Optimization of Lead (II) Adsorption onto Cross-Linked Polycarboxylate-Based Adsorbent by Response Surface Methodology

Due to the harmful effects to environment and public health, lead has to be removed from wastewater. The novelty of this study is the investigation of the adsorption of lead by a cross-linked polycarboxylate-based adsorbent synthesized, the characterization of adsorbent with FTIR, SEM–EDS, XRD and the optimization of the effective parameters such as initial lead concentration, pH and temperature by response surface methodology. In here, Box–Behnken experimental design was applied by using ANOVA-supported Design Expert software. It was statistically confirmed that the surface representing the adsorption process conforms to the reduced cubic model. The common effects of the parameters were determined, and the equation was obtained to predict lead removal under the desired conditions. It was understood that both Langmuir and Freundlich isotherms can be used to describe the adsorption data. The negative free energy of adsorption process indicated the spontaneous reaction. The values of enthalpy and entropy were determined as − 12.57 kJ mol −1 and − 0.036 kJ mol −1 K −1 , respectively. Maximum lead removal reached to 79.7% at the initial concentration of 480.7 ppm, pH 8 and 25 °C. The selectivity of adsorbent in both lead- and cadmium-containing aqueous solution was also studied. Adsorption was found to be in favor of metal ions with higher initial concentration, and lead was adsorbed more by the effect of electronegativity when the concentration of two ions was equal. Desorption experiments of lead showed that the adsorption process was highly chemical and less physical, and only the physical part of it was desorbed.