Sulfite-based simultaneous removal of Cr（Ⅵ） and Rhodamine B

Abstract

The wastewater containing both Cr（Ⅵ） and dyes is frequently produced in the industrial manufacturing processes including printing and dyeing，tanning，etc. Based on the concept of “treating waste with waste”，the feasibility of simultaneous removal of Rhodamine B（RhB） and Cr（Ⅵ） by activating sulfite with Cr（Ⅵ）（Cr（Ⅵ）/S（Ⅳ） system） was investigated. The active species in the reaction system were identified，and the effects of initial concentrations of Na2SO3 and Cr（Ⅵ），the initial pH and the amount of dissolved oxygen on the degradation of RhB and Cr（Ⅵ） were investigated. The results showed that，at the initial pH was 3，95.1% of RhB and 87.4% of Cr（Ⅵ） was removed within 60 min by 1.00 mmol/L Na2SO3 and 0.15 mmol/L Cr（Ⅵ）. The dissolved oxygen was involved in the conversion of sulfur-oxygen free radicals in the reaction process，and played a key role in the degradation of RhB and the reduction of Cr（Ⅵ）. The finding of EPR detection and quenching experiments demonstrated that，SO4·-，SO5·-，·OH and 1O2 cooperatively engaged in the reaction process of Cr（Ⅵ）/S（Ⅳ） system，in which SO4·-is the main active species. Meanwhile，the contribution of 1O2 formed from SO4·-should not be ignored. In addition，the possible degradation pathway of RhB was proposed according to the results of ultraviolet full-wavelength scanning and GC/MS.

Keywords

• sulfite
• advanced oxidation process
• radical
• printing and dyeing wastewater