Application of chitosan composites for the removal of organic dyes

Tan, Jia Hui (2021) Application of chitosan composites for the removal of organic dyes. Final Year Project, UTAR.

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Abstract

Recently, chitosan has received particular attention from researchers to be used as a potential biosorbent for the removal of organic dyes. It is a biodegradable, inexpensive and renewable biopolymer derived from food waste. It consists of carboxyl (–COOH), hydroxyl (–OH), amine (–NH2) and amide (–NHCOCH3) functional groups on its surface that are responsible to remove organic dyes. However, pure chitosan has some limitations that exhibit lower biosorption capacity, surface area and thermal stability than chitosan composites. Many research studies have been carried out to improve the physicochemical properties of pure chitosan by modifying it with the addition of reinforcement materials to synthesise chitosan composites. Therefore, this study incorporates multiple journals to reveal the performance of various chitosan composites synthesised by other researchers to remove organic dyes. The reinforcement materials used for the synthesis of chitosan composites were classified as carbon-based materials, metal oxide and other biopolymer. Tripolyphosphate and epichlorohydrin were the two commonly used crosslinking agents to combine pure chitosan with the reinforcement materials. This study was conducted in five steps: i) review planning; ii) the searching process of basic literature; iii) publication screening and selection; iv) data extraction; v) data analysis and report writing. The physicochemical properties of chitosan composites were studied through scanning electron microscopy (SEM), energy dispersive X-ray (EDX), surface area analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric (TGA). The characterisation results revealed that the chitosan composites possessed a heterogeneous surface with a larger surface area (> 1.81 m2 /g) and became more amorphous than pure chitosan (> 0.141 m2 /g). The chitosan composites also had a higher thermal stability with less than 40 % weight loss at each stage of the thermal degradation process. Besides, the FTIR results showed that the presence of additional functional groups on the chitosan surface could facilitate the interaction with dye molecules and improve the biosorption capacity. Therefore, chitosan composites exhibited better physicochemical properties than pure chitosan. Lastly, the behaviour of the biosorption process for various chitosan composites was compared and analysed through the kinetic models, isotherm models and thermodynamic parameters. The findings with a high coefficient of determination (R 2 ) value suggested that most of the biosorption processes were better defined by the pseudo-second-order (PSO) kinetic model and Langmuir isotherm model. This indicated that monolayer chemisorption of organic dyes occurred on the homogenous surface of chitosan composites. Based on the biosorption thermodynamic results, most of the biosorption processes were endothermic, feasible, spontaneous at the low temperature range between 288 K and 320 K. Therefore, chitosan composites have been proved as a promising biosorbent for the removal of organic dyes.

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