NANOCOMPOSITE APPLICATION FOR SELENIUM REMOVAL – PARAMETRIC STUDIES AND KINETIC MODELING

Nano composite material was synthesized using calcium hydroxy apatite and Phoenix Dactlyifera tree powder using wet chemical precipitation method and characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The influence of operating parameters namely initial pH (3 -11), selenium concentration (50 -200 mg L-1 ), nanocomposite dose (0.5 - 6.0 g L-1 ), presence of competitor chloride ion (0 -10 g L-1 ) and agitation speed (0 – 600 rpm) on the metal uptake was studied. A correlation relating nano composite dose and selenium uptake was proposed as selenium uptake = 202.3 (e-0.259* nanocomposite dose) he maximum uptake capacity of the nanocomposite was found to be 57.27 mg g-1 under optimal environmental conditions with an initial selenium concentration of 100 mg L-1 . Monolayer sorption mechanism, proposed by Langmuir isotherm, was found to apply for this process and the isotherm constants were determined. Modified Ritchie second order and pseudo second order models were fitted to the experimental data and pseudo second order model correlated well with rate constant of 1.5 x 10-3 g mg-1 min-1 and maximum uptake capacity of 70.92 mg g-1 at 32 °C with 100 mg L-1 initial metal concentration. Ritchie model rate constant was evaluated as 1.41×10-2 min-1 under similar process conditions

Biosorption of fluoride using Anogeissus dhofarica – effect of process variables and kinetic studies

Abstract In this experimental study, a novel biosorbent was synthesized from Anogeissus dhofarica and applied for defluoridation under batch-shaking conditions. The influence of process variables, namely initial pH (3.0–11.0), fluoride concentration (50–200 mg/L), biosorbent dosage (0.25–8.0 g/L) and agitation speed (0–600 rpm), on the fluoride uptake was studied. Fluoride uptakes increased with increase in fluoride concentration due to enhanced driving force and decreased with increase in biosorbent dose. An empirical relationship, exponential in nature, was proposed between fluoride uptake and biosorbent dose. The pseudo-second-order rate constant (k2) was determined as 0.00474 g/ (mg.min) at 303 K with an initial fluoride concentration of 100 mg/L and the rate constant increased with increase in temperature. The activation energy was determined as 6.023 kJ/mol. The chemisorptive nature of fluoride removal was proven through kinetic modeling. The findings of this research proved the feasibility of industrial application of this novel biosorbent for fluoride removal over a wide range of environmental conditions.</jats:p