Adsorption isotherms and kinetics pertinent to modified composite hydrogel adsorbents adopted for heavy metals removal

Abstract

Environmental friendly adsorbents constitute an effective method for heavy metals pollution mitigation. In this work, batch adsorption experiments were conducted for the adsorption of various heavy metals including Cr, Co, Ni and Pb using cost-effective modified adsorbents. These comprise polyacrylate hydrogels prepared using microwave (M)irradiation technique (ACM) or ultrasonic (U) irradiation technique (ACU). Furtherblends of acrylic acid salts with Egyptian kaolin (AKM and AKU) or zeolite (AZM andAZU) were also investigated. The effect of pH and initial concentration on theperformance of the composite hydrogels has been studied. Also, several adsorptionisotherm and kinetic models were studied. AKU revealed the highest maximumadsorption capacities among other investigated composites for all the tested heavy metals.The equilibrium adsorption experiments revealed that Langmuir isotherm model is bestfitted than other models with maximum adsorption capacities of 84.5, 73.3, 61 and 97mg/g for Cr, Co, Ni and Pb, respectively and equivalent results were obtained fromTempkin isotherm for all ions except Ni. Adsorption kinetics of Cr, Co, Ni and Pb usingall the composite hydrogels were best described with the Pseudo-second order kineticmodel.