Shorea dasyphylla sawdust for humic acid sorption

The efficacy of Shorea dasyphylla sawdust as an adsorbent for the removal of humic acid from aqueous solution was investigated as a function of pH value, agitation period, agitation rate, initial humic acid concentration and adsorbent dosage. The equilibrium nature of humic acid adsorption was described by the Langmuir, Freundlich and BET isotherms. The experimental adsorption data was best fitted to the Langmuir adsorption model, which gave adsorption capacity of 68.4 mg humic acid adsorbed per gram Shorea dasyphylla sawdust at pH 2.0 and initial humic acid concentration of 80 mgaEuro-L-1. Kinetic studies indicated that the sorption process followed the pseudo-second-order kinetic model. It was revealed that after three cycles of adsorption and desorption, Shorea dasyphylla sawdust retained its promising adsorption ability. With an initial amount of 73.5 mg humic acid adsorbed per gram sawdust, more than 80% of humic acid desorbed by using 0.1 M HCl. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to study the mechanism of the removal of humic acid. From the dimensionless factor, R-L data, it was determined that the adsorption of humic acid onto untreated Shorea dasyphylla sawdust was favourable.