Modified chemical mineralization-alkali neutralization technology: Mineralization behavior at high iron concentrations and its application in sulfur acid spent pickling solution. (30th June 2022)

• Record Type: Journal Article
• Authors: Wang, Xiaomeng; Wang, Dan; Xu, Jingang; Fu, Jingran; Zheng, Guanyu; Zhou, Lixiang
• Is Part Of: Water research. Volume 218(2022)
• Publication Date: 2022-06-30
• Subjects: Chemical mineralization -- Strongly acidic wastewater -- Alkali neutralization -- Secondary iron mineral -- Arsenite adsorption; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.118513
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Mineralization-neutralization technology was used to treat spent pickling solution. Gelation phenomena appeared in high Fe solutions with large SO4 2− /Fe 2+ molar ratio. Dilution and precipitation with Ba or Ca salts could optimize mineralization condition. Above 90% of iron and most of ions were eliminated during mineralization period. The resultant secondary iron mineral had a high adsorption capacity toward arsenate. Abstract: Mineralization coupled with neutralization is a dual-function technology for disposing acidic iron-rich waters, which can recover the valuable iron in the form of secondary mineral and concurrently purify the wastewater. In this study, a modified technology for treating high Fe wastewater (sulfur acid spent pickling liquor, 62 g Fe/L) was proposed based on the specific investigation of the mineralization behaviors in Fe concentration range of 20–70 g/L. Results showed that high SO4 2− /Fe 2+ molar ratio (> 2.0) tended to trigger gelation phenomena at Fe concentrations above 30 g/L. Fe specie distribution suggested that the insufficient polymerization among Fe-OH complexes might be responsible for the gelation phenomena, since the strong Fe-SO4 coordination almost completely suppressed the Fex (OH)y (3x-y)+ form (a general terms of Fe 3+ hydrolysates and their polymers). Modified mineralization strategies were proposed, including pretreatment with dilution or BaCl2 /CaCl2 precipitation, of which CaCl2 pretreatment was a versatile and low-cost method. Following CaCl2 pretreatment, chemical mineralization converted above 90% of iron into secondary mineral, which therefore drastically reduced the alkali consumption (from 164.2 g/L to 1.4 g/L) and sludge yield (from 328.1 g/L to 2.4 g/L) in subsequent neutralization treatment. The resultant mineral was identified as schwertmannite, and exhibited efficient adsorption capacity toward arsenite (364.2 mg/g). The modified chemical mineralization-alkaline neutralization is a cost-effective technology for the treatment of the acidic iron-rich waters. In practical applications, several regulating strategies should be further explored to improve the mineral purity, and the mineralization conditions must be optimized according to the Fe and SO4 2− concentrations in wastewater. Graphical abstract: Image, graphical abstract