Simultaneous preconcentration and determination of nickel and cobalt using functionalised mesoporous silica spheres by ICP-OES

In this work functionalised mesoporous silica spheres have been utilised for the simultaneous preconcentration of nickel and cobalt. The silica spheres (SiSPs) prepared by the sol-gel method were functionalised with sodium diethyldithiocarbamate (DDTC-SiSPs). They were characterised by SEM, TEM, XRD, FTIR, CHN and nitrogen adsorption. The adsorption efficiency of DDTC-SiSPs was examined by batch equilibrium technique. The DDTC-SiSPs showed 100% adsorption for Ni (II) and Co (II). The effect of changing variables such as pH, shaking time, sample volume, preconcentration factor, eluent type and volume were investigated so as to obtain maximum recovery with high selectivity over interfering ions. The maximum adsorption capacity was found to be 15.15mg g(-1) and 11.80mg g(-1) for Ni (II) and Co (II) respectively using DDTC-SiSPs. 100% recovery was achieved with 5mL of 2M HNO3. The maximum preconcentration factor was 400 and the 3 sigma limits of detection were 0.201 mu g L-1 and 0.198 mu g L-1 for Ni (II) and Co (II) respectively. Thermodynamic studies showed that adsorption of Ni (II) and Co (II) on DDTC-SiSPs is exothermic with enthalpy changes of -0.514KJ mol(-1) and -0.854KJ mol(-1) for Ni (II) and Co (II) respectively. The method was applied to the preconcentration and determination of Ni (II) and Co (II) from tap, river and sea water.