Non-woven cotton fabric based intimately coupling of photocatalysis and biodegradation system for efficient removal of Cu(II) complex in water

Combined addition of γ-PGA and DCD facilitates phytoremediation of heavy metals and carbon sequestration: A field experiment

A field study examined the impact of γ-polyglutamic acid (γ-PGA), both alone and in combination with dicyandiamide (DCD), on the phytoremediation of soil contaminated with Cd, Pb, and Zn. This study focused on the heavy metal (HM) accumulation, and soil CO2 and N2O emissions in Cosmos sulphureus and Pennisetum americanum × P. purpureum, and soil microbial communities. The findings indicated that the application of γ-PGA, either alone or in combination with DCD, increased plant yield and HM bioavailability in the soil, leading to improved HM uptake by plants. For P. americanum × P. purpureum, compared to CK treatment, the combined addition of γ-PGA and DCD increased the Cd, Pb, and Zn extraction by 131.4%, 80.6%, and 99.7%, respectively. Compared to γ-PGA alone, the combined addition of γ-PGA and DCD reduced the soil N2O emission and global warming potential by 26.4% and 39.1%, respectively. P. americanum × P. purpureum treated with γ-PGA and DCD achieved C sequestration of 829 kg ha-1. Moreover, the application of γ-PGA, alone or in combination with DCD, increased the abundance of soil microbes. Bacteria (Proteobacteria, Actinobacteriota, and Firmicutes) as well as fungi (Basidiomycota and Mortierellomycota) contributed to HM accumulation and resistance to stress by altering soil enzyme activities, C and N fractions. Additionally, Acidobacteriota and Patescibacteria are beneficial to reducing soil GHG emissions and GWP in P. americanum × P. purpureum soil treated with γ-PGA and DCD. In conclusion, P. americanum × P. purpureum with the combined addition of γ-PGA and DCD increased HM extraction and total C sequestration in the plant-soil system. This approach offers a scientific basis and promising approach for integrating phytoremediation with C sequestration.

Decomposition of metal-organic complexes and metal recovery in wastewater: A systematic review and meta-synthesis

Metals are rarely found as free ions in natural and anthropogenic environments, but they are often associated with organic matter and minerals. Under the context of circular economy, metals should be recycled, yet they are difficult to extract for their complex forms in real situations. Based on the protocols of review methodology and the analysis of VOS viewer, there are few reviews on the properties of metal-organic complexes, decomplexation methods, the effect of coexisting ions, the pH influence, and metal recovery methods for the increasingly complicated metal-organic complexes wastewater. Conventional treatment methods such as flocculation, adsorption, biological degradation, and ion exchange fail to decompose metal-organic complexes completely without causing secondary pollution in wastewater. To enhance comprehension of the behavior and morphology exhibited by metal-organic complexes within aqueous solutions, we presented the molecular structure and properties of metal-organic complexes, the decomplexation mechanisms that encompassed both radical and non-radical oxidizing species, including hydroxyl radical (OH), sulfate radical (SO˙4-), superoxide radical (O˙2-), hydrogen peroxide (H2O2), ozone (O3), and singlet oxygen (1O2). More importantly, we reviewed novel aspects that have not been covered by previous reviews considering the impact of operational parameters and coexisting ions. Finally, the potential avenues and challenges were proposed for future research.

Potential roles of the rhizospheric bacterial community in assisting Miscanthus floridulus in remediating multi-metal(loid)s contaminated soils

Phytoremediation technology is an important approach applied to heavy metal remediation, and how to improve its remediation efficiency is the key. In this study, we compared the rhizospheric bacterial communities and metals contents in Miscanthus floridulus (M. floridulus) of four towns, including Huayuan Town (HY), Longtan Town (LT), Maoer Village (ME), and Minle Town (ML) around the lead-zinc mining area in Huayuan County, China. The roles of rhizospheric bacterial communities in assisting the phytoremediation of M. floridulus were explored. It was found that the compositions of the rhizospheric bacterial community of M. floridulus differed in four regions, but majority of them were heavy metal-resistant bacteria that could promote plant growth. Results of bioconcentration factors showed the enrichment of Cu, Zn, and Pb by M. floridulus in these four regions were significantly different. The Zn enrichment capacity of ML was the strongest for Cu and stronger than LT and ME for Pb. The enrichment capacity of LT and ML was stronger than HY and ME. These bacteria may influence the different heavy metals uptake of M. floridulus by altering the soil physiochemical properties (e.g., soil peroxidase, pH and moisture content). In addition, co-occurrence network analysis also showed that LT and ML had higher network stability and complexity than HY and ME. Functional prediction analysis of the rhizospheric bacterial community showed that genes related to protein synthesis (e.g., zinc-binding alcohol dehydrogenase/oxidoreductase, Dtx R family transcriptional regulators and ACC deaminase) also contributed to phytoremediation in various ways. This study provides theoretical guidance for selecting suitable microorganisms to assist in the phytoremediation of heavy metals.

Hydrophilic ZnO/C nanocomposites with superior adsorption, photocatalytic, and photo-enhanced antibacterial properties for synergistic water purification

Owing to the numerous potential applications of ZnO nanomaterials, the development of ZnO-based nanocomposites has become of great scientific interest in various fields. In this paper, we are reporting the fabrication of a series of ZnO/C nanocomposites through a simple "one-pot" calcination method under three different temperatures, 500 ℃, 600 ℃, and 700 ℃, with samples labeled as ZnO/C-500, -600, and -700, respectively. All samples exhibited adsorption capabilities and photon-activated catalytic and antibacterial properties, with the ZnO/C-700 sample showing superior performance among the three. The carbonaceous material in ZnO/C is key to expanding the optical absorption range and improving the charge separation efficiency of ZnO. The remarkable adsorption property of the ZnO/C-700 sample was demonstrated using Congo red dye, and is credited to its good hydrophilicity. It was also found to exhibit the most notable photocatalysis effect due to its high charge transfer efficiency. The hydrophilic ZnO/C-700 sample was also examined for antibacterial effects both in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against MSRA-infected rat wound model), and it was observed to exhibit synergistic killing performance under visible-light irradiation. A possible cleaning mechanism is proposed on the basis of our experimental results. Overall, this work presents a facile way of synthesizing ZnO/C nanocomposites with outstanding adsorption, photocatalysis, and antibacterial properties for the efficient treatment of organic and bacterial contaminants in wastewater.

Effect of photocatalysis on the physicochemical properties of liquid digestate

Antibiotic residues pose a risk to the agricultural application of liquid digestate. In our previous study, photocatalysis was employed to degrade the antibiotics in liquid digestate and observed that the removal efficiency of TC, OTC, and CTC was up to 94.99%, 88.92%, and 95.52%, respectively, at the optimal experimental level, demonstrating the feasibility of this technology. In this study, the liquid digestate after photocatalysis was analyzed to evaluate the effect of photocatalysis on the nutrients, phytotoxicity, and bacterial community of liquid digestate. The results showed that photocatalysis had little effect on the major nutrients TN, TP, and TK in liquid digestate. However, photocatalysis could cause an increase in tryptophan substances as well as soluble microbial by-products and a decrease in humic acid substances in the liquid digestate. The toxicity of liquid digestate after photocatalysis exhibited an increasing trend followed by a decreasing trend, and the liquid digestate after photocatalysis for 2 h had a promoting effect on seed germination and root growth. The richness, diversity, and evenness of bacterial communities in liquid digestate were decreased as a result of photocatalysis. The dominant species in the liquid digestate was dramatically changed by photocatalysis, and the antibiotic concentration also had a major effect on the dominant species in the liquid digestate after photocatalysis. After photocatalysis for 2 h, the dominant species in the liquid digestate changed from Firmicutes to Proteobacteria.

Biosorption kinetics of cerium(III) and cobalt(II) from liquid wastes using individual bacterial species isolated from low-level liquid radioactive wastes

The existence of toxic heavy metals in the aquatic environment has emphasized a considerable exigency to develop several multifunctional biosorbents for their removal. Herein, three individual bacterial species of Cellulosimicrobium cellulans, Bacillus coagulans, and Microbacterium testaceum were successfully isolated from low-level liquid radioactive wastes. Their loading capacities towards cerium and cobalt metal ions were inclusivity inspected under variable operational parameters of pH, primary pollutant concentration, interaction time, temperature, stirring speed, and biosorbent dosage. By analyzing the influence of solution pH, concentration, temperature, biosorbent mass, and agitation speed on the biosorption kinetics, the biosorption process confirms pseudo-second-order kinetic, intraparticle diffusion, and Elovich equation. Remarkably, the isolated Microbacterium testaceum exhibited high loading capacities reaching 68.1 mg g^-1, and 49.6 mg g^-1 towards Ce(III), and Co(II) ions, respectively, at the initial concentration of 2.8 mM, pH 4.5, and 25 °C. Overall, the isolated bacterial species can potentially be offered up as a promising scavenger for Ce(III) and Co(II) from liquid waste effluents.

Intimately coupled photocatalysis and functional bacterial system enhance degradation of 1,2,3- and 1,3,5-trichlorobenzene

Intimate coupling of photocatalysis and biodegradation (ICPB) is considered a promising approach for the degradation of recalcitrant organic compounds. In this work, using Trichoderma with benzene degradation ability coupled with activated sludge as a biological source and sugarcane bagasse cellulose composite as a carrier, the ICPB system showed excellent degradation and mineralization of trichlorobenzene under visible light induction. The biofilm inside the ICPB carrier can degrade and mineralize the photocatalytic products. ICPB increased the degradation efficiency of 1,2,3-TCB and 1,3,5-TCB by 12.43% and 4.67%, respectively, compared to photocatalysis alone. The biofilms inside the ICPB carriers can mineralize photocatalytic products, which increases the mineralization efficiency by 18.74%. According to the analysis of intermediates, the degradation of 1,2,3-TCB in this coupled system involved stepwise dechlorination and ring opening. The biofilm in ICPB carrier evolved to be enriched in Cutaneotrichosporon, Trichoderma, Apiotrichum, Zoogloea, Dechloromonas, Flavihumibacter and Cupriavidus, which are known for biodegradable aromatic hydrocarbon and halogenate. Novel microbial seeds supplemented with Trichoderma-based ICPB seem to provide a new potential strategy for effective degradation and mineralization of TCB.