Adsorption characteristics of copper ions on low-rank Pakistani coal

摘要

The adsorption behavior of copper ions on low-rank Pakistani coal has been studied as a function of contact time, nature of electrolytes (HNO3, HCl, H2SO4 and HClO4), amount of adsorbent, concentration of adsorbate and temperature, using batch method. The quantification of copper was made by atomic absorption spectrometric technique. Maximum adsorption was observed at pH 5.0, using 70 g L-1 of adsorbent for 10 mL of 5 mg L-1 copper concentration with equilibration time of 70 min. The adsorption of copper was decreased with the increase in the concentrations of all the acids used. The kinetic data showed an intraparticle diffusion process with sorption being pseudo-second-order. The calculated rate constant k(2) was 15.625 g mg(-1) min(-1). The adsorption data obeyed the Freundlich, Langmuir and Dubinin-Radushkevich isotherms over the copper concentration range of 5-70 mg L-1. The characteristic Freundlich constants, that is, 1 = 0.447 and K = 10.422 mg g(-1) whereas the Langmuir constants Q = 4.242 mg g(-1) and b = 0.014 L mg(-1) have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 11.236 kJ mol(-1) indicating ion-exchange mechanism of chemisorption. The uptake of copper was increased with the rise in temperature (283-333 K). Thermodynamic quantities, that is,Delta G degrees,Delta S degrees and Delta H degrees have also been calculated and discussed for the system. Adsorbent was characterized by using fourier transform infrared spectroscopy (FTIR) and scanning electron microscope before and after the adsorption of copper. Influence of other cations and anions on the adsorption of copper has also been studied.