The kinetics of nickel-fulvate (Ni-FA) reaction with sewage effluents irrigated soils between 0 to 144 h conformed to first order reaction. As predicted by kinetic model, the kinetic constant for the loss of Ni from Ni-fulvate varied from 1105 to 1887 mol h−1 (av. 1424 mol h−1) at 15°C, from 1179 to 1828 mol h−1 (av. 1555 mol h−1) at 30°C and from 1175 to 2317 mol h−1 (av. 1709 mol h−1) at 45°C. These results revealed that rate of Ni-fulvate reaction in soils increased with increasing temperature indicating rates of Ni-FA reaction were temperature dependent. The rate of loss of Ni from Ni-FA by competing ions was positively and significantly correlated with organic carbon (r = 0.512*). The half life of residence of Ni-FA reaction in soils ranged from 3.7×10−4 to 6.3×10−4 h (av. 4.98×10−4 h) at 15°C, from 3.6×10−4 to 5.9×10−4 h (av. 4.53×10−4 h) at 30°C and from 3.0×10−4 to 6.9×10−4 h (av. 4.55×10−4 h) at 45°C. The half life time of residence of Ni-FA in soil decreased with increasing temperature. The average diffusion coefficient of Ni increased from 4.58×10−6 to 7.04×10−6 cm2 sec−1 with increasing temperature from 15 to 45°C indicating that diffusion is temperature controlled reaction.
Nickel-fulvate, kinetics of reaction, sewage sludge, rate constant, diffusion
