Abstract
Titanium dioxide (TiO2) is described as an established material to remove pollutants from water. However, TiO2 is still not applied on a large scale due to issues concerning, for example, the form of use or low photocatalytic activity. We present an easily upscalable method to synthesize high active TiO2 nanoparticles on a polyethersulfone microfiltration membrane to remove pollutants in a continuous way. For this purpose, titanium(IV) isopropoxide was mixed with water and hydrochloric acid and treated up to 210 °C. After cooling, the membrane was simply dip-coated into the TiO2 nanoparticle dispersion. Standard characterization was undertaken (i.e., X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, water permeance, contact angle). Degradation of carbamazepine and methylene blue was executed. By increasing synthesis temperature crystallinity and photocatalytic activity elevates. Both ultrasound modification of nanoparticles and membrane pre-modification with carboxyl groups led to fine distribution of nanoparticles. The ultrasound-treated nanoparticles gave the highest photocatalytic activity in degrading carbamazepine and showed no decrease in degradation after nine times of repetition. The TiO2 nanoparticles were strongly bound to the membrane. Photocatalytic TiO2 nanoparticles with high activity were synthesized. The innovative method enables a fast and easy nanoparticle production, which could enable the use in large-scale water cleaning.
Highlights
The environment on earth is being more and more contaminated by anthropogenic pollutants [1,2].Especially in water numerous contaminants like pharmaceuticals, endocrine disruptors, personal care products, and many more can be found and have an impact on animals and humans [3,4,5].Due to the lack of elimination of these contaminants by conventional treatment technologies, other methods like advanced oxidation processes (AOPs) were considered [6]
Before dip-coating in the TiO2 nanoparticle suspension the membrane membrane was modified with polyacrylic acid (PAA) and electron beam in order to generate carboxyl groups (COOH)
The surface was evenly covered with non-agglomerated nanoparticles, which were strongly attached to the membrane
Summary
The environment on earth is being more and more contaminated by anthropogenic pollutants [1,2]. Binding TiO2 to a support (e.g., membrane [11,12,13,14]) decreases the overall surface area but the degradation of pollutants can be executed in one step. An additional positive effect when decreasing the size of nanoparticles is the shortening of the diffusion length for photogenerated electron-hole pairs (i.e., recombination is diminished) [16]. Using nanoparticles is an ideal combination of high surface area and low electron-hole pair recombination. We designed a simple synthesis method without using toxic chemicals at low temperatures to gain highly photocatalytic active TiO2 nanoparticles [14]. TiO2 -membrane system was characterized regarding scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle measurement, water permeance, and stability of the nanoparticle attachment to the polymer surface. The photocatalytic activity was investigated by degradation of methylene blue as well as carbamazepine in a batch reactor
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