Low-cost halloysite-fly ash composite for the removal of pharmaceuticals, dyes and surfactants from contaminated water.

Abstract

Environmental contamination by dyes, pharmaceuticals, and surfactants is a global concern, highlighting the urgent need for effective removal methods. We investigated a low-cost composite based on halloysite (HAL) and fly ash (FA) as a adsorbent for removal of surfactant: sodium dodecylbenzenesulfonate (SDBS); dyes: Remazol brilliant blue r (RBBR), Rhodamine b (RB); pharmaceuticals: sulfamethoxazole (STX), ibuprofen (IB) from single adsorbate solutions and real wastewater. The dualistic approach was employed: advanced instrumental analysis for adsorbent-sorbate interactions study and sorption experiments conditions (effect of initial organic compounds concentration, the solution pH) for sorption efficiency assessment. The characterization of adsorbents included X-ray diffraction, X-ray fluorescence and X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy. The composite with a 20:80 ratio of HAL to FA exhibited the best sorption properties. The sorption capacity for RBBR, RB exceeded 20 mg/g and 4 mg/g, respectively, while for IB, STX and SDBS the sorption capacities were above 0.9, 0.3, and 8.5 mg/g, respectively. In general, slightly acidic conditions (pH 5-7) promoted RBBR, RB and STX adsorption; alkaline conditions (pH > 9) promoted IB adsorption. The X-ray photoelectron spectroscopy revealed a complex physical adsorption process involving dispersion forces, hydrogen and electrostatic bonding. The studies showed that the eco-friendly and inexpensive composite can simultaneously uptake organic compounds from wastewater. Although the competition effect of inorganic/organic molecules affected the sorption efficiency, the removal of SDBS from wastewater reached 100 %. Further research will focus on investigating granulated composites in dynamic column systems to advance purification technologies.