Investigation of the possible use of oil palm calyx in the treatment of wastewaters polluted with dyes

This study explored oil palm calyx (OPCA) for its possible use in the sequestration of Congo red (CR) and methylene blue (MB) from industrial wastewaters. Qualitative analysis presented the adsorbent as a material of porous surface, containing –OH and –C = O functional groups that are known active sites. The material experienced three main thermal decomposition stages. It’s surface area, micropore volume and pore diameter were estimated as 194.725 m²g^–1, 0.173 cm³g^–1 and 3.00 nm, respectively. OPCA was very efficient in the sequestration of CR and MB. Its best performance was obtained at pH 2 for the sorption of CR, and pH 6 for the sorption of MB. Optimum dye removal was obtained after 180 min and 120 min for the sorption of CR and MB, respectively. Dye sequestration was favored by increasing dye concentration, as well as temperature. At the chosen experimental condition, about 300 mg and 100 mg adsorbent almost completely removed CR and MB, respectively. Experimental data best fitted the pseudo-second order kinetic model with R² of 0.9894 and 0.9991 for the sorption of CR and MB, respectively; while the Langmuir isotherm best described the equilibrium data. The calculated mean-free-energy, E, was < 8 k Jmol^–1 for the sorption of both dyes, thereby predicting physisorption. The standard enthalpy, ΔH°, of the process was respectively calculated as 23.69 kJ mol^–1 and 18.58 kJ mol^–1 for CR and MB removal. The ΔH° values suggest weak chemisorption and physisorption for the sorption of CR and MB, respectively.