In the current work, nanocomposites of Mg−Al and Mg−Fe layered double hydroxides (LDHs) anchored on silica foam (SF), denoted as MAL/SF and MFL/SF, respectively, were fabricated using a two‐step route. The obtained LDHs/SF nanocomposites were characterized by XRD, TEM, SEM, EDS, elemental mapping, and N2 adsorption‐desorption techniques. Sorption of the heavy‐metal Pb(II) and Cr(VI) on the LDHs/SF was determined at 25 °C and pH 5.5 using a batch technique. In comparison with bulk Mg−Al and Mg−Fe LDHs, the LDHs in the MAL/SF and MFL/SF exhibit significantly enhanced sorption capacities. In addition, the LDHs/SF nanocomposites show a good recyclability for removing heavy metals. The construction of LDHs/SF nanocomposites is an effective strategy for improving the sorption capacity of LDHs, and the nanocomposites are potential sorbents for wastewater treatment.

Industrial heavy metal-contaminated wastewater is one of the main water pollution problems. Adsorbents are a promising method for the removal of heavy metal contaminants. Herein, polyaspartic acid/carboxymethyl poplar sawdust hydrogels (PASP/CMPP) and ascorbic acid/carboxymethyl poplar sawdust hydrogels (VC/CMPP) were prepared by aqueous polymerization using alkalized poplar sawdust (CMPP) as the substrate and PASP and vitamin C (VC) as modifiers. The effective results, provided by the characterization analysis of SEM and BET, indicate that the surface of the PASP/CMPP hydrogel has a larger number of loose pores and a larger pore volume than the VC/CMPP hydrogel. The treatment effects of the two hydrogels on simulated wastewater containing Cd(II) were investigated by a batch of experiments. The results showed that PASP/CMPP had a better adsorption effect than VC/CMPP under the same adsorption conditions. Interestingly, the solid concentration effect was found in the process of sorption kinetics and sorption isotherms. The sorption kinetic curves of Cd(II) on PASP/CMPP were well-fitted by the quasi-second-order kinetics under different adsorbent concentrations. The adsorption conforms to Langmuir and Freundlich adsorption isotherm models. More importantly, PASP/CMPP composites are expected to be used as a new kind of environmental adsorbent for wastewater treatment.

Using Al(OH)3 and Mg(OH)2 as raw materials, MgAl layered double hydroxides (LDHs) modified from birch leaves were prepared by the ball milling-hydrothermal method, denoted as LDHs/BL, and used for the treatment of wastewater containing Cu(II). The morphology, crystal shape, and specific surface area of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), BET-specific surface area analyzer. The results showed that the prepared LDHs/BL composites had good crystal shape, large specific surface area and suitable pore structure. Langmuir and Freundlich adsorption isotherm models were used to analyze the adsorption. The results showed that the adsorption conforms to Freundlich adsorption isotherm model. Under the same adsorption conditions, the adsorption capacity of the LDHs/BL complex was higher than that of LDH, the removal efficiency of the former was 92%, and that of the latter was 68%. The adsorption mechanism includes metal precipitation and isomorphic replacement. More importantly, this study provides a green method to prepare LDHs. LDHs/BL composites are expected to be used as a new kind of environmental adsorbent for wastewater treatment. This work provides a new idea for the utilization of agricultural and forestry wastes.