Mechanistic insights into soil heavy metals desorption by biodegradable polyelectrolyte under electric field

Synthesis of polydopamine modified MgAl-LDH for high efficient Cr(VI) removal from wastewater

A highly efficient absorbent was developed in this study by modifying polydopamine film on Mg-Al layered double hydroxide (PDA/MgAl-LDH) to remove Cr(VI) from wastewater. The characterization results showed that the polydopamine film was successfully coated on the MgAl-LDH surface. The preparation ratio, pH, and adsorbent dosage influencing absorption by PDA/MgAl-LDH were systematically investigated. The absorption capacity of Cr(VI) by PDA/MgAl-LDH was 87 mg/g. The equilibrium adsorption isotherm of PDA/MgAl-LDH was in good agreement with that of the Langmuir model. Therefore, the pseudo-second-order kinetic model is suitable for describing adsorption kinetics. The interaction between PDA and Cr(VI) and Cr(III) was investigated using density generalized function theory (DFT), which demonstrated that the PDA amino group could provide electrons for Cr(VI) reduction. Hydrogen and covalent bonding were dominant during the chemisorption process of PDA absorbing Cr(VI), the nitrogen of 5,6-dihydroxyindole was the primary active site for absorbing Cr(III), and electrostatic attraction was mainly responsible for Cr(III) absorption. Therefore, PDA/MgAl-LDH has the potential to adsorb and remove Cr(VI) from wastewater.

Efficient and selective removal of Pb2+ from aqueous solution by using an O- functionalized metal-organic framework

Lead (Pb) is one of the most widespread and highly toxic heavy metals in the environment. The design and synthesis of adsorbent materials for the selective and efficient removal of Pb²⁺ from aqueous solution has received much attention. Herein, the ligand 4,4'-azoxydibenzoic acid with the O^- group was elaborately selected to construct a novel Pr-based MOF for Pb²⁺ removal. The as-prepared MOF adsorbents with high stability exhibited ultra-high selectivity for Pb²⁺, even in the presence of various highly concentrated competitive ions (with the ratios from 1 : 5 to 1 : 50). Also, a high uptake capacity (560.26 mg g^-1) can be achieved for the MOF material, due to the availability of sufficient adsorption sites. The strong electrostatic attraction and coordination interaction between the numerous active O^- sites on MOF adsorbents and Pb²⁺ can account for the good adsorption performance for Pb²⁺, which was systematically verified by zeta potential, FT-IR and XPS studies.