A study of the effect of Si:Al Ratio and ion-exchange on the ability of the zeolite ZSM-5 to adsorb common analgesics from waste water

Abstract

Due to the expansion of the pharmaceutical industry, the increase in demand and current inadequate removal methods, pharmaceutical waste has been increasing in concentration in environmental waters. It is unknown what the chronic effects this waste could have on humans and so more adequate removal methods are necessary. In this research project the zeolite ZSM-5’s effectiveness at removing the analgesics paracetamol, aspirin and ibuprofen lysine from aqueous solution was investigated. ZSM-5’s Si:Al ratio and charge balancing cation were also altered to ascertain the effects these attributes had on its ability to remove the analgesics from aqueous solution. Its ability to remove low concentrations of paracetamol from solution was also investigated. Ion exchange reactions were performed on commercial ZSM-5 ammonium with a Si:Al ratio of 30:1, this being the baseline zeolite for this research, changing the charge balancing cations to iron and sodium respectively. SEM-EDX spectroscopy was ran to ensure the ion exchanges had been successful. Then adsorption reactions using 0.005M paracetamol, 0.005M aspirin and 0.002M ibuprofen lysine were performed on commercial ZSM-5 ammonium with a 30:1 Si:Al ratio and one with a 200-400:1 Si:Al ratio as well as the iron ion exchanged ZSM-5 30:1 ratio and the sodium ion exchanged ZSM-5 30:1 ratio. Using HPLC and powder XRD analysis it was found that the optimum form of ZSM-5 for the adsorption of paracetamol and ibuprofen lysine was the commercial ZSM-5 ammonium with the 30:1 ratio, found to be due to its increased number of ammonium cations present relative to the other forms, and commercial ZSM-5 ammonium with a Si:Al ratio of 200-400:1 the optimum form for the adsorption of aspirin, found to be due to its hydrophobicity. At halved and quartered batch concentrations for paracetamol commercial ZSM-5 ammonium 30:1 was found to have a much lower ability to adsorb paracetamol, adsorbing only 3.62% at max at the halved concentration, relatively small when compared to its maximum of 64.39% at normal concentration.