Rapid and efficient lead(ii) ion removal from aqueous solutions using Malva sylvestris flower as a green biosorbent

Abstract

In this study, for the first time, Malva sylvestris flower as a natural and green biosorbent was used for rapid and efficient removal of toxic Pb²⁺ ions from aqueous solutions. The proposed biosorbent is very cheap and is found in most parts of the world. Various influential parameters including solution pH, biosorbent particle size and dosage, contact time, stripping speed, initial metal ion concentration and temperature were investigated by Taguchi experimental design to optimize the biosorption performance. Under optimized conditions (pH, 4.5; sorbent particle size, mesh number 30; sorbent dosage, 0.2 g; contact time, 15 min; stripping speed, 500 rpm; initial metal ion concentration, 60 mg L⁻¹; temperature, 55 °C), the maximum biosorption capacity of Malva sylvestris was 25.64 mg g⁻¹. The obtained data fitted better to a Langmuir isotherm compared to a Freundlich isotherm model. The interfering effect of some common cations on the adsorption capacity of Pb²⁺ was investigated, and there was no significant interference from the mentioned cations. The experimental adsorption data were fitted to a pseudo-second order kinetic model with an initial adsorption rate constant of 204.08 mg g⁻¹ min⁻¹. The changes of adsorption with time showed that most of the process is completed within the first 3 minutes.