Evaluation of Lead Removal from Aqueous Solutions with Nano-Composite of Layered Double Hydroxides Coated on Magnetic Activated Carbon

Contamination of soils and aquatic environments with heavy metals is a serious and growing problem. Some pollutants, such as heavy metals like lead, are persistent, and most of these metals have high toxicity and are a significant environmental concern. Therefore, the present study aimed to remove lead from aqueous solutions by layered double hydroxide (LDH) nanocomposite deposited on magnetically activated carbon.

This experimental laboratory study was conducted on a small scale in a laboratory setting, and the samples were synthetically prepared. In this study, the effect of pH (4-10), adsorbent concentration (0.1-3 g/l), contact time (10-120 minutes), and initial concentrations of lead (5-20 mg/l) on the removal of lead ions was investigated. Process performance was evaluated based on the percentage of lead ion removal responses. Determination of the number of experiments, statistical analysis of the data, and optimization of lead ion removal were performed using the central composite design and surface-response method.

The effect of exploitation indicators on lead removal efficiency according to the analysis of variance (ANOVA) table showed that, apart from lead concentration, the rest of the indicators were significant, and respectively, the intensity of the effect and the highest value of F included LDH concentration, contact time, and pH. Lead removal efficiency was obtained 96.11% in optimal conditions with pH = 6.73, a reaction time of 67.71 minutes, a concentration of LDH nanocomposite adsorbent of 2.10 g/l, and an initial lead concentration of 10.98 mg/l. In these conditions, the model's utility was 100%. Based on the results, the highest correlation of adsorption kinetics was observed with the quadratic model. This model was selected as the most suitable to describe the kinetic behavior of LDH adsorbent deposited on magnetically activated carbon in the adsorption of lead ions from aqueous media.

The LDH adsorbent deposited on magnetically activated carbon is a suitable material for removing lead ions from aqueous solutions. Moreover, the utilization of a central composite design and surface response methodology to optimize the key variables in the lead ion removal process through adsorption is commendable.