Technical and Economic Evaluation and Selection of Sulfate ION Removal Technologies for Recovery of Water from Mineral Concentrate Transport Slurry

Abstract

This paper presents the findings of a comprehensive evaluation for a Primary Mineral Processing (PMP) company that contracted Battelle to identify economical technology to remove sulfate ion (SO 4 2-) from mineral slurry transport (MST) water, now disposed of as a waste, for reuse or sale. MST water is separated from product by dewatering a sulfidic mineral concentrate slurry prior to loading and shipping of the solid product. The MST water sulfate ion concentration is between 400 and 1720 mg/L, below the high concentrations for which technologies such as lime precipitation, crystallization, and evaporation are favorable, and above low concentrations that are amenable to ion exchange technology, reuse, or release. In addition, the salt concentrations fluctuate significantly causing processing issues with a number of purification technologies. The technical target is to reduce sulfate levels to < 500 mg/L SO 4 2-to allow water reuse, and especially to < 250 mg/L SO 4 2-(drinking water requirements) to provide the broadest reuse options. Based on company criteria of proven technology, operability, minimum residuals, and cost effectiveness in meeting the requirements for sulfate reduction, the two top-rated technologies recommended were ettringite production and precipitation using aluminum oxide, and electrochemical salt splitting.

Properties of recycled sludge formed from different aluminiferous reagents during the ettringite process

“…Despite this, other authors have described Al(OH)3 being used as reagent in sulfate removal (e.g. [25] albeit with longer reported reaction times of 30-300 min. [ ] report the use of amorphous Al(OH)3 at a dose of 0.784 g/L which reduced sulfate concentrations from 1043 ppm to 213 ppm in 15 min.…”

A Critical Review of Alternative Desalination Technologies for Smart Waterflooding

“…Sulfate Precipitation With Chemical Reagents. Bowell (2004) and Usinowicz et al (2005) reviewed all the available technologies to remove sulfate ions from mine water. Both these studies concluded that sulfate removal through precipitation of ettringite can provide one most-efficient treatment solution.…”

“…In the SAVMIN process, aluminum is recovered for recycling from ettringite, whereas the CESR process disposes of the precipitated ettringite as sludge without aluminum recovery. The key precipita-tion reaction occurring in both of these sulfate-removal processes with industrial water is as follows (Usinowicz et al 2005):…”

A Critical Review of Water Chemistry Alteration Technologies to Develop Novel Water Treatment Schemes for SmartWater Flooding in Carbonate Reservoirs

“…Bowel (2004) and Usinowicz et al (2006) reviewed all the available technologies to remove sulfate ions from mine water. Both these studies concluded that sulfate removal through precipitation of ettringite can provide one most efficient treatment solution.…”

“…In the SAVMIN process, aluminum is recovered for recycle from ettringite whereas CESR process disposes the precipitated ettringite as sludge without aluminum recovery. The key precipitation reaction occurring in both these sulfate removal processes with industrial water is shown below (Usinowicz et al 2006).…”