Component，distribution and formation mechanism of foulant in the process of desulfurization wastewater treatment by membrane distillation

Abstract

The effect of pollutants on flux during the treatment of desulfurization wastewater by polyvinylidene fluoride（PVDF） membranes were investingated. Then，the pioneer pollutants and dominant pollutants causing flux changes at different periods in the treatment process were determined. The flow rate playd a dominant role in the distribution of the membrane fouling layer. A three-dimensional single-phase computational fluid dynamics（CFD） method was used to evaluate the flow state in the membrane module system，while SEM，X-ray energy dispersive spectrometer（SEM-EDS），and FTIR were used to analyze the distribution，composition and structure of pollutants on the membrane surface in the horizontal and vertical directions in different fouling periods. It was found that the change in membrane flux is divided into two main phases： a slowly decreasing phase and a rapidly decreasing phase， and the distinct flux variation in the two phases were attributed to differences in the dominant pollutants. Organic pollutants were the pioneer pollutants that lead to a slow decline in flux in the early stage，and mineral scaling was the dominant factor in the rapid decline of flux in the later stage. Organic pollutants mainly included humic acid and fulvic acid， which first deposited on the membrane surface during the membrane distillation process through hydrophobic-hydrophobic interaction with the membrane surface， causing a slow decrease in flux. Mineral contaminants， mainly calcium sulfate， nucleate and crystallize in the bulk solution as the concentration process， and grew rapidly on the membrane surface resulting in a rapid decrease in flux.

Keywords

• desulfurization wastewater
• membrane distillation
• organic contaminant
• inorganic contaminant
• membrane fouling