Adsorption of Phosphate by CPC and HDTMA-Modified-Zeolite
Modification of natural zeolite surface with cetylpyridinium chloride (CPC) and hexadecyl tri methyl ammonium bromide (HDTMA) to improve the zeolite ability for phosphate removal was investigated. Batch experiments were conducted to determine the surfactant sorption capacities, which were found to be 476.19 mmol/L and 192.31 mmol/L for CPC and HDTMA, respectively. The sorption follows a Langmuir isotherm model. From FTIR spectra, two intense bands around 2920 cm-1 and 2875 cm-1 connected to asymmetric and symmetric stretching vibration of C-CH2 absorption bands of amine chains. This indicates that the surfactants have been adsorbed. The surfactant-modified-zeolites (SMZ) were then prepared by adding the surfactants in amount equal to 50%, 100% and 200% of the ECEC of the zeolite in order to study the influence of difference surfactant surface configuration of SMZs on the sorption of phosphate. Batch adsorption experiment for phosphate removal using the SMZs showed significantly improved removal of phosphate compared to the unmodified zeolite. The adsorption capacity of phosphate on the CPC-modified-zeolite at CPC concentration equal to 50%, 100%, and 200% of ECEC were 22.9 mmol/kg, 45.2 mmol/kg, and 11.8 mmol/kg respectively, while on the unmodified-zeolite, the adsorption capacity was only 6.0 mmol/kg. The effectiveness of the modified natural zeolite for phosphate removal depends on contact time, SMZ loading, pH and initial contaminant concentrations.