Synthesis of Fe-Zn-Al Layered double oxide for effective adsorptive removal of trace metal(loid)s: optimisation, isotherms, kinetics and application to real water samples

The layered double oxides (LDO) have gained attention as sorbets for decontaminating metal (loid)s for wastewater treatment. These materials are prepared from LDH by thermal treatment, whereby LDHs are calcined to remove interlayer anions. This study synthesised Fe-Zn-Al-LDO from Fe-Zn-Al LDH via thermal treatment to decontaminate As, Cd, and Pb in wastewater. The synthesised Fe-Zn-Al LDO was characterised using various analytical characterisation techniques. The transmittance electron microscopy (TEM) results showed that Fe-Zn-Al-LDO had spherically shaped particles with an average size of 12.1 ± 1.7 nm. The Brunauer–Emmett–Teller (BET) surface area and pore volume of the Fe-Zn-Al LDO material were 88.1 m²/g and 0.35 cm³/g. Under optimum conditions, Fe-Zn-Al LDO adsorbent had an excellent adsorption efficiency for As, Cd and Pb, with maximum adsorption capacities of 233 mg/g, 204 mg/g and 256 mg/g, respectively. The kinetics and isotherm studies revealed that the adsorption process of the analytes onto Fe-Zn-Al LDO adsorbent followed pseudo-second order and Freundlich isotherm models. The Fe-Zn-Al LDO materials were utilised as an adsorbent to remove As, Cd and Pb from groundwater and surface water spiked with 1000 µg/L of analytes, and the results showed that the adsorbent reduced the concentrations of these analytes to levels below the acceptable contamination levels. With the systematic study of adsorptive removal of trace metal(loid)s using Fe-Zn-Al LDO adsorbent, a promising adsorption technology was developed to address pollution of drinking water sources.