Study On Adsorption Of Vanadium And Arsenic By Pipe Scale In Water Supply Pipeline

As the lifeline of the city,the urban water supply pipe network plays an important role in conveying drinking water for residents,and it is of great significance to ensure its safe operation.At present,the safety of drinking water has been paid more and more attention,and the quality of drinking water cannot be guaranteed.The factors affecting the migration and transformation of heavy metal pollutants in drinking water and its mechanism are studied.On this basis,measures to maintain the stability of water quality in the pipeline network are actively explored.The secondary release of medium and heavy metal pollutants and the safety of drinking water have important theoretical and practical value.In this paper,through the adsorption experiments of heavy metal vanadium and arsenic-like on pipe scale,the changes of micro-characteristics,water quality,influencing factors,adsorption kinetics,isotherm and thermodynamics of pipe scale before and after adsorption were investigated,and the adsorption model of pipe scale for vanadium and arsenic was established by response surface methodology.The main conclusions are as follows:?1?The microscopic morphology of the tube scale before and after adsorption of vanadium or arsenic is needle-like.The needle-like structure is loose and the boundary is obvious before adsorption.The needle-like structure is dense and the boundary is blurred after adsorption.Some vanadium or arsenic elements were detected in the adsorbed scale.The specific surface area,pore volume and pore diameter of the scale decreased after adsorption,indicating that the adsorbed vanadium or arsenic occupied some adsorption sites and pore sites of the scale.?2?The effects of pipe dosage,reaction time,initial concentration of vanadium or arsenic,initial pH of solution,temperature,Cl^-concentration and SO₄^2-concentration all have certain effects on the adsorption of vanadium or arsenic on the scale.The influence factors of the seven influencing factors of vanadium adsorption on vanadium are,from high to low,the initial concentration of vanadium,reaction time,temperature,initial pH,dosage of pipe scale,SO₄^2-concentration,Cl^-concentration;The influence weights of the seven influencing factors are,from high to low,the initial concentration of arsenic,reaction time,initial pH,dosage of pipe scale,temperature,SO₄^2-concentration,and Cl^-concentration.?3?The kinetics of the adsorption of vanadium or arsenic by scale conforms to Lagergen's quasi-second-order non-linear kinetics model at the same time.It shows that there are many adsorption processes for vanadium or arsenic by scale,and the key step to control the adsorption reaction rate is the chemical reaction rate.In addition,the kinetics of adsorption of vanadium or arsenic by scale also conforms to Webber-Morris intraparticle diffusion model.The two straight lines fitted by the intraparticle diffusion model do not pass the origin,which indicates that intraparticle diffusion is not the only speed-limiting step in the process of scale adsorption.?4?The adsorption isotherm process of vanadium or arsenic by pipe scale conforms to Langmuir adsorption isotherm equation.The fitting degree is higher and the saturated adsorption value is close to the measured value.It can better describe the adsorption law of vanadium or arsenic by pipe scale.It also shows that the adsorption process is dominated by single molecular layer adsorption.The adsorption process was fitted by thermodynamic equation.The results showed that the adsorption process of vanadium or arsenic by scale was an entropy-driven spontaneous endothermic process.?5?The adsorption model of vanadium and arsenic was established by response surface analysis method.The model can evaluate the adsorption of vanadium and arsenic by tube scale.