Multifunctional cellulose fibers for the simultaneous removal of metal cations and anions: Adsorption study

The efficient removal of heavy metals from wastewater is one of the most pressing environmental problems. This study examines the adsorption capacity of phosphorylated cellulose fibers functionalized with (3-aminopropyl)triethoxysilane for Cu²⁺ and C r O 4 2 − ions in aqueous media. The goal is to determine their adsorption capacities, model adsorption isotherms, elucidate adsorption mechanisms and study competitive adsorption. Adsorption kinetics show very rapid adsorption: more than 80 % of contaminants are eliminated within three minutes and equilibrium is reached after 20 min. Adsorption isotherms for Cu²⁺ and C r O 4 2 − were type IV. Two-stage Langmuir and Dubinin-Astakov models were tested, with the latter providing the best fit. The isotherms combine type I and type V behaviors, explained by the presence of two types of active sites on the adsorbent surface, resulting in different adsorbent-adsorbate interactions and sequential or multilayer adsorption. The adsorption capacities of Cu 2 + and C r O 4 2 − by functionalized fibers are around 117.0 mg/g and 97.63 mg/g, respectively. The adsorption of anions occurs via electrostatic interactions between amine groups and chromate, while copper adsorption involves complexation and ion exchange with amine and phosphate groups. Multi-ion adsorption tests confirmed the simultaneous removal of anions and cations. • Dual functionalized lignocellulosic fiber adsorbent. • Phosphorylated and silylated cellulose. • Simultaneous adsorption of metal cations and anions. • Competitive adsorption. • Two-stage isotherms.