programmed calcination of l-ascorbic acid (LAA)-modified dicyandiamide precursor. It is found that the oxygen species from l-ascorbic acid (OLAA) are introduced into the graphene-like basic matrix and replace partial N atoms to form the COC-R structure, leading to the non-uniform distribution of electrons on the catalyst surface, and the formation of electron-rich centers around the COC microareas according to a series of characterization techniques. As a result, OLAA-CN NSs exhibits excellent performance for refractory pollutant removal in the presence of peroxymonosulfate (PMS) and dissolved oxygen. Some pollutants with complex structures are even completely degraded within only 1 min. The interface reaction mechanism is further revealed that PMS mainly acts as an active inducer to drive the electron donation of pollutants over OLAA-CN NSs. These electrons are finally utilized by dissolved oxygen to generate reactive oxygen species (ROS) through the interface process. This reaction system results in pollutants that can either be cleaved directly by surface oxidation process or degraded by the attack of the generated ROS, such as singlet oxygen (1O2) and superoxide radicals (O2•-), through oxygen activation, which significantly reduces the resource and energy consumption in advanced wastewater treatment by harnessing the energy of pollutants and dissolved oxygen in the water.

Efficient Fenton-like Process Induced by Fortified Electron-Rich O Microcenter on the Reduction State Cu-Doped CNO Polymer.

The discharge of organic pollutants threatens the environment and health and is also a waste of organic energy. Here, the reduction state Cu (RSC) species-doped carbon-nitrogen-oxygen polymer (RSC-CNOP) is synthesized from high-temperature polymerization of a Cu-polyimide precursor, which is used as a Fenton-like catalyst and exhibits excellent performance for pollutant degradation, accompanied by the utilization of the electron energy of the pollutants. Experiments and theoretical calculations reveal the promotion mechanism. The formed Cu(RSC)-O-C(π) electron-transfer bridges in RSC-CNOP induce the bidirectional electron transfers from RSC to O and from C(π) to O (RSC → O ← π), forming the polarized reaction micro-areas (reinforced electron-rich O microcenters and electron-poor C(π) microcenters). The free electrons in electron-rich centers of RSC-CNOP are as many as ∼8 times that of the pure CNOP sample from the electron paramagnetic resonance measurement. Pollutants are oxidized by supplying electrons to electron-poor microcenters, and H2O2 can be selectively reduced to •OH (also destruct pollutants) in the electron-rich microcenter over RSC-CNOP. This work reveals that the energy and electrons of pollutants can be efficiently utilized in the Fenton-like system through constructing and reinforcing the polarized dual reaction microcenters.

In situ generation and efficient activation of H2O2 for pollutant degradation over CoMoS2 nanosphere-embedded rGO nanosheets and its interfacial reaction mechanism.

Consumption of additional H2O2 is necessary in classical Fenton catalysis. Herein, we report a novel and special nanocatalyst consisting of CoMoS2 nanosphere-embedded, reduced graphene oxide (rGO) nanosheets (CMS-rGO NSs). This nanocatalyst was discovered to have an impressive reactivity for in situ generation and synchronistical activation of H2O2 in different active centers, yielding fast and efficient degradation of the pollutants. The reaction rate is ∼21 times higher than that of conventional Fenton catalysts. The characterization shows that countless flower-like CoMoS2 nanospheres are uniformly embedded in the rGO nanosheets through MoSC bonding bridges in CMS-rGO NSs, which leads to activation of the π electrons and their transfer from rGO to the metal centers (π → M). The formed MoOCo further leads to a distribution of orientations of the electrons around the metal centers due to the different electronegativity of Mo and Co. During the reaction, the dissolved O2 is efficiently reduced to HO2/O2- around the electron-rich Mo center, and HO2/O2- is further reduced to H2O2 around the Co center. The generated H2O2 is finally reduced to OH for degrading dyes in the electron-rich metal (Mo or Co) centers of CMS-rGO NSs. The dye pollutants also act as electron donors, and they are directly degraded in the electron-poor π-center of CMS-rGO NSs, which promote the electron transfer cycle and achieve electron gain-loss balance. This discovery provides a new strategy for H2O2 generation-activation and pollutant degradation through constructing electron transfer bridges over the surface of catalysts.