Complexation equilibrium studies of Cu2+, Cd2+ and Pb2+ ions onto ethylenediamine quaternised Artocarpus heterophyllus L. seeds from aqueous solution

Abstract

Heavy metals contamination in drinking water is of great concern because of their toxicity and nonbiodegradability. Therefore, their removal is paramount. Recently, adsorption has gained a great attention from researchers due to availability of the materials and associated capacity compared to conventional methods of water treatment. Various chemical treatment methods have been employed to boost the capacity of the adsorbents, one of them being the use of ethylenediamine. In this study, a novel quaternised adsorbent was synthesized for complexation of Cu2+, Cd2+ and Pb2+ ions from aqueous solution. Raw Artocarpus heterophyllus L. seeds were chemically modified with thionyl chloride followed by ethylenediamine. Both raw and quaternised adsorbents were characterized by FTIR and applied for equilibrium complexation batch experiments. Effect of pH, contact time, agitation speed, adsorbent dosage and initial concentration were investigated. FTIR results showed that amino groups were successfully anchored into the quaternised adsorbent and this increased its complexation capacity. Batch results indicated that complexation of the three metal ions was at optimal at pH values between 4.2 and 6.4. Contact time of 20 minutes and 15 minutes for raw and quaternised adsorbents respectively. Agitation speed of between 150 rpm and 175 rpm. Raw and quaternised dosage of 15 mg and 10 mg; 13 mg and 10 mg; 15 mg for Cu2+, Cd2+ and Pb2+ ions respectively and optimal concentration of 30 ppm. Equilibrium experimental data fitted well in Langmuir isotherm with adsorption capacities of 21.3220 mg g -1 , 19.6850 mg g -1 and 21.8818 mg g -1 for raw and 33.7838 mg g -1 , 25.1256 mg g -1 and 34.0136 mg g -1 for quaternised adsorbent for Cu2+, Cd2+ and Pb2+ions respectively implying a chemisorption mechanism. The results confirmed potentiality of Artocarpus heterophyllus L. seeds for heavy metal ions removal from aqueous solutions