Study On The Preparation, Characterization And Functionality Of Chitosan Resins For Water Treatment

In aquaculture, only 20% feed were used by aquaculture organisms. The residual feed and the excrement of aquaculture organisms remained in aquaculture water. So the aquaculture water is rich in nitrogen and phosphorus. The higher contents of nitrogen and phosphorus can cause water eutrophication and lead to the excessive growth of algae. Algae consume the dissolved oxygen in water, which can lead to the mass mortality of aquaculture organisms for hypoxia. Some toxic algae can secrete toxins which can transport through food chain to human body, and raise the food safety issues.Therefore, the objectives of this study are to treat the problems in aquaculture water, such as the higher contents of nitrogen and phosphorus, the excessive growth of algae. In this study, a series of chitosan resins are prepared to treat the aquaculture water.1) The shortcomings of chitosan resin, small pores, brittle and small particle size, limit its industrial applications. As pore-foaming agent, PEG 2000 can increase the amount of pores inside chitosan resin significantly. Chitosan-PVA blend resin (CPR), is prepared by IPN blend method. CPR has high mechanical strength. The best preparation condition is that the ratio of chitosan and PVA is 5:2, the dosage of glutaraldehyde is 10 ml/100 ml, and the dosage of PEG 2000 is 1.2%. FTIR indicates that it form the typical IPN structure between chitosan and PVA. In addition, chitosan can form larger particle size through blending with other adsorbents. Take diatomite for example, when the ratio of chitosan, PVA and diatomite is 5:2:2, the particle size increased obviously, the particle size larger than 40 mash account for 88.82% of the total chitosan resin.2) The nitrogen in aquaculture water is mainly originated from protein. To improve the adsorption ability of chitosan resin for protein, chitosan immobilized tannins resin (TICR) and chitosan-Ce⁴⁺ immobilized tannins resin (TCCR) were prepared by Mannich reaction and activation coupling reaction, respectively. The influences of several parameters (time, BSA initial concentration, pH and temperature) on the adsorption of TICR and TCCR were investigated. The results show that the adsorption capabilities increase with the increasing of time, and the adsorption equilibrium were achieved after 300 min. And the adsorption capabilities increase with the increasing of BSA initial concentration until the adsorption saturation achieve. The higher temperature is advantageous to the adsorption.The adsorption process of TICR for BSA is an endothermic process, and basically follows the Langmuir equation. The adsorption kinetics is satisfied with second-order equation. The adsorption mass transfer process is influenced and controlled by the liquid film diffusion and intraparticle diffusion. The process is mainly controlled by the intraparticle diffusion.3) Chitosan-La(â…¢)- phosphate ions imprinted resin (CLPR) were prepared by ion-imprinted method. The average particle size of CLPR is 300μm. The influences of time, temperature, initial concentration and pH were investigated. The results show that the adsorption capabilities increase with the increasing of time, and the adsorption equilibrium were achieved after 60 min. And the adsorption capabilities increase with the increasing of BSA initial concentration until the adsorption saturation achieve. And the influence of temperature is not obviously.The adsorption process of CLPR for phosphate follows the Langmuir and Frendlich equation. The adsorption kinetics is satisfied with second-order equation. The adsorption mass transfer process is influenced and controlled by the liquid film diffusion and intraparticle diffusion. Using KOH as desorption agent, CLPR can repeat adsorption–desorption cycle seven times.4) Chitosan-Re-bentonite resin (CRB) was prepared to inhibit Heterosigma akashiwo. With the treatment of low concentration of CRB (0.1,0.3 g/L), the amount of soluble carbohydrate increased with the increasing of treatment time. The reason is that when Heterosigma akashiwo cells are under stress, the cells show the emergency response to keep the normal cell physiological function. So the soluble carbohydrate contents increase. Under the high concentration of CRB stress, the cells are damaged. So the soluble carbohydrate contents decrease. The change trend of protein is similar to the soluble carbohydrate.With the same concentration of CRB, the MDA content of Heterosigma akashiwo cells increases with the increasing of treatment time. With the same treatment time, the MDA content increases with the increasing of CRB concentration. The effects of CRB on the antioxidant system of Heterosigma akashiwo cells are also investigated. The results show that in the initial stage SOD, POD and CAT activities are increased to protect cells, but with the increasing of treatment time and CRB concentration, the cells were damaged seriously, SOD, POD and CAT can not protect the cells.The effect of CRB on Chlorella Vulgaris is similar to Heterosigma akashiwo. With the treatment of 0.1 g/L CRB, the number of cells only remains 16%.