Migration And Simulation Of Azo Dyes In River Sand

After entering the natural environment,the dye wastewater can move downward with the migration of soil moisture through methods such as leaching,causing potential harm to groundwater.In order to understand the adsorption and migration mechanism of organic azo dyes in soil,this study used static adsorption experiments and column experiments to study the adsorption and migration characteristics of azo dyes in porous river sand,and used HYDRUS-1D software to analyze the experimental results.Numerical simulation is expected to provide a scientific basis for evaluating soil pollution caused by azo dyes.（1）Linear and non-linear adsorption isotherm models were used to fit the adsorption isotherms of AR B and ALY 2G respectively.The Freundlich equations have a certainty coefficient（R²）greater than 0.98,and the Linear equations R²are all greater than 0.95.It can be seen that the Freundlich equation fits the adsorption isotherm better.The adsorption capacity of the river sand to AR B and ALY 2G increases with the increase of the concentration of the equilibrium solution.The fitting parameters of the isotherm adsorption model decrease with the increase of p H.（2）Under different p H,the migration speed of AR B and ALY 2G in river sand is different.The higher the p H,the closer the peak（C/C₀）of the penetration curves of the two dyes is to1.With the increase of p H,the peak time of effluent is shortened gradually,and the dye has better penetration ability and easy migration after entering river sand.（3）With the decrease of initial AR B concentration,the peak time of penetration curve is advanced,and the penetration curve becomes steep.With the increase of pore water velocity from1.019 cm/min to 2.038 cm/min,AR B starts to flow out and ends in advance gradually.When the flow rate is 2.038 cm/min,the peak span of the penetration curve is the widest,and the first outflow reaches its peak.It shows that AR B is easier to migrate with water flow when the flow velocity is too fast.（4）The chemical non-equilibrium single-point adsorption model OSM in HYDRUS-1D software can better describe the migration process of AR B in river sand.The parameter（α）obtained by model inversion is far less than 100,which indicates that the imbalance caused by the difference of adsorption sites plays a leading role in the migration process of AR B in river sand,and there is non-instantaneous adsorption.（5）OSM can better simulate the migration process of ALY 2G in river sand.The adsorption partition coefficient（K_D）obtained by simulation is consistent with the Freundlich isothermal adsorption model fitted by static adsorption experiment,which shows that the adsorption capacity decreases with the increase of p H.（6）Using HYDRUS-1D software to simulate the penetration curves of AR B and ALY 2G,the partition coefficient K_Dvalue was obtained by inversion,and then the retardation factor R_dwas obtained;and in the static adsorption experiment,the retardation was obtained by the Freundlich isotherm adsorption model fitting factor comparison,its value is smaller.