Chemosynthesis Of Chitosan Carrier Algicide Containing Copper And Its Application

Cupric sulfate anhydrous is widely used as an effective algicide both at home and abroad as eutrophication is getting more and more serious all over the world currently while partially high concentration of Cu²⁺ caused by direct usage of CuSO₄ can do harm to aquatic organisms and finally deteriorate water bodies. For this reason, carrier algicide which can release Cu²⁺ gradually is becoming the study focus in this field. Chitosan (CTS) is a kind of natural macromolecular compound which contains -NH₂ and -OH and is the ideal carrier because it possesses excellent adsorption characteristics and is easy to be degraded.In this article; CTS was chosen as the carrier and CTS carrier algicide containing copper was synthesized on the basis of study on its adsorption and desorption of Cu²⁺ while Chlorella pyrenoidosa was selected to test performance of the algicide.Effect factors on adsorption capacity of Cu²⁺ by CTS were discussed applying single factorial experiment. The results were shown as follows: adsorption capacity ascended with the increase of initial [Cu²⁺] and the biggest capacity was obtained when [Cu²⁺] reached 1200mg/L while it descended with the increase of CTS dosage and got the biggest one when dosage decreased to 0.025g; though adsorption capacity ascended with the increase of pH, 4.5 was the right pH value in consideration of all respects; with the rise of temperature adsorption capacity went upward initially but tended downward soon after and the turning point is 40℃;adsorption capacity ascended with time extending and got the biggest one at approximately 90min.Results from orthogonal experiment of Cu²⁺ adsorption by CTS showing the order of priority for each factor were as follows: CTS dosage > temperature > initial [Cu²⁺] >adsorption time. In this experiment, optimal combination for Cu²⁺ adsorption by CTS could be obtainned when CTS dosage was 0.025g , temperature was 40℃, adsorption time was 60 min and initial [Cu²⁺] was 1200mg/L.The quantity of Cu²⁺ released from CTS- Cu²⁺ increased with time extending and the release rate was very fast in initial 24h which can be described as linear increase while it slow down apparently with scalariform increase of Cu²⁺ . The release kinetics of Cu²⁺ from CTS- Cu²⁺ conformed to Elovich equation, Langmuir equation as well as second dynamic equation. With the raise of pH the quantity of Cu²⁺ released from CTS- Cu²⁺ decreased, but the influence was not evident when pH varied from 6 to 8 while it increased with raise of CTS- Cu²⁺ dosage and 0.69mg/L of [Cu²⁺] could be obtained when the dosage was 50mg/L and release time was more than 24h which could guarantee removal efficiency of algae theoretically.The maximal adsorption wavelength for Chlorella pyrenoidosa was 680nm and Chlorella pyrenoidosa's whole vegetative cycle lasted 8d with variation of pH from 6.14 to 7.67.The lag phase, logarithm phase, stationary phase and decline phase appeared at the first day, the second day, the seventh day and the eighth day respectively.As for Chlorella pyrenoidosa, the optimal time of algicide application was in lag phase. CTS- Cu²⁺ algicide could restrain the growth of algae through releasing Cu²⁺ gradually with change of pH of algae solution and the more the dosage of algicide the better the removal efficiency of algae. For original algae solution, effective dosage of algicide was 200mg/L. As for stimulant eutrophication water body, 96h—EC₅₀ of Chlorella pyrenoidosa CTS- Cu²⁺ algicide was 12.8mg/L and algae growth could be effectively restrained with algicide dosage of 20mg/L while residual [Cu²⁺] was 0.38mg/L which is less than limit of [Cu²⁺] in Standards for drinking water quality and would neither do harm to fishery nor deteriorate aquatic eco-environment.Limited by testing condition and time, removal efficiency of algae by CTS- Cu²⁺ algicide in real eutrophication water sample was not tested and toxicology towards fish was not carried on as well as influence of algae removal efficiency by flocculation was in need of further study.