An analytical solution to contaminant diffusion in semi-infinite clayey soils with piecewise linear adsorption

► Piecewise linear adsorption isotherm was proposed to approximate nonlinear adsorption. ► Moving boundary was used to model saturation adsorption of contaminant. ► Analytical solution for diffusion with piecewise linear adsorption was presented. ► Proposed analytical solutions agree well with experimental data. ► Model using secant of Freundlich isotherm results in lower breakthrough time.