Preparation Of Chitosan - Based Photosensitive Micro - Nanoparticles And Treatment Of Arsenic In Water

Arsenic contamination is a global phenomenon, especially in the arsenic heavily polluted areas, the water has brought a variety of irreparable harm to humans and the environment, therefore the purification treatment of arsenic in water has attracted much attention. With the improvement of living standards, the removal standards of arsenic in water are becoming more stringent. Therefore the technology and materials for arsenic treatment are put forward higher requirements, such as high efficiency and environmental protection, etc.In this paper, chitosan which has biodegradable, environmental friendly, low cost and good adsorption separation function was selected as a material for loading, and the chitosan light sensitive magnetic nanoparticles (MTCNPs) were prepared by the reversed phase suspension crosslinking polymerization method with the photosensitive effect of Ti2 and which has the function of magnetic separation Fe3O4, the morphology, particle size and the adsorption efficiency of arsenic were studied. MTCNPs were characterized by using different techniques like Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Vibrating Sample Magnetometer (VSM) and Atomic Fluorescence Spectrometer (AFS). It was observed that the surface of MTCNPs were rough, the size was uniform and the shape was neat relatively, the best adsorption pH on As(Ⅲ) and As(Ⅴ) were 7.0,5.0, and the best adsorption temperature was 40℃, it could achieve higher adsorption efficiency within 0.5 h. The adsorption efficiency of MTCNPs on As(III) was 95% at NO3- and SO42- concentration range of 5-50 mg/L, however, it was reduced 35% at the presence of PO43-, but did not affect As(Ⅴ), at Ca2+、Mg2+ and Fe3+ concentration range of 50～600 mg/L, the adsorption of As(Ⅲ) and As(Ⅴ) were reduced 16.78%,14.38%、12.35% and 39.91%、 33.25%、38.46% respectively and for Fe3+concentration of 2-25 mg/L, the adsorption of As(Ⅲ) and As(Ⅴ) remained at 90%. It also could effectively increase 10%～20% adsorption efficiency for As(Ⅲ) when uv irradiation by MTCNPs. The process of As(Ⅲ) and As(Ⅴ) adsorption by MTCNPs fitted well to second order kinetics model. Isothermal adsorption study showed that the adsorption behavior of MTCNPs for arsenic followed the Langmuir model.Due to chitosan contains -NH2 and -OH groups, make it difficult to soluble in water, which limits its application. Quaternary ammonium salt of chitosan not only retains the structure of chitosan, but also has the characteristics of the cationic polymer, presumes to As(Ⅲ) has good adsorption. Chitosan quaternary ammonium salt was synthesized first, then quaternary ammonium salt of chitosan composite nanoparticles were prepared. Through the comprehensive analysis of the experimental results showed that the MTHCNPs-2 could be used under wide pH. Through contrat experiment, the adsorption efficiency of MTHCNPs-2 on As(III) was more than 95% at the presence of NO3- and SO42-, it was reduced 22% at the presence of PO43-, but almost did not affect As(V), at the presence of Ca2+、Mg2+ and Fe3+, the adsorption of As(Ⅲ) and As(Ⅴ) were reduced by 20.87%,14.13%,38.65% and 3.02%,2.78%、55.97% respectively, in low Fe3+ concentration of 2-25 mol/L, almost did not affect the adsorption efficiency of arsenic. The process of As(Ⅲ) and As(Ⅴ) adsorption by MTHCNPs-2 well described by second order kinetics model and Langmuir model, the maximum adsorption capacity for As(Ⅲ) and As(Ⅴ) were 33.864 mg/g and 34.614 mg/g at 313 k. After 10 adsorption-desorption cycles, adsorption efficiency was only reduced by 7.55%, showed that the material has good reusability.On the basis of the previous work, the dynamic analysis on the material for arsenic adsorption was also studied. Adsorption device was designed for fixed glass column upflow ion exchanger, filled with quaternary ammonium salt of chitosan composite nanoparticles (MTHCNPs-2) as adsorption material. The results indicated that the column adsorption efficiency of MTHCNPs-2 on As(Ⅲ) adsorption was very high, up to 660 BV, the low PO43-concentration of 5 mg/L did not impact adsorption of MTHCNPs-2, when the concentration was as high as 50 mg/L, the adsorption efficiency of the material was reduced by 35%, but the concentration of PO43- in groundwater is generally very low(≤0.2 mg/L), so the existence of PO43- will not affect the adsorption performance of materials. And when the concentration of Fe3+ was 25 mg/L, it almost also did not affect the adsorption properties. After desorption, the material still had good adsorption performance, reduced the cost for the treatment of arsenic contaminated water. Previous research found that the material was expected to be applied to small equipment and instruments, which was applied to the "point processing regulation scheme", for the purification of arsenic in water provided a simple and effective technique.