Toxic Effect Of Cadmium In Water On Green Algae And Adsorption Efficiency Of Green Algae To Cadmium

With the rapid development of social economy in recent decades,environmental problems have attracted people's attention,especially in recent years,the central government has increased the intensity of environmental protection.Various methods of remediation of water pollution have been developed,and the use of algae and other bioremediation of water heavy metal pollution or the use of biosorbent treatment of sewage is a widely used technology.Chlorella and other green algae widely exist in water bodies,and grow rapidly.They are easy to carry out large-scale breeding,and have a certain adsorption capacity of heavy metals,which can effectively reduce the content of heavy metals.However,the toxic effects of heavy metals on living algae affect their normal growth and,to some extent,inhibit the application of algae in water treatment.At the same time,under heavy metals stress,toxic algal cells can reduce heavy metals through a series of physiological activities,which has important practical significance for the application of the activity of algae in the heavy metal in the water.In addition,the dead algae also have a certain adsorption capacity for heavy metals.In this study,the method of static experiment was used to study the toxicology of common green algae(Chlorella vulgaris and Scenedesmus obliquus)in water.The inhibitory concentrations of Cd(II)on the two algae were 5.94 mg/L and 4.13mg/L,respectively.At the same time,under different Cadmium Stress,the Chlorella and Scenedesmus' s chlorophyll a concentration;changes of extracellular soluble sugar and protein in cells were compared,and obtained two kinds of algae on Cd(II)tolerance,which showed better tolerance to cadmium in chlorella.In the adsorption experiment,the effects of different initial algal cell density,different initial heavy metal concentration,different acidity and alkalinity,and different temperature on the biosorption efficiency of live and killed Chlorella vulgaris were studied.The results showed that Chlorella had a good effect on cadmium And the adsorption efficiency of Chlorella vulgaris is higher than that of Chlorella.At the same time,the adsorption kinetics and thermodynamics of cadmium on chlorella were studied by batch balance method.The experimental data were analyzed by pseudo-first order kinetic equation,pseudo quadratic kinetic equation,Langmuir isotherm equation and Freundlich isotherm equation Together The results showed that the adsorption effect was the best under the condition of neutral acidity of solution,and the increase of temperature in a certain range was beneficial to the occurrence of adsorption.The biomass of algae and the initial concentration of cadmium all affected the adsorption effect to a certain extent.Pseudo-second-order kinetics equation,Langmuir isotherm equation and Freundlich isotherm equation can describe the process of adsorption from different aspects.The main functions of chlorella in this process are the functional groups such as C-O,C=O,-COOH and-NH-by infrared spectroscopy.