A novel method to harvest Chlorella sp via low cost bioflocculant: Influence of temperature with kinetic and thermodynamic functions

In this study, harvesting efficiency (HE) of bioflocculant (egg shell) was observed with variation in flocculent concentrations (0-100 mg L-1), temperature (30 degrees C, 35 degrees C 40 degrees C, 45 degrees C and 50 degrees C) and variable contact time (0-50 min). It was found maximum (approximate to 95.6%) with 100 mg L-1 bioflocculant concentration whereas influence of temperature was also observed with optimized concentration of bioflocculant (100 mg L-1) at 40 degrees C (approximate to 98.1%) and 50 degrees C (approximate to 99.3%), in 30 min of contact time. Significant changes in algal cell structures were also analyzed after exposure to various temperatures with microscopy, SEM (Scanning electron microscopy) and EDS (Energy dispersive X-ray spectroscopy) images with and without bioflocculant. The experimental data was found to be a good fit with pseudo-second order kinetic model. The thermodynamic functions such as Delta G (Gibbs free energy), Delta H (enthalpy), Delta S (entropy) were also determined. The negative value of Delta G and positive value of Delta H and Delta S shows the spontaneous and endothermic nature of flocculation process. (C) 2016 Elsevier Ltd. All rights reserved.