Enhanced effect and mechanism of nano Fe-Ca bimetallic oxide modified substrate on Cu(II) and Ni(II) removal in constructed wetland

Performance and mechanism of nano Fe-Al bimetallic oxide enhanced constructed wetlands for the treatment of Cr(VI)-contaminated wastewater

Enhancing the synergistic interactions between substrates and microorganisms in constructed wetlands (CWs) represents a promising approach for treating heavy metal-contaminated wastewater. Multifunctional nanomaterials may play a significant role in this process. However, their impacts and mechanisms in this context remain unclear. In this study, artificial zeolite spheres loaded with Fe-Al double metal oxide (Fe-Al-NBMO) were synthesized and utilized in the CW to treat Cr(VI)-contaminated wastewater. Adsorption experiments demonstrated that the adsorption capacity of Fe-Al-NBMO loaded substrate for Cr(VI) was 988.43 mg/kg at an initial concentration of 30 mg/L, 361, and 37 times higher than that of gravel and carrier, respectively. The CW experiment indicated that the Cr(VI) effluent concentration in CW-ZL with Fe-Al-NBMO substrate did not exceed the integrated wastewater discharge standard (GB8978-1996) (0.5 mg/L) at an influent concentration of 50 mg/L. The introduction of the Fe-Al-NBMO substrate promoted microbial growth and increase the Extracellular Polymeric Substances (EPS) and other metabolite contents, thereby enhancing the microbial adsorption of Cr(VI). Furthermore, the removal performance of Cr(VI) was enhanced by the increase in resistant microorganisms (Hyphomicrobium and Rhodopseudomonas) and functional genes. Notably, metaproteomic analysis revealed that the elevated abundance of NADH-quinone oxidoreductase (nuoB, nuoC, nuoD, nuoE, nuoF, and nuoG), reductive coenzymes (fbp, ALDO, mcrA, and cdhC), metabolic pathways of sulfur (Cysp), and glutathione transferase (GsiB, frmA, and gfa) contributed to Cr(VI) removal. Our results provide a robust strategy for treating Cr(VI)-contaminated wastewater by CWs with Fe-Al-NBMO loaded substrate.

Adsorption of Ni(II) from Aqueous Solution by Wheat Straw Modified with Mercaptopropionyl Functional Groups

Mercaptopropionyl wheat straw (MPWS) was prepared as an adsorbent by modifying wheat straw with mercaptopropionyl groups, and the ability of MPWS for the removal of Ni(II) from aqueous solution was examined. The removal of Ni(II) by using MPWS was identified through investigating the impacts of MPWS dosage, adsorption temperature, and adsorption time. Different models for the adsorption isotherm and kinetics were utilized to fit the experimental results and elucidate the mechanism of MPWS for Ni(II). Environmental interference factors, including initial Ni(II) concentration, pH value, inorganic matters, and organic matters in wastewater, were examined to evaluate the antienvironmental disturbance capability of MPWS during Ni(II) adsorption. A removal rate of Ni(II) as high as 99.02% was achieved at pH 6.0 with an adsorption temperature of 30 °C and a contact time of 100 min. The experimental results exhibited excellent alignment with both pseudo-second-order kinetic model, Freundlich isothermal model, Redlich-Peterson model, and Hill model. Furthermore, coexisting substances in the environment could inhibit the adsorption process of Ni(II) by MPWS; however, this inhibition could be mitigated or eliminated by increasing the amount of absorbent MPWS. Overall, MPWS displays remarkable resistance against environmental interference during its application for removing Ni(II) from wastewater.

Electrode functional microorganisms in bioelectrochemical systems and its regulation: A review

Bioelectrochemical systems (BES) as environmental remediation biotechnologies have boomed in the last two decades. Although BESs combined technologies with electro-chemistry, -biology, and -physics, microorganisms and biofilms remain at their core. In this review, various functional microorganisms in BESs for CO2 reduction, dehalogenation, nitrate, phosphate, and sulfate reduction, metal removal, and volatile organic compound oxidation are summarized and compared in detail. Moreover, interrelationship regulation approaches for functional microorganisms and methods for electroactive biofilm development, such as targeted electrode surface modification, chemical treatment, physical revealing, biological optimization, and genetic programming are pointed out. This review provides promising guidance and suggestions for the selection of microbial inoculants and provides an analysis of the role of individual microorganisms in mixed microbial communities and its metabolisms.

