Heterogeneous catalytic degradation of nonylphenol using persulphate activated by natural pyrite: response surface methodology modelling and optimisation

The degradation of nonylphenol polyethoxylates (NPEOs) was investigated by persulphate (PS) activated using naturally pyrite semi-conductor mineral (NP-SCM) in aqueous solutions. The effects of various factors including solution pH, NP-SCM dosage, NPEOs and PS concentration were examined through response surface methodology (RSM) and Box-Behnken design (BBD) technique. The properties of NP-SCM were characterised by FESEM, BET, XRD and EDX analyses. The results showed that the RSM model had a well correlation (R-2 > 0.99) between the predicted data and the experimental findings of NPEOs degradation. In addition, under the optimum conditions (PS = 5.85 mM, pH = 3.0, NP-SCM = 0.85 g/L and NPEOs = 10 mu M), the removal efficiency of NPEOs reached more than 99%. The maximum removal efficiency of COD and TOC was obtained 87% and 80% at 90 min reaction time, respectively. The negative effect of various competing ions on the removal of NPEOs was as phosphate>bicarbonate>copper>nitrate>calcium>ammonium. After five successive catalyst cycles reuse, the degradation efficiency was insignificantly decreased from 99.6% to 90.5%, which indicated the excellent potential reusability of NP-SCM catalyst. It can be concluded that NP-SCM along with PS, due to the generation of highly reactive oxidising species (SO4BLACK CIRCLE-), its simplicity and easy separation of the catalyst, has a great potential for the degradation of NPEOs from aqueous solutions.

Automated summary

The degradation of nonylphenol polyethoxylates (NPEOs) using persulphate (PS) activated by naturally pyrite semi-conductor mineral (NP-SCM) in aqueous solutions was investigated. The response surface methodology (RSM) and Box-Behnken design (BBD) technique were used to analyze the effects of various factors. The results showed that under the optimum conditions, the removal efficiency of NPEOs reached more than 99% and the NP-SCM catalyst exhibited good reusability.