Phosphorus-rich biochar modified with Alcaligenes faecalis to promote U(VI) removal from wastewater: Interfacial adsorption behavior and mechanism

Enhanced nitrate removal in aquatic systems using biochar immobilized with algicidal Bacillus sp. AK3 and denitrifying Alcaligenes sp. M3: A synergistic approach

This study investigates the effectiveness of biochar immobilized with algicidal Bacillus sp. AK3 and denitrifying Alcaligenes sp. M3 in mitigating harmful algal blooms (HABs) and reducing nitrate pollution in aquatic environments. Over a six-day period, we analyzed changes in algal bloom-forming Microcystis density, chlorophyll-a levels (indicative of algal biomass), nitrate concentration, and microbial community composition in water treated with biochar and Bacillus sp. AK3 and Alcaligenes sp. M3-immobilized biochar. In water treatment using the AK3 and M3-immobilized biochar, Microcystis density decreased from 600,000 cells/mL to 80,000 cells/mL, and chlorophyll-a concentrations also substantially reduced, from 85.7 µg/L initially to 42.8 µg/L. Nitrate concentrations in the AK3 and M3-immobilized biochar treatment significantly decreased from approximately 23 mg/L to around 14 mg/L by Day 6, demonstrating the enhanced denitrification capabilities of the immobilized Alcaligenes sp. M3 and associated bacterial communities. The results also showed significant shifts in bacterial communities, with a decrease in Microcystis, highlighting the specific algicidal activity of Bacillus sp. AK3. The study underscores the potential of biochar-based treatments as a sustainable and effective approach for improving water quality and mitigating the environmental impacts of nutrient pollution and HABs.

Fabrication of Carboxylate-Functionalized 2D MOF Nanosheet with Caged Cavity for Efficient and Selective Extraction of Uranium from Aqueous Solution

The efficient removal of radioactive uranium from aqueous solution is of great significance for the safe and sustainable development of nuclear power. An ultrathin 2D metal-organic framework (MOF) nanosheet with cavity structures was elaborately fabricated based on a calix[4]arene ligand. Incorporating the permanent cavity structures on MOF nanosheet can fully utilize its structural characteristics of largely exposed surface area and accessible adsorption sites in pollutant removal, achieving ultrafast adsorption kinetics, and the functionalized cavity structure would endow the MOF nanosheets with the ability to achieve preconcentration and extraction of uranium from aqueous solution, affording ultrahigh removal efficiency even in ultra-low concentrations. Thus, more than 97% uranium can be removed from the concentration range of 50-500 µg L-1 within 5 min. Moreover, the 2D nano-material exhibits ultra-high anti-interference ability, which can efficiently remove uranium from groundwater and seawater. The adsorption mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) analysis, and density functional theory (DFT) calculations, which revealed that the cavity structure plays an important role in uranium capture. This study not only realizes highly efficient uranium removal from aqueous solution but also opens the door to achieving ultrathin MOF nanosheets with cavity structures, which will greatly expand the applications of MOF nanosheets.

Exploring recyclable alginate-enhanced GCN-LDO sponge for U(VI) and Cd(II) removal: Insights from batch and column studies

Developing effective water treatment materials, particularly through proven adsorption methods, is crucial for removing heavy metal contaminants. This study synthesizes a cost-effective three-dimensional material encapsulating graphitic carbon nitride-layered double oxide (GCN-LDO) in sodium alginate (SA) through the freeze-drying method. The material is applied to remove uranium (U(VI)) and cadmium (Cd(II)) in real water systems. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analyses conclusively verified the elemental composition and successful encapsulation of GCN-LDO within the SA matrix. Removal effectiveness was tested under various conditions, including adsorbent dose, ionic strength, contact time, temperature, different initial pollutant concentrations, and the impact of co-existing ions. The adsorption of U(VI) and Cd(II) conformed to the pseudo-second-order (PSO) kinetic model, signifying a chemical interaction between the sodium alginate-graphitic carbon nitride-layered double oxide (SA-GCN-LDO) sponge and the metal ions. The Langmuir isotherm indicated monolayer, homogeneous adsorption for U(VI) and Cd(II) with capacities of 158.25 and 165.00 mg/g. SA-GCN-LDO recyclability was found in up to seven adsorption cycles with a removal efficacy of 70%. The temperature effect study depicts the exothermic nature of the U(VI) and Cd(II) ion removal process. Various mechanisms involved in U(VI) and Cd(II) removal were proposed. Further, continuous fixed bed column studies were performed, and Thomas and the Yoon-Nelson model were studied. These insights from this investigation contribute to advancing our knowledge of the material's performance within the context of U(VI) and Cd(II) adsorption, paving the way for optimized and sustainable water treatment solutions.