Organic and inorganic phosphonates often co-exist in municipal sewage, and it is a challenge to remove them simultaneously. Nanoparticle Fe₃O₄ (Fe₃O₄ NPs) has attracted significant attention due to its high adsorption activity, low cost, environmental friendliness, and magnetic separation. Herein, the adsorption performance and mechanism of hydroxyethylidene diphosphonic acid (HEDP) and orthophosphate (PO₄³⁻) onto Fe₃O₄ NPs were systematically investigated. When the dosages were 0.4 g/L, the removal efficiencies of HEDP and PO₄³⁻ reached 96.3% and 95.1%, respectively. pH had no significant impact on the adsorption, whereas the presence of HCO₃⁻/CO₃²⁻ markedly suppressed the removal of HEDP and PO₄³⁻. The adsorption of HEDP and PO₄³⁻ onto Fe₃O₄ NPs conformed to the pseudo-second-order kinetics and Langmuir isotherm models in single and binary P systems. HEDP consistently inhibited the removal of PO₄³⁻ in the binary P system. The adsorption mechanisms were primarily driven by the combined effect of electrostatic attraction, hydrogen bonding, and coordination complexation. DFT molecular simulation showed higher adsorption energy between HEDP and Fe₃O₄ NPs, and the simulation outcomes were in excellent agreement with the experimental data. Although the adsorption of HEDP and PO₄³⁻ was competitive, total phosphorus in the effluent of municipal sewage could still meet the discharge standard.

In a hybrid microbial-inorganic catalysis system, H₂ evolution reaction (HER) electrocatalysts are coupled with microorganisms to achieve the highly efficient conversion of CO₂ to value-added chemicals using H₂ as an electron mediator. However, currently developed HER electrocatalysts suffer from poor biocompatibility, hindering the performance of the system. This study presents a N- and Si-doped polythiophene nanocomposite (PTh-NSi) as a nonmetal HER electrocatalyst with biocompatibility for use in a hybrid microbial-inorganic catalysis system. By coupling PTh-NSi with Ralstonia eutropha H16, conversion of CO₂ to poly-β-hydroxybutyrate with a maximum yield of 662.99 ± 27.46 mg/L was achieved. The PTh-NSi electrocatalyst demonstrated HER performance in bacterial media, minimal reactive oxygen species production, and no heavy metal ion leaching, ensuring biocompatibility with R. eutropha H16. The interactions between PTh-NSi and R. eutropha H16 were revealed. This work highlights an approach to designing biocompatible catalysts for hybrid microbial-inorganic catalysis systems, offering the potential for sustainable CO₂ conversion.

Increased attention has been attracted to saline–alkali soil amelioration due to the growing serious salinization of soils in the world. Lithium slag (LS) is an acid by-product of lithium production with potential properties to ameliorate alkalinity in saline–alkali soils. In this study, LS was reused as a saline–alkali soil amendment and potted plant experiments in a greenhouse were performed to evaluate the effect of LS application on the soil amelioration and the growth of vegetables (roquette and radish) in the saline–alkali soil during the 5-week growth period. LS was added at the amount of 0.5%, 1.0%, 2.0%, 5.0%, 8.0% and 10.0% (w/w) levels. Results showed that saline–alkali soil pH dropped obviously with the increase in LS application. Accordingly, the germination, survival and growth of roquette and radish were significantly improved by LS addition, especially at the optimum amount of 0.5% and 1.0% (w/w) in the saline–alkali soil. In contrast to the untreated saline–alkali soil, LS addition at 0.5% and 1.0% (w/w) levels increased the roquette’s height by 49.7% and 36.1% and increased the radish’s height by 54.6% and 53.7%, respectively. However, the soil electrical conductivity (EC) and soluble salt content increased with the addition of LS, and the salt stress induced by excessive LS (over 5.0% level) could inhibit the growth of plants. This study proposes a new way for the effective application of LS in the amelioration of saline–alkali soil in order to realize environment and resource sustainability.

Carbon xerogel is a nano-scale adsorption material with abundant mesopores and large adsorption capacity. A series of mesoporous carbon xerogels (MCX) were synthesized in the process of polycondensation of resorcinol and formaldehyde using different resorcinol/sodium carbonate catalyst molar ratios (R/C = 100~3000). And the adsorption behavior of the MCX for the azo dye reactive blue 13 (RB13) from dyeing wastewater was investigated in this study. Results showed that variations in both specific surface area and pore size distribution of MCX were closely related to the amount of catalyst. The MCX exhibited maximal surface area, abundant mesoporosity, and highest adsorption capacity for RB13 when the molar ratio of R/C was 1000. The adsorption of RB13 by MCX1000 proceeded rapidly in the first 50 min and reached equilibrium in 180 min. The adsorption process was exothermic, spontaneous, and can be well fitted by the pseudo-second-order and Temkin models, with the maximum sorption capacity of 184.36 mg·g^-1. The adsorption of RB13 onto MCX was attributed to physicochemical adsorption. The main adsorption mechanisms of the MCX for RB13 were the electrostatic interaction, hydrogen bonding and van der Waals forces between dye molecules and functional groups, such as -OH, and -C-O, etc.

Simultaneous adsorption of organic phosphonate

Dewatering is a crucial stage in the treatment of sludge since it directly increases capacity and lowers the cost of subsequent handling. Enhanced dewatering of printing and dyeing sludge was experimentally investigated with combined conditioners of sludge-derived biochar and ferric chloride (FeCl3) in this study. Results showed that the optimal conditioner dosages were: FeCl3 of 3% dry sludge (DS) and biochar of 60% DS. Compared with raw sludge, the sludge specific resistance to filtration (SRF) decreased by 77.14%, and the moisture content of sludge decreased from 85.38% to 67.08%. In addition, the chemical oxygen demand (COD), turbidity and chromaticity of supernatant decreased by 32.50%, 89.20% and 77.50%, respectively. It was found that the synergistic effect existed between the two conditioners. The possible mechanism was that FeCl3 aggregated small sludge particles to form large flocs and improved the dewatering performance of sludge, while biochar helped to build an incompressible and permeable sludge cake to further improve the sludge dewaterability due to its relatively hydrophobicity and large specific surface area. Therefore, combined addition of FeCl3 and biochar might be a promising conditioning method to enhance textile sludge dewaterability.