Adsorption of anionic dyes on to waste Fe (III)/Cr (III).

Waste Fe (III)/Cr (III) hydroxide was investigated for the removal of anionic dyes, namely acid brilliant blue (acidic dye) and procion red (reactive azo dye) from aqueous solution. In batch experiments, parameters studied include contact time, adsorbate concentration, pH, adsorbent dose and temperature. Adsorption followed Langmuir isotherm with adsorption capacity of 10.37 and 3.28 mg/g for acid brilliant blue and procion red, respectively. Adsorption kinetic studies showed second order with respect to acid brilliant blue and first order with respect to procion red. Thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were also evaluated.

Surfactant modified coir pith, an agricultural solid waste as adsorbent for phosphate removal and fertilizer carrier to control phosphate release.

The surface of coir pith, an agricultural solid waste was modified using a cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA) and the modified coir pith was investigated to assess the capacity for the removal of phosphate from aqueous solution. Optimum pH for maximum phosphate adsorption was found to be 4.0. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. Kinetic studies showed that the adsorption obeyed second order kinetics. Thermodynamic parameters were evaluated and the overall adsorption process was spontaneous and endothermic. Effect of coexisting anions has also been studied. The feasibility of using spent adsorbent as fertilizer carrier to control phosphate release was also investigated.

Removal of phenol and chlorophenols from water by coir pith carbon: equilibrium and rate studies.

Batch mode studies were conducted to study the removal of phenol, 2,4,6-Trichlorophenol (TCP) and Pentachlorophenol (PCP) from aqueous solution on coir pith carbon by adsorption process under varying experimental conditions such as agitation time, adsorbent dose, pH and temperature. Kinetics of adsorption obeyed second order rate equation and the rate constant was found to be in the range 0.0098-0.0672, 0.0949-0.8801 and 0.172-0.305 g/mg/min for phenol, TCP and PCP respectively. Equilibrium adsorption data follow Langmuir isotherm for phenol and PCP and the adsorption capacities were found to be 48.3 mg and 3.7 mg/g, respectively. For TCP, adsorption followed Freundlich isotherm only. Acidic pH was favorable for the adsorption of all the chlorophenols. Studies on pH effect and desorption show that chemisorption seems to play a major rule in the adsorption process. The positive values of H0 24.99, 18.69, and 8.907 kJ/mol for phenol, TCP and PCP respectively, confirm the endothermic nature of adsorption.