Kinetics, mechanism, and thermodynamics of lanthanum adsorption on pectin extracted from durian rind

The rare-earth elements in aqueous waste streams have received great attention due to their potential to pollute the environment Lanthanum is one of the most used rare-earth elements in industries and disposed as waste. Several efforts have been devoted to remove lanthanum from waste water systems. This study was focused on the adsorption of lanthanum from aqueous solutions by using pectin extracted from durian rind, which is home and industrial waste of durian fruit Adsorption experiments were carried out in batch method, and the effects of contact time, initial concentration of lanthanum ion, pH of medium, pectin dosage, and temperature on the adsorption efficiency were investigated. The kinetics, mechanism, and thermodynamics of lanthanum adsorption on the pectin were also evaluated. The results demonstrated that the pectin as a cost-effective biosorbent could remove lanthanum with efficiency as high as 41.2 mg/g (at the optimum conditions: pH 4.0, 25 degrees C, 90 min). The adsorption process of lanthanum on the pectin is well described by either Freundlich or Temkin isotherm model, indicating that adsorption occurs mainly on multilayers and heterogeneous surfaces of pectin. Thermodynamic quantities suggested that the adsorption of lanthanum on the pectin was exothermic and spontaneous, and the reaction was feasible. We also showed that the spent adsorbent can be regenerated up to a limited number of times, upon strong base treatment.