Evaluation of the Efficiency of a Chitosan Membrane in Removing Gallic Acid from Wastewater Using Adsorption in Batch Mode and Separation by Dead-End Filtration

This study assesses the efficacy of adsorption and separation techniques for removing gallic acid (GA) from wastewater using a chitosan membrane (Chi -1.5%). The effect of GA concentration, mass of adsorbent, contact time and pH were investigated. GA adsorption was best fitted by the Freundlich and Langmuir isotherm models, with a correlation coefficient of 0.9972 and 0.9929, respectively. The maximum adsorption capacity of GA (301.70 mg/g) was calculated at pH 8.4 and 303 K. Gibbs free energy was also calculated. The negative value showed that the GA adsorption is spontaneous. On the other hand, the value of activation energy of adsorption (< 7 kJ/mol) indicates that the adsorption is physical in nature. The adsorption kinetics was best fitted by the pseudosecond -order model, and the effect of pH (8.4 and 7.1) on the adsorption is explained by theoretical calculation of the fraction of ions present in solution and their affinity for the membrane. The maximum percentage of GA removal based on a dead-end filtration system was 18.58% at a GA concentration of 300 ppm, pH 8.4 and a pressure of 1 bar. Volume exclusion was found to have a very slight effect on removing GA from the aqueous phase, while adsorption played the main role in removing GA.