Adsorption Of Cadmium By Chlorella In Water

In recent years,with the progress of society and the acceleration of industrialization process,human beings have discharged a large number of heavy metals into the water.Cadmium pollution is particularly serious,which not only pollutes the environment,but also seriously affects aquatic animals and plants and even human health.Heavy metals can migrate and transform in water environment,adsorption is one of the important transformation forms.As an important part of heavy metal adsorption in natural water,biofilm includes inorganic components such as metal oxides and organic components such as algae.In recent years,eutrophication is becoming more and more serious,which leads to the increase of the proportion of organic components in the water body.Moreover,the specific surface area of organic components is relatively large and the surface functional groups are rich.Therefore,algae widely existing in the biofilm are selected as the research object of natural water adsorption of heavy metals.Compared with other algae,Chlorella vulgaris not only has the typical structure and properties of most algae,but also has the advantages of rapid growth and easy to be obtained by artificial cultivation.Therefore,in this paper,we take the Chlorella vulgaris[FACHB-1298]as an example to study the adsorption rule and influencing factors of Cd²⁺in water.The results show that:The adsorption process of Chlorella vulgaris for Cd²⁺mainly includes three stages:fast adsorption reaction,slow adsorption reaction and adsorption desorption equilibrium reaction.The adsorption process basically conforms to the quasi first-order kinetic equation.The adsorption equilibrium time of Chlorella vulgaris with biomass concentration of 100 mg/L is 53.4 min at 25℃,p H=7.14 and initial concentration of Cd²⁺is 2 mg/L.In addition,Chlorella has a faster adsorption rate for Cd²⁺and K=0.144 min^-1 by fitting the pseudo first-order kinetic equation.The period of 0-20 min is a rapid adsorption reaction stage,and the total adsorption amount of Cd²⁺can reach more than 94%of the total adsorption amount at the adsorption equilibrium;20-50 min is the slow adsorption reaction stage,and 50 min later is the adsorption desorption equilibrium reaction stage.In the experiment of the effect of subculture on the adsorption of Cd²⁺by Chlorella vulgaris,the error analysis of biomass growth and adsorption capacity of Chlorella vulgaris was carried out.The results showed that the growth of Chlorella vulgaris was the same as that of Chlorella vulgaris,and its adsorption capacity did not decline.When the concentration of Chlorella is 20.5 m L/kg,the adsorption rate of Chlorella increased gradually and reached equilibrium with the increase of biomass concentration In the experiment of Cd²⁺adsorption capacity of Chlorella with extracellular polymer retention and Chlorella with extracellular polymer removed,Chlorella sp.with extracellular polymer removed was in the first 20 min.The results showed that the adsorption rate of Chlorella vulgaris was faster than that of Chlorella vulgaris,which was 0.59%of that of Chlorella vulgaris.The results showed that Chlorella with extracellular polymers adsorbed more Cd²⁺than those without extracellular polymers,and the total amount of Cd²⁺adsorbed by extracellular polymers accounted for 0.27%of the total adsorption amount.However,the concentration of Cd²⁺in Chlorella vulgaris increased after long-term exposure to high concentration of Cd²⁺for a long time,and the Chlorella with extracellular polymer removed had a more obvious upward trend than that with the retention of extracellular polymer.Therefore,extracellular polymer can also reduce the toxic effect of Cd²⁺on Chlorella to a certain extent...