Surface Chemical Aspects of Coagulation, Deposition and Filtration Processes: Part 1. Formulation and Description of Surface Complexation Model for Reactions at Solid-Water Interfaces

Kim, Sung-Jae; Benefield, Larry D.

Environmental Engineering Research 1996;1(2): 107-116.

Sung-Jae Kim^†, and Larry D. Benefield

¹Department of Food Science, Fisheries College, Gyeongsang National University,Tongyeong, Gyeongnain, 650-160, Korea.
²Department of Civil Engineering, Auburn University, Auburn, AL 36849, U.S.A.

Corresponding Author: Sung-Jae Kim ,

Received: March 13, 1996; Accepted: September 13, 1996.

ABSTRACT

The development of all surface complexation models are based on electrostatic adsorption reactions which take place at defined coordination sites (in finite numbers) and then can be described quantitatively via mass law equations. A surface complexation model is a useful tool for several processes such as colloid stability and coagulation, particle deposition and filtration, dissolution, and precipitation of solid phases. In this work, the model development is limited in the diffuse layer (DL) and triple layer (TL) surface complexation models. The equations are written for the reactions on the silanol surface group ( >SiOH) only and reaction among species (H⁺. OH^- , Na⁺, Ca²⁺, CI^- and SO₄^2- ) in solution, except for the formation of water, are not included. Electrostatic effects are included in the mass action laws as multiplicative terms similar to the conentrauon of each species. The entire set of equations can be solved numerically at any pH and electrolyte concentration w.th known values for the interfacial properties. The concentrations of individual surface species are calculated from the expressions including the solution concentrations [>SiOH], the intrinsic equilibrium constants (K""), and the exponential terms of the electrostatic energy (exp( -e$/kT) and exp( -ez^AT)). The charges (<>,„ and o£) and potentials (#„ and jfs) are calculated from charge and potential relationships. The computer algorithm MINTEQA2 was used to compute the DL and TL surface complexation models, which is a computer algorithm for the geochemical equilibrium speciation model for dilute aqueous system.