ABSTRACT
A tremendous amount of research has been devoted to fully elucidate the geochemical processes controlling the fate and behavior of phosphate (PO4
3−) and arsenate (AsO4
3−) because of their important roles in environmental processes. Mobility and bioavailability of PO4
3− and AsO4 3− in soil and water are
largely dependent on adsorption-desorption processes on solid phases. It has been demonstrated that both PO4
3− and AsO4 3− oxyanions strongly adsorb
soils and geological media and compete with each other for adsorption sites (Cui and Weng 2013; Hiemstra and Van Riemsdijk 1999; Hingston et al. 1971; Jain and Loeppert 2000; Manning and Goldberg 1996b; Neupane et al. 2014; Roy et al. 1986a; Smith et al. 2002; So et al. 2012; Violante and Pigna 2002; Zhang and Selim 2007; Zhao and Stanforth 2001). The existence of phosphorus (P) can substantially reduce arsenic (As) adsorption and increase As mobility in the vadose zone and aquifer (Bearup et al. 2012; Darland and Inskeep 1997; Melamed et al. 1995; Peryea 1991; Williams et al. 2003; Zhang
CONTENTS
Surface Complexation Models .......................................................................... 151 Empirical Equilibrium Models .......................................................................... 154
Selectivity Coefcient .................................................................................... 154 Langmuir-Type Equilibrium Model ............................................................ 156 Freundlich-Type Equilibrium Model........................................................... 157
Kinetic Multicomponent Models ...................................................................... 158 Langmuir-Type Kinetic Model ..................................................................... 159 Freundlich-Type Kinetic Model ................................................................... 159 Multicomponent Multireaction Model ....................................................... 160
Multicomponent Transport Model ................................................................... 161 Concluding Remarks .......................................................................................... 164 Acknowledgments .............................................................................................. 165 References ............................................................................................................. 165
and Selim 2007), which has caused environmental concern because of widespread As contamination around the world (Smedley and Kinniburgh 2002).
