Enhanced removal of cadmium from water using bio-sorbents synthesized from branches and leaves of Capparis decidua and Ziziphus mauritiana

Abstract In this work, powdered adsorbents synthesized from branches and leaves of Capparis decidua (CDB) and Ziziphus mauritiana (ZML) are used for the remediation of potentially toxic cadmium (Cd(II)) ions from wastewater. The effects of various operating parameters such as adsorbent dosage, pH, temperature, contact time and initial concentration of cadmium on the adsorption process were evaluated. The maximum adsorption capacity of CDB and ZML was 248.62 mg/g and 235.65 mg/g, respectively, for Cd(II) ions at room temperature, when the optimum pH, adsorbent dosage, contact time and concentration of Cd(II) were 6.0, 0.1 g/100mL, 60 min and 249 mg/L, respectively. Kinetic studies revealed that the bio-sorption process follows a pseudo-second order model (R 2 = 0 . 999 ) for both employed sorbents. The equilibrium data were found to be in good agreement with Freundlich and Langmuir adsorption isotherm in the case of C. decidua and Z. mauritiana, respectively. Thermodynamic analysis revealed that Cd(II) adsorption onto both bio-sorbents was spontaneous and exothermic in nature. The prepared adsorbents also exhibited excellent regeneration potential with a minor loss in the adsorption capacities after six cycles.