Removal of Malachite Green from Aqueous Solutions by Perlite

Abstract

Perlite was utilized as an adsorbent for the removal of malachite green from their aqueous solution. The effects of the initial dye concentration, contact time, adsorbent dose, pH, and temperature were studied for the adsorption of malachite green in batch mode. The dye adsorption equilibrium was rapidly attained after 40 min of contact time. Adsorbent was characterized by FTIR, XRD and SEM. The Langmuir and Freundlich isotherm described the adsorption data over the concentration range (20 – 100 mg/L). The rate parameters of the intra particle diffusion were calculated and compared to identify the adsorption mechanisms. The thermodynamic parameters such as entropy change, enthalpy change, and energy of adsorption were calculated to know the nature of adsorption. The negative values of energy of adsorption and the positive values of enthalpy change suggested that the adsorption process is spontaneous and exothermic. Kinetic studies showed that the adsorption process obeyed the pseudo first-order kinetic model.

Adsorption of C.I. Acid Red 97 dye from aqueous solution onto walnut shell: kinetics, thermodynamics parameters, isotherms

“…It is obvious from Fig. 4 that the maximum amount of dye removal took place within the contact time of 60 min, and then, it remained almost constant due to the desorption process and the solution that has reached equilibrium (Govindasmay et al 2009). The fast adsorption at the initial contact time can be explained by the electrostatic attraction, and the slow rate of dye adsorption after 60 min may occur as a result of the slow pore diffusion of the solute molecules into the bulk of the adsorbent (Khaled et al 2009).…”

“…It is essential to realize the adsorption mechanism by determining the zero point charge (pH ZPC ) of the adsorbent (Govindasmay et al 2009). The pH ZPC of the WS was measured by pH drift method.…”

“…It was performed by adjusting the pH of a solution containing 0.01 M NaCl between 2 and 12 using NaOH and HCl, and then, 0.1 g of WS was added to 50 mL of the solution. The final pH was recorded after stabilizing the initial pH after 24 h. The graph of final pH versus initial pH was used to identify pH ZPC that is the point in which both initial and final pH values are equal (Govindasmay et al 2009). In this study, the pH ZPC of the WS was found to be 6.18 (Fig.…”

“…The pH of dye solution is an effective parameter, which controls the adsorption particularly the adsorption capacity. Adsorption of anions is favored at lower pH (\pH zpc ), while the adsorption of cations is favored at a higher pH ([pH zpc ) (Govindasmay et al 2009). The results indicated that acidic pH supported the adsorption of negatively charged AR97 (an anionic dye) on WS, where the surface change of WS was positive (Fig.…”

“…The value of enthalpy of a sorption process is used to determine the chemical or physical sorption. For chemical sorption, enthalpy values vary from 83 to 830 kJ/mol, and for physical sorption, they vary from 8 to 25 kJ/mol (Govindasmay et al 2009). It can be concluded from the low value of DH°that the interaction between AR97 dye molecules and WS is physical.…”