Removal of strontium from aqueous solutions using coir pith as biosorbent: kinetic and equilibrium studies

Coir pith a natural, lignocellulosic, low-cost, agricultural by-product has been evaluated as a sorbent to remove strontium from aqueous solutions. Sorption studies were performed in a batch mode by varying the experimental parameters such as solution pH, initial metal ion concentration and contact time. The extent of strontium sorption was found to increase with increase in initial metal ion concentration and contact time. The optimum sorption of Sr(II) on coir pith was achieved in the pH range of 5-8. Kinetic studies showed that the strontium sorption process was rapid and followed pseudo second-order kinetics. Equilibrium data were evaluated using Langmuir and Freundlich adsorption isotherms. Maximum sorption capacity of coir pith for Sr(II) was found to be 87.16 mgg-1 in the studied concentration range. Repeated sorption-desorption cycles were performed to examine the reusability and metal recovery efficiency of the biosorbent. Sr(II) could be desorbed almost completely from the spent coir pith using HCl or EDTA solutions within 1h. Quantitative removal of strontium was obtained from spiked ground water samples. The studies revealed that, coir pith is a promising biosorbent for Sr(II) removal from aqueous solutions owing to its low cost and high uptake capacity.