Kinetic Parameters and Mechanism of Zn (II) Adsorption on Lignite and Coconut Shell–Based Activated Carbon Fiber

The adsorption of Zn (II) on lignite and coconut shell–based activated carbon fiber (ACF) was studied using a batch process to determine the governing mechanism of Zn (II) removal and the most suitable kinetic model. Zn (II) adsorption was found to be enhanced at higher solution temperatures, and the optimal contact time for Zn (II) adsorption on ACF was found to be 50 min. The pseudo-second-order kinetic model (Type 1) proved to be the most applicable, followed by the Elovich model, suggesting that chemisorption is the rate-limiting step based on the highest coefficient of determination, R2, and the lowest normalized standard deviation, Δqt(%). The calculated qe(cal.) values derived from kinetic equations were compared to the experimental qe(exp.) values, and the activation energy (Ea) was determined from an Arrhenius plot. The proposed adsorption mechanism based on intraparticle diffusion model suggested a multistep adsorption process for the Zn (II)–ACF system.