Removal of Nonylphenols From Water and Wastewater Using Alginate-Activated Carbon Beads

The presence of contaminants of emerging concern (CECs) have been affecting water quality in recent years. The United States Environmental Protection Agency (U.S EPA) defines CECs as toxic chemicals without regulatory status and with adversely impact on the wildlife and people. Among the CECs, nonylphenols (NPs) are frequently found in all water systems and are categorized as endocrine-disrupting compounds (EDCs) due to their ability to mimic hormones causing reproductive and developmental effects in humans and animals. The main sources of discharge and distribution of NPs into the environment are wastewater treatment plants (WWTPs) which are not designed to remove them. Therefore, it is needed to develop methods that can effectively remove NPs from wastewater. This study proposed the use of ecofriendly adsorbents made from alginate and activated carbon (Alg-C beads) aiming to remove NPs from water and wastewater. The removal efficiency of Alg-C beads was tested under various conditions including dose, pH, and temperature. The potential for reusability was also evaluated. The potential sorption mechanism and thermodynamics of NPs sorption by Alg-C beads was also studied. A solventless extraction technique, called stir bar sorptive extraction (SBSE) was used for NPs analysis by thermal desorption gas chromatography with mass spectroscopy (TD-GC-MS). The results showed the ability of Alg-C beads to successfully remove 97% NPs from aqueous solutions in DI water and wastewater within 90 minutes under static conditions. The adsorption capacity for Alg-C beads ranged from 0.389 – 0.103 mg/g, where the sorption model fitted a pseudo second order and Freundlich model (R2=0.861). These findings suggests that the surface of Alg-C beads is heterogenous and the sorption mechanisms appeared to be influenced by a physical process. Furthermore, the Alg-C beads exhibit both exothermic (−ΔH°) and endothermic ( ΔH°) properties at different dosages, leading to inconclusive results. The removal efficiency of Alg-C beads was not affected by the pH in the water. In this study, Alg-C beads consistently delivering optimal performance in removing NPs for up to five cycles; a testament to their reusability and recyclability. When tested with wastewater, the removal efficiency of the Alg-C beads was found to be 97% and the matrix effect remained unaffected. Thus, the results from this study have demonstrated the potential application of Alg-C beads for the removal of NPs from water and wastewater samples