Abstract
Natural organic matter (NOM) is ubiquitous in aquatic environments and has recently become an issue of worldwide concern in drinking water treatment. The major component of NOM is humic acids (HA). In this study, a natural zeolite (mordenite) was modified employing hexadecyltrimethylammonium bromide (HDTMA) to enhance greater efficient sites for sorption of HA. The natural zeolite and surfactant-modified zeolite (SMZ) were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FT-IR), N2 Adsorption–desorption isotherms and BET-specific surface area, thermographic analysis, derivative thermographic analysis (TGA-DTA) and Field emission scanning electron microscopy (FESEM). A fixed-bed reactor was used for the removal of HA and the effects of different experimental parameters such as HDTMA loading levels, HA solution flow rate, solution pH and eluent concentration were investigated. The results indicated that the SMZ bed with HDTMA loading of 75% of external cation exchange capacity (ECEC) at a flow rate of 2 BV/h and pH of 10 showed the greatest enhanced removal efficiency of HA while ethanol solutions (25%v/v) with feed flow rate of 2 BV/h were sufficient for complete regeneration of SMZ and desorption of HA. Measurements of surface area of SMZ indicated that a monolayer formation of the surfactant at those conditions allowed the optimum removal of HA.
Highlights
Natural organic matter (NOM) which is ubiquitous in aquatic environments, ground and soil waters, has recently become an issue of worldwide concern in drinking water treatment (Rao et al 2011)
The results indicated that the surfactant-modified zeolite (SMZ) bed with hexadecyltrimethylammonium bromide (HDTMA) loading of 75% of external cation exchange capacity (ECEC) at a flow rate of 2 bed volumes (BV)/h and pH of 10 showed the greatest enhanced removal efficiency of humic acids (HA) while ethanol solutions (25%v/v) with feed flow rate of 2 BV/h were sufficient for complete regeneration of SMZ and desorption of HA
The surface of natural zeolite was modified with HDTMA to enhance its HA adsorption capability
Summary
Natural organic matter (NOM) which is ubiquitous in aquatic environments, ground and soil waters, has recently become an issue of worldwide concern in drinking water treatment (Rao et al 2011). Since the early 1970s, water quality and treatment issues related to NOM have been reported, where these substances in natural water facilitated bacteria reproduction during drinking water distribution and produced harmful disinfection by-products (DBP), such as trihalomethanes (THMs), during chlorination process. They caused a reduction in the effectiveness of water purification by interfering with various oxidants, increasing the solubility of heavy metals due to complexation with metals and adsorbed organic pollutants (Yang et al 2007). They are classified as potentially carcinogenic chlorine organic compounds (Lee et al 2009)
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