Study On Adsorption Efficiency Of Congo Red By Zinc Oxide Modified Sludge Biochar

Azo dye is a common pollutant at present,which has great harm to human body and the environment.Congo red is a typical azo dye,while sludge is a common by-product of waste water treatment,and its disposal has always been a relatively difficult problem.In this paper,combined with the current hot research,the sludge was fired into biochar and modified with zinc oxide to obtain the best modified sludge biochar.Determined by adsorption kinetics and adsorption isotherm,modified sludge biochar is optimal proportion of firing temperature and modification,modification of carbon on the equilibrium adsorption from the Congo red was 113.40 mg/g,its adsorption behavior in line with the false secondary dynamics,adsorption isotherm of Langmuir adsorption,adsorption saturation of modified carbon stripping and metal dissolution studies have shown that balance stripping quantity is 30.32 mg/g,metal dissolution amount is about 0.2%.Through the study of temperature influence and the analysis of thermodynamic equation,it is found that the modified sludge biochar is a spontaneous endothermic process,which is dominated by chemical adsorption and accompanied by physical adsorption.Through the p H effect study and the zero electric point analysis of the modified carbon,it is speculated that the dominant mechanism of adsorption is electrostatic adsorption.Further analysis of the influence of the co-existing anions in the solution revealed that the co-existing anions would compete with Congo red at the active sites indicated by biochar and inhibit the adsorption of Congo red.Moreover,the smaller the hydration radius of the ions,the greater the influence on the adsorption process.The analysis of the influencing factors and the characterization of the properties of the modified sludge biochar showed that the adsorption of Congo red on the surface of the modified carbon was mainly electrostatic adsorption,that is,the positive charge on the surface of the modified carbon was caused by the mutual attraction of anions after the hydrolysis of Congo red.This study provides a basis for the application of sludge biochar modification and adsorption treatment of Congo red wastewater.