Evaluation and comparison of the ammonia adsorption capacity of titanosilicates ETS-4 and ETS-10 and aluminotitanosilicates ETAS-4 and ETAS-10

Due to the well-known adsorption properties of titanosilicates (ETS-4 and ETS-10) and aluminotitanosilicates (ETAS-4 and ETAS-10), it was considered particularly interesting to investigate their efficiency in adsorbing ammonia from a gaseous phase. Prior to testing their adsorption capacity, materials thus synthesized have been analyzed by appropriate characterization techniques. Afterward, the adsorption capacity of microporous materials toward ammonia has been evaluated by measuring the corresponding adsorption isotherms through batch experiments. Experimental measurements were best fitted by a linear constant relationship. From the experimental results, high adsorption capacity values were found for all microporous materials in correspondence of high gaseous ammonia concentration values. In particular, ETAS-10 attained the maximum value of adsorption potential, equal to 7.647 mg of NH3 per g of material. This was likely due to the presence of the acid site linked to the Al atom in its structure with respect to the ETS structure. In addition to that the greater pore size characterizing the phase 10 compared to phase 4 might have entailed a more selective sorption of ammonia molecule. Overall, both titanosilicates and aluminotitanosilicates showed a great adsorption potential toward ammonia. However, materials achieved their maximum capacity at high pollutant loading.