Adsorption of methylene blue onto powdered activated carbon immobilized in a carboxymethyl sago pulp hydrogel

The potential of crosslinked carboxymethyl sago pulp (CMSP) beads immobilized with powdered activated carbon (PAC) as an adsorbent for methylene blue (MB) adsorption was investigated. The finely powdered PAC had an excellent adsorption capacity for MB but was disadvantageous for the separation process from treated effluents. To ease the separation process, the CMSP medium could be advantageous for the process by acting an immobilizing medium for PAC. The MB adsorption reached equilibrium at the 14th hour, and further adsorption was studied to determine the effects of the CMSP concentration, PAC dosage, and pH. Different CMSP concentrations in the preparation of CMSP–PAC beads showed no significant differences; this proved that CMSP–PAC adsorbed more MB than CMSP did. The MB adsorption increased with increasing PAC concentration, whereas the CMSP–PAC beads disintegrated at pH 11.5. In the equilibrium study, the Langmuir isotherm fit well into the experimental data with a linear correlation coefficient (R²) of 0.9837 and a maximum adsorption capacity of 250 mg/g. The kinetic study showed that pseudo-second-order kinetics accommodated the experimental data well with an R² value of 0.9512 and a pseudo-second-order rate constant value of 3.61 × 10⁻³ min⁻¹. The crosslinked CMSP–PAC beads have the potential to remove MB dye, and this could be exploited as an alternative to treating colored dye effluents produced by industries such as the textile, printing, and cosmetics industries.