Remediation of oxalate in a homogeneous granulation process in the frame of crystallization

College

Gokongwei College of Engineering

Department/Unit

Chemical Engineering

Document Type

Article

Source Title

Chemical Engineering Communications

Publication Date

2021

Abstract

Oxalate is a common contaminant found in industrial wastewater, particularly in bauxite refining industries. Crystallization in fluidized-bed processes has been established to be effective toward eliminating the problems associated with sludge disposal. In this study, the effects of oxalate removal in a simulated wastewater were investigated at varying initial oxalate concentration (150 mg/L to 450 mg/L), oxalate to calcium molar ratio (1:2 to 2:1), influent flow rate (0.6 L/h to 1.9 L/h) and pH (4.5 to 8.5) through an unseeded crystallization setup. A homogeneous granulation process in a fluidized-bed reactor was continuously operated for 110 h. The final crystal products were characterized using the scanning electron microscopy and X-ray diffraction analyses. Results showed that the ideal operating conditions for oxalate granulation were at 300 mg/L initial oxalate concentration, 1:1 molar ratio, 0.9 L/h influent flow rate and pH 6.5. These conditions have led to high efficiencies of granulation and total oxalate removal of 94.6% and 96.0%, respectively. For crystal characterization, more than 0.149 mm were formed at a cumulative mass of 67.4% to 67.7%. Furthermore, the results obtained from the characterization of the granule products confirmed the development of spherical pellet-shaped calcium oxalate monohydrate crystals.

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Digitial Object Identifier (DOI)

10.1080/00986445.2021.1887152

Disciplines

Chemical Engineering

Keywords

Sewage—Purification; Oxalates; Crystallization

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