Evaluation of phosphorylated tamarind nut carbon for the removal of toxic trace metals from aqueous system

Abstract

The presence of heavy metal toxins in water and wastewater is of important concern today due to their adverse effects on living beings. Adsorption by commercial activated carbon has been used for a long time for the removal of organic and inorganic impurities present in water. The present study is aimed at preparing an activated carbon by phosphoric acid treatment of tamarind nut and comparing its characteristics with that of a commercial activated carbon and evaluating the suitability of this material for the removal of toxic heavy metals such as nickel, lead and cadmium from aqueous solutions. Tamarind nut was treated with phosphoric acid in 1:1 weight ratio and the carbonized material was modified by soaking in 1% sodium carbonate and the carbon obtained (PTNC) was compared with commercial activated carbon (CAC). Column studies were carried out using 2.5 cm diameter glass column using PTNC and CAC with an initial metal ion concentration of 200 mg L-1. The break point was set as 0.1 mg per 100 mL for these metal ion solutions. Column regeneration studies were carried out up to 5 cycles of operation using optimum concentration of HCl in case of PTNC and CAC. Kinetic studies were conducted with PTNC and CAC with various initial concentrations of nickel (II), lead (II) and cadmium (II) solutions with carbon dosage of 100 mg / 100 mL. It could be seen from the present investigation that the tamarind nut carbon exhibited a good mechanical strength and abrasion resistance in column studies. The overall adsorption capacity of the PTNC was higher than that of CAC and also exhibited considerable removal capacity of these metal ions when they were present in wastewater. Hence it could be concluded that phosphorylated tamarind nut carbon could effectively be employed for the removal of these toxic metal ions from water and wastewater. newline newline newline