Ecological restoration orientated application and modification of constructed wetland substrates

Constructed wetlands (CWs) have gained recognition as an environmentally friendly and cost-efficient option for treating municipal, industrial, and agricultural wastewater. They treat wastewater by harnessing the combined action of physical, chemical, and biological processes within substrates, plants, and microorganisms, with substrates exerting the greatest influence on the life cycle and purification efficiency of the system. This review provides an in-depth discussion on the development and performance of various substrate types used in CWs, including natural materials, ore-based materials, biomass materials, waste materials, and modified and novel materials. Key substrate modification techniques are summarized in detail, such as acid-base treatment, metal doping, compound modification, and heat treatment, which enhance structural and functional properties to improve pollutant removal. The paper also systematically explores the mechanisms of introducing methods like inorganic electronic enhancement and describes their applications in improving pollutant removal in CW systems. This review provides a holistic evaluation of substrate classification and optimization strategies and a prospective discussion of their challenges and opportunities in practical applications. It contributes to the creation of more efficient and sustainable materials for CW systems and provides theoretical support for selecting and optimizing substrates, thereby driving progress in wastewater treatment technology.

Luminescent carbon dots-rooted polysaccharide crosslinked hydrogel adsorbent for sensitive determination and efficient removal of Cu2

In this study, a novel luminescent carbon dot-rooted polysaccharide hydrogel (CDs@CCP hydrogel) was prepared by crosslinking cellulose, chitosan (CS), and polyvinyl alcohol (PVA) for simultaneous fluorescent sensing and adsorption of Cu2+. The crosslinking of these low-cost, polysaccharide polymers greatly enhance the mechanical strength of the composite hydrogel while making the polysaccharide-based adsorbent easy to reuse. This composite hydrogel exhibited an excellent adsorption capacity (124.7 mg∙g-1) for residual Cu2+ in water, as well as a sensitive and selective fluorescence response towards Cu2+ with a good linear relationship (R2 > 0.97) and a low detection limit (LOD) of 0.02 μM. The adsorption isotherms, adsorption kinetics, and thermodynamics studies were also conducted to investigate the adsorption mechanism. This composite hydrogel offers an efficient tool for simultaneous monitoring and treatment of Cu2+ from wastewater.

Peroxymonosulfate activation by walnut shell activated carbon supported nano zero-valent iron for the degradation of tetracycline: Performance, degradation pathway and mechanism

In this study, activated carbon (WS-AC) was prepared from walnut shell. Nano-zero-valent iron (nZVI) was loaded on walnut shell activated carbon by liquid phase reduction method and used as catalyst (WS-AC/nZVI) to activate peroxymonosulfate (PMS) to efficiently degrade tetracycline (TC) in solution. The composite material with a mass ratio of WS-AC to nZVI of 1:1 has the highest catalytic performance for activating PMS to degrade TC. The results showed that under the conditions of TC concentration of 100 ppm, PMS dosage of 0.2 mM and WS-AC/nZVI dosage of 0.1 g/L, the removal efficiency of TC could reach 81%. Based on quenching experiments and electron spin resonance (EPR), it was verified that •OH, SO4•- and 1O2 bound on the catalyst surface were the main reactive oxygen species during the reaction. The intermediate products of TC were identified by liquid chromatography-mass spectrometry (HPLC-MS) and DFT calculation, and the possible degradation pathway of TC was proposed. The catalyst still maintained high removal efficiency of TC after four cycles of experiments, and the minimal iron loss on the surface of the catalyst indicated that it had good stability. The efficient and stable WS-AC/nZVI activated PMS showed great potential in the degradation of antibiotics.