Efficient adsorption-photodegradation of 4-nitrophenol in aqueous solution by using ZnO/HZSM-5 nanocomposites

In this paper, the newly prepared ZnO/HZSM-5 nanocomposites were suggested as the promising alternative materials for conventional means of waste water treatment. The combination effect of adsorption–photodegradation for the removal of 4-nitrophenol (4-NPh), as a biorefractory pollutant, occurred successfully when 7 wt.% of ZnO nanoparticles were incorporated in HZSM-5 zeolite. It was found that both the hydrophobicity and size-selectivity of HZSM-5 toward 4-NPh enhanced the adsorption process. The photodegradation of 4-NPh solutions was performed under UV irradiation and the influence of various parameters such as ZnO loading amount, pH dependence and initial concentration of 4-NPh were investigated. The results indicated that during the fixed reaction time (90 min) about 91% total organic carbon of solution, containing 4-NPh (20 mgl− 1) was removed at pH = 5. Batch kinetic studies were conducted to evaluate the adsorption–photodegradation process. The pseudo-second-order fit well over the range of reaction time. It can be suggested that encapsulating ZnO clusters in the zeolites is a proper way to inhibit the agglomeration of ZnO nanoparticles and also to retard the recombination of photogenerated electron–hole in photocatalytic activity.

► ZnO/HZSM-5 nanocomposites are efficiently capable of removing 4-nitrophenol.
► Hydrophobicity and size-selectivity of HZSM-5 enhance the adsorption of 4-Nitrophenol.
► Well-dispersed ZnO nanoparticles on HZSM-5 produce high photocatalytic reactivity.