Adsorption Of Heavy Metal Ions In Water By Algal Wastes

In recent years,with the continuous growth of social economy,industrial and agricultural development has developed rapidly,and more and more heavy metals have been discharged into the environment,causing serious environmental pollution.Heavy metal pollution has become one of the most important environmental problems due to its bioaccumulation,high damage and difficult handling.At present,common methods for removing heavy metal ions from sewage include adsorption method,membrane separation method,chemical precipitation method,ion exchange and electrochemical method.The adsorption method has the characteristics of low cost,easy access to raw materials,good adsorption effect,and the like,and is widely used.In this paper,seaweed chemical waste-kelp slag was used as adsorbent to study its adsorption performance on heavy metal ions in water.Through the combination of static adsorption reaction and dynamic adsorption reaction,it provided theoretical support for the large-scale use of kelp slag.In this study,a series of static adsorption experiments were designed to detect the factors affecting the adsorption of Cu²⁺and Cd²⁺by kelp slag.The adsorption kinetics and adsorption isotherm model were used to infer the adsorption process,determine the adsorption capacity and adsorption type of kelp slag,and design dynamic tests.The effects of influent flow rate and solution concentration on dynamic adsorption were investigated.The dynamic adsorption model was used to describe and predict the adsorption process.The main conclusions are as follows: The particle size of kelp slag has a great influence on the removal rate of Cu²⁺ in water samples,while the particle size has little effect on the adsorption of Cd²⁺by kelp slag.The adsorption time of kelp slag on Cu²⁺ and Cd²⁺ is different?60 min and 210 min?;the adsorption process of Cu²⁺and Cd²⁺ by kelp slag can be described by quasi-secondary kinetic model.The control steps in both adsorption processes are internal diffusion adsorption stage;kelp slag on Cu²⁺and Cd²⁺The adsorption process can be described by the Langmuir isotherm adsorption model.The saturated adsorption capacity of kelp slag for Cu²⁺ and Cd²⁺ is 208.33 mg/g and 70.92 mg/g,respectively,and the kelp slag is calculated according to the DR isothermal adsorption equation.The average freeenergy of Cu²⁺ and Cd²⁺ adsorption is 0.1443 k J/mol and 0.6652 k J/mol,respectively.It is concluded that both adsorptions are physical adsorption processes;In the dynamic reaction of kelp slag adsorbing Cu²⁺ and Cd²⁺,the inlet velocity and solution concentration will have an impact on the penetration time and removal rate.Specifically,the faster the inlet velocity is,the shorter the penetration time and the lower the removal rate will be.The higher the influent concentration,the shorter the penetration time and the lower the removal rate.The homas model and the Yoon-Nelson model can well describe and predict the dynamic adsorption process of kelp slag on Cu²⁺ and Cd²⁺.This study systematically studied the adsorption of kelp slag on Cu²⁺and Cd²⁺,and made a theoretical basis for the subsequent popularization and application.