Removal of nitrite ions from aqueous solutions by protonated poly(NN-dimethylamino ethylmethacrylate) hydrogels (P(DMAEMA)) was investigated. We have shown that polycationic and pendant secondary arnme group containing P(DMAEMA) hydogels is very efficient and highly selective for the removal of nitrite ions from aqueous solutions at even in very high concentrations. Adsorption studies have shown that pH of the nitrite solution has influence on the nitrite ion uptake capacity of P(DN/LAEMA) hydrogels. The adsorption capacity of hydrogels had been increased up to 3100 mg NO2-1/g dry gel, by changing pH of the solution. The results of the adsorption studies showed that the interaction between nitrite ions and quaternized arnine groups agree with the Langmuir-type isotherm. (c) 2006 Wiley Periodicals, Inc.