The investigation of humic acid adsorption from aqueous solutions onto modified pumice with hexadecyl trimethyl ammonium bromide

Aims: This study was conducted to evaluation humic acid adsorption from aqueous solution using pumice modified with cationic surfactant. Materials and Methods: The pumice modification was carried out with cationic surfactant of hexadecyl trimethyl ammonium bromide (HDTMA-Br) with a concentration of 3 mmol/l for 48 h using a 150 rpm shaker. The chemical structure of pumice was determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD). For evaluation of the effective parameters, the adsorption of humic acid onto modified pumice was conducted with batch experiments. Humic acid concentration was determined by photometry on 254 nm. Langmuir, Freundlich, and Temkin models and pseudo-first and pseudo-second-order kinetics were used for adsorption isotherm and kinetics studies. Results: The results showed that humic acid adsorption increased as its initial concentration, the adsorbent dosage, and the contact time increased. Increase in pH within the regions 3-12 resulted in the reduction of adsorption efficiency while the optimum adsorption occurred at pH = 3. The adsorption data followed the Langmuir model (R² = 0.99) and second-order kinetic model (R² = 0.99). Maximum experimental adsorption and theoretical adsorption capacity of the adsorbent were 22.5 and 29 mg/g, respectively. The Langmuir constant coefficient (b) was determined as 0.8 L/mg. Conclusions: It was understood from the results of this study that adsorption onto modified pumice is efficient in performance and thus affordable technology for the elimination of humic acid from the polluted water supply.