WASTE BAOBAB AND TAMARIND LEAVES OF DHOFAR AS ADSORBENTS FOR PROPIONIC ACID REMOVAL FROM ITS AQUEOUS SOLUTION: ADSORPTION KINETIC MODELLING

Abstract

The adsorption kinetics of propionic acid from its aqueous solution onto raw and activated baobab (RB, AB) and tamarind (RT, AT) biosorbents of Dhofar were systematically investigated to evaluate the influence of biosorbent activation on adsorption performance and mechanism. Experimental data were analyzed using linear forms of five kinetic models, including pseudo-first order (PFO), pseudo-second order (PSO), Elovich (EV), intra-particle diffusion (IPD), and Boyd (BY) models. Model performance was assessed through comprehensive error analytical parameters, including sum of squared errors (SSE), mean squared sum of errors (MSSE), standard error (SE), average absolute relative deviation (AARD), and determination coefficient (R2). The results revealed that adsorption capacity and rate were significantly enhanced after chemical activation, with AB showing the highest overall performance followed by RB, AT, and RT. Kinetic analysis indicated that the pseudo-second-order model best described the adsorption process for all biosorbents, supported by the highest R² values and the lowest error statistics, suggesting that chemisorption is the dominant mechanism controlling propionic acid uptake. The Elovich model further confirmed adsorption on heterogeneous surfaces, while IPD and Boyd models indicated that both film diffusion and intraparticle diffusion contributed to the overall rate, without being sole rate-limiting steps. Error analysis validated the robustness and reliability of the PSO model in predicting adsorption behavior. Overall, the study demonstrates that waste-derived baobab and tamarind biosorbents, particularly in activated form, are effective, low-cost, and sustainable materials for propionic acid removal from aqueous solutions, offering promising applications in wastewater treatment.