Alkali Lignin from Rice (Oryza sativa L.) Husk as Adsorbent for Aqueous Methyl Orange and Bromothymol Blue: Analysis of the Adsorption Kinetics and Mechanism

In this study, lignin was isolated from rice (Oryza sativa L.) husk using alkaline extraction method and used as an adsorbent for aqueous solutions of methyl orange (MO) bromothymol blue (BTB). The equilibrium removal rate MO found to be at 61.4%, with experimental adsorbate uptake, qe, 1.23 mg·g-1, achieved 150 minutes contact time. For BTB, the 78.3%, qe 1.57 Pseudo-first order (PFO) pseudo-second (PSO) kinetic models were then investigate kinetics adsorption process. Both BTB on follow a PSO model, rates 6.84 x 10-3 g·mg-1·min-1 0.69 g·mg-1·min-1, respectively. Langmuir, Freundlich, Dubinin-Radushkevich (DR), Brunauer-Emmett-Teller (BET), Flory Huggins (FH), Temkin isotherm determine appropriate model both substrates. Based calculations performed, best described adsorptive BTB. processes occur spontaneously, constants 0.083 L·mg-1 0.012 L·mg-1, respectively.