Low-Cost and Eco-Friendly Adsorbents from Local Waste: Lead Ions Removal by Prunus dulcis hull

Abstract

Contamination of water resources by toxic metal ions, such as lead, poses a serious threat to ecosystems and human health and compromises the biodiversity of contaminated waters. In this context, the search for sustainable and cost-effective remediation strategies is a priority for the scientific community. Among the alternative technologies, pollutants adsorption onto agro-industrial waste materials is gaining increasing attention due to its low environmental impact and economic feasibility [1,2]. This work investigates the potential of Prunus dulcis hull (PDH), an abundant agricultural by-product, as an adsorbent for lead ions from aqueous solutions. The PDH biomass was thoroughly washed and ground into particles of size ranging from 0.1 to 0.2 mm. Then the adsorbent was characterized by ATR-FTIR, SEM-EDX and point of zero charge (pHpzc) experiments. Batch kinetic and isotherm adsorption experiments were performed at different experimental conditions (pH, ionic medium, ionic strength and temperature). Furthermore, the effect of different ligands with different binding groups (methylamine, acetate, and cysteine) on the PDH adsorption ability was investigated. Finally, column experiments including breakthrough curves and adsorption-desorption cycles were performed to study the efficiency in continuous flow and the recyclability of the adsorbent. In the temperature range investigated, the adsorption equilibrium was reached within 200/500 min. The adsorption kinetics was well described by the pseudo second-order model. The adsorption capacity and the affinity of PDH towards Pb2+ ions change with the changing of the experimental conditions of the metal ion solution following the Langmuir isotherm model. Column experiments showed a comparable adsorption behaviour of the adsorbent under equilibrium and non-equilibrium conditions and a good reuse capacity.