Adsorption of bromophenol blue and bromothymol blue dyes onto raw maize cob

Abstract

The adsorption of Bromophenol blue (BPB), and Bromothymol blue (BTB) onto raw maize cob from aqueous solution was studied using bach adsorption technique, in which the influence of contact time, dosage, concentration, temperature, and pH, were investigated as well as characterizing the adsorbent using Fourier Transform Infrared (FTIR) spectroscopy, surface morphology using scanning electron microscopy and pH of point of zero charge (pH_PZC Results showed that Bromophenol blue and Bromothymol blue removal reaches optimum percentage about 96.53 %, and 94.39 % with equilibrium time within 125 and 110 minutes respectively. For both dyes the removal efficiency was found to increase with increasing initial dye concentration from 10 mg/l to 100 mg/l, and adsorption efficiency were found to be high at lower pH. also, increase in the dosage of the adsorbent leads to increase in the adsorption process for BPB but shows decrease for BTB. The equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin, and Dubinnin-Ruduskevich (D-R). The results revealed that the experimental data fits Temkin isotherm with R² values of 0.957 and 0.971 for BPB and BTB respectively. Kinetic analyses were conducted using pseudo-first second-order models, elovich equation and the intra-particle diffusion model. The regression results in addition to q_e experimental and q_e calculated showed that the adsorption kinetics was more accurately represented by pseudo-second-order model. Values of activation parameters such as free energy changes (Δ), enthalpy change (Δ), and entropy change (Δ) were calculated using vant Hoff equation. All Δ values were negative indicating that the adsorption was feasible and spontaneous. The result indicated that raw maize cob can be used as adsorbent for the removal of the tested dyes

Keywords: Adsorbate, Adsorbent, Adsorption, Maize cob, % Removal