We shall now employ both simulations and theory to investigate CR mechanism in suspensions containing multivalent ions. The results presented are for weak acidic surface groups of pK a = 5.4. All ions are treated as hard spheres of radius r i = 2 Å. Nanoparticles are hard spheres of radius a = 6 nm with Z surface adsorption sites. For theory we will use SHC of radius R c = 12.4 nm. To explore the accuracy of the mPB equation, we start by considering nanoparticles of fixed charge. Once convinced of the accuracy of the mPB approximation for 1:z electrolyte, we will proceed to investigate charge regulation and construct the tritation isotherms, which we will then compare to simulations for different salt concentrations and charge asymmetries.