Kinetic and equilibrium studies of chromium (VI) biosorption by spent macroalgae Polysiphonia urceolata and Chondrus ocellatus

Abstract

The removal of chromium (VI) from aqueous solutions by spent Polysiphonia urceolata and Chondrus ocellatus was investigated with respect to initial pH, amount of biosorbent, initial heavy metal concentrations and temperature. The Cr(VI) removal process was influenced significantly by variations in pH, and the optimum pH was determined to be about 2.0. The optimum algal dosage was 4 g/L and maximum biosorption was achieved at 45 °C in the experiment. The rate of Cr(VI) removal was relatively high in the first 40 min, and biosorption equilibriums were rapidly established in about 60 min for P. urceolata and 40 min for C. ocellatus. The biosorption kinetics followed well a pseudo-second-order model. Adsorption equilibriums were well described by Langmuir and Freundlich isotherm models. The maximum adsorption capacities were 170.6 mg/g for P. urceolata and 113.4 mg/g for C. ocellatus at 298 K and pH 2.0. Fourier transform infrared spectroscopy suggested that amino, hydroxy, C˭O and C–O groups could be involved in the biosorption of Cr(VI) onto P. urceolata and C. ocellatus.