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Removal of Cr(vi) from wastewater by a two-step method of oxalic acid reduction-modified fly ash adsorption
Xiaoling Jiang1, Wenqiang Fan2, Chunqing Li2
1Hebei Provincial Key Laboratory of Green Chemical Technology and High Efficient Energy Saving, Tianjin Key Laboratory of Chemical Process Safety, School of Chemical Engineering and Technology, Hebei University of Technology Tianjin 300130 China 1991033@hebut.edu.cn +86-13132143286.
Abstract:
Excessive Cr(vi) emissions have been and continue to be a major contributor to heavy-metal pollution; recently, the development of a low-cost, safe and efficient method for the removal of Cr has attracted significant attention. In the present study, a two-step method involving oxalic acid reduction and modified fly ash adsorption was developed. The experimental results showed that this methodology exhibited high Cr(vi) removal efficiency under the following conditions: 1.5 g L-1 of oxalic acid, modification of fly ash (FA) by 20 wt% KOH, a contact time of 2 h and a mass of 0.3 g of modified fly ash (MFA) at room temperature (15-25 °C). The influencing factors of the adsorbent were discussed by characterized for their elemental composition, functional groups, surface area and surface morphology. According to the characteristic parameters and q e, the isothermal adsorption process could be well-described by the Langmuir model. The adsorption process resembles more closely to the pseudo-second-order kinetic model. In conclusion, this two-step method of oxalic acid reduction-modified fly ash adsorption is promising for Cr(vi) removal.
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