Abstract
Filtration of aqueous liquids has wide implications, for example for provision of clean drinking water. Nevertheless, many people still lack access to safe water and suffer from preventable water-borne microbial diseases. This study reports a new ultrafiltration-range separation technology using a gelatinous layer of aluminium hydroxide polyhydrate as a secondary membrane on a retaining fabric that enables simple and cost-effective production of filtered water. Properties include at least 4-fold higher flux rates than currently available membranes, pressure-resistance, impenetrability to filtered particles, easy cleaning by backwashing and simple, cost-effective replacement by gel injection. Depending on the substrate, filtration is achieved through a packed bed of 1–2 nm hydrate gel globules, partly by mechanical straining with a size exclusion of approx. 10 nm and partly by physical adsorption. As a result, filtration of water (e.g. turbid river water) contaminated with colloids and microorganisms, including viruses, yields clear water that is free of measurable particles or detectable microorganisms. However, small water-soluble molecules (salts, sugars, proteins) remain in the filtrate. The findings demonstrate the potential for wide applicability of hydrate gels in high-flux and low-cost water purification devices.
Highlights
Much progress has been made in the development of filtration and separation devices
We hypothesized that water molecules can exchange through polyhydrate agglomerates of aluminium hydroxide hydrate when placed on a support mesh, allowing a flow of water
To test whether aluminium hydroxide polyhydrate gