Fabrication of chitosan/titanium dioxide composites film for the photocatalytic degradation of dye

The investigation of the chitosan film as a polymer matrix for titanium dioxide (TiO2) dispersion was carried out. Chitosan-titanium dioxide composite films were prepared by solution casting, using Chitosan, TiO2, Arquad T50 HFP as surfactant. The mixture of 1.0 g chitosan in 100 mL acetic acid was prepared, subsequently with the addition of TiO2. The solution was then cast onto an acrylic mold and allowed to air-dry. The external morphology of the composite film revealed the high dispersion of TiO2 in the polymer matrix. Three types of crosslinking agent; glutaraldehyde, citric acid, and itaconic acid were studied. It was found that chitosan film crosslinked with 1.12 mM citric acid for 5 min exhibited the highest tensile strength about 150.4 MPa. X-ray diffraction patterns of the dried film revealed the minor change in the theta of the crystalline region of chitosan. The diffraction line shift was likely due to the change in its chain orientation caused by the covalent interactions between chitosan and the crosslinking agent. The non-crosslinked chitosan-TiO2 composite film exhibited the higher tensile stress at maximum load with TiO2 content of 1 wt%, whereas the high content of TiO2 revealed the poor tensile stress at maximum load due to an aggregation of nanoparticles. The spent film for dye removal had the lower tensile stress at maximum load than that of the original film. Three reactive dyes of RR 120, RY 17, and RB 220 were selected as a representative contaminant. The optimal TiO2 amount for dye removal in both UV and dark conditions was 1 wt.% of chitosan. The chitosan-TiO2 composite films without crosslinking had the higher efficiency in dye removal than the crosslinked films. Dye removal in UV condition had the higher efficiency than without UV for all initial dyes concentrations in the range of 10 to 100 mg. L-1. The ratio of sorption to photocatalysis of RR120, RY17, and RB220 were 70.7:29.3, 78.5:21.5, and 92.2:7.8, respectively. Langmuir isotherm was used for data analysis for dark condition and the results showed that q(max) of RR120, RY17, and RB220 were 46.8, 427.1, and 229.1 mg-dye. g(-1)-chitosan-TiO2 film, respectively. The analysis of dye removal in UV condition followed satisfactorilly a Langmuir-Hinshelwood model in dye removal efficiencies. This indicated that photocatalysis process occurred on the surface of TiO2 and in the solution.