Abstract
In this work, the potential application of TiO2-Fe-HNT photocatalyst-adsorbent composite in water treatment technologies was confirmed. The photocatalyst-adsorbent composite (TiO2-Fe-HNTs) was synthesized by the hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. The adsorption and photocatalysis mechanism by the TiO2-Fe-HNT composite were examined on methylene blue dye, rhodamine blue dye, naproxen sodium (pharmaceutical drug waste), and imidacloprid (pesticide). The TiO2-Fe-HNT composite was active in UV and visible regions of the electromagnetic spectrum. The adsorption and photocatalytic efficiency increased with increasing amount of HNTs. The photocatalyst-adsorbent composite exhibited excellent removal efficiency for pharmaceutical waste (naproxen sodium) and pesticides (imidacloprid). An adsorption equilibrium data fitted well with the pseudo-second-order kinetics for both methylene blue and rhodamine blue dyes with the intraparticle model describing its rate-controlling steps. The Langmuir and Freundlich isotherm models further described the adsorption of methylene blue and rhodamine blue molecules, respectively.
Highlights
One of the major problems faced by humanity all over the world is poor water quality
A calculated amount of Halloysite nanotubes (HNTs) was added to 20 mL of isopropyl alcohol (IPA) and sonicated for 90 minutes. e dispersed HNTs in IPA were added to Solution C and agitated continuously for another 90 minutes. e resulting solution was transferred into an autoclave and heat treated at 180°C for 3 hours
A total of 16.6 wt.% loss was recorded for HNTs. e TGA curve for the composite TiO2-Fe-HNTs was a combination of the curves of HNTs and TiO2. e total weight loss recorded over the entire temperature at which the heat treatment was carried out was ca. 12.5%
Summary
One of the major problems faced by humanity all over the world is poor water quality. E increase in human population with its associated increase in industrialization and climate change is expected to result in an increase in demand for safe water [2]. E number of people not having access to safe water is expected to grow due to increased water contamination from industrial and human activities. Water pollution has associated economic and social impact such as increase in expenditure on health, long risky journeys to collect portable water, and poor school attendance due to ill health. To render water bodies safe for use, these pollutants must be removed, and different water treatment technologies have been developed to reduce the worsening of clean water shortage and meet the increased demand for potable water [10]. E different water treatment technologies can be categorized into three: tertiary, secondary, and primary [11]. Oxidation and advanced oxidation processes, adsorption, distillation, and solvent extraction can be categorized under tertiary treatment technologies [3, 11]. e right method to be adopted during water treatment is dependent on the extent of pollution and the nature of the pollutant
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