Removal of Congo Red Dye Using an Adsorbent Prepared from Martynia annua, L. Seeds

Activated carbons M1 and M2 were prepared from the seeds of Martynia annua, L. using H2SO4 and H3PO4 as chemical activating agents respectively. In this study, utilization of these adsorbents for the removal of Congo red (CR) dye from aqueous solution was investigated. The physical, chemical and morphological properties were determined using XRD, BET and SEM techniques. Experiments of CR adsorption on the prepared adsorbents were conducted using batch technique and their results were also compared. The data were tested with five different isotherm models; it fitted to Langmuir isotherm for M1 and for M2, four of the isotherm models fit with high correlation coefficient. Maximum adsorption capacity (mg/g) obtained for M1 was 12.45 and 29.85 for M2. Pseudo-second-order kinetics explained the adsorption process much better with good correlation coefficient. The adsorption rate was film diffusion controlled during the initial stages, and in the later stages the rate was controlled by intra particle diffusion. Increasing the temperature of the system decreases the equilibrium time accompanied by exothermic removal of CR. These studies indicate that the prepared adsorbent showed good adsorption characteristics towards textile dyes.