Recovery and Recycling of Zn(II) from Wastewater by Scenedesmus sp. MCC 26 Isolated from a Heavy Metal Contaminated Site

This study evaluated the potential of Scenedesmus sp. MCC 26 as a new cost effective and efficient alternative for removing Zn(II) ions from viscose industrial effluent. Scenedesmus sp. MCC 26 (green microalgae) was isolated from a metal contaminated site and investigated for biosorption of Zn(II) from simulated viscose industrial effluent. Different biosorption parameters such as effect of pH (2-7), initial Zn(II) ion concentration (0-600mg/L) and contact time (0-120min) were investigated in order to optimize the process. The maximum absorption (142.85mg/g) by the microalgal biomass was observed at pH 6 within 60min of contact time at 28 degrees C. Biosorption process was found to be rapid (6mg of Zn/g biomass per min) for initial 10min followed by a slower phase (0.6mg of Zn/g biomass per min). The absorption data fitted well with Langmuir isotherm (q(max)=142.85mg/g, r(2)=0.973) and Freundlich isotherm (k(f)=1.447, r(2)=0.992). Treatment of Zn(II) loaded biomass with 0.1M H2SO4 showed almost 99% recovery of zinc which can be reused in the industrial processes. After first cycle of Zn(II) removal and recovery, the same biomass was tested for its reusability in repeated cycles. The results showed that the same biomass can be used minimum for five cycles of Zn(II) absorption and recovery with similar efficiency.