Equilibrium studies of the uptake of aromatic compounds from an aqueous solution by montmorillonite modified with tetraphenylphosphonium and amyltriphenylphosphonium

•Organic-modified montmorillonite could adsorb aromatics from an aqueous solution.•An adsorption can be expressed by Langmuir-type adsorption isotherms.•The adsorption is spontaneous.

Montmorillonite (MMT) modified with tetraphenylphosphonium (TPP⋅MMT) and amyltriphenylphosphonium (AmylTPP⋅MMT) was shown to adsorb 1,2-dimethoxybenzene (DMB) and 1,3-dinitrobenzene (DNB) from an aqueous solution. The adsorption of DMB could be expressed by Langmuir-type adsorption isotherms. The adsorption of DMB by TPP⋅MMT and AmylTPP⋅MMT was spontaneous because the ΔG values in both cases were negative. The uptake of DMB by TPP⋅MMT and AmylTPP⋅MMT could be considered a physical adsorption process caused by π–π stacking interactions, because the ΔG values were in the range of −20 to 0 kJ mol−1. The uptake of DNB by TPP⋅MMT was expressed by the Halsey and Henderson models, which explained the multilayer adsorption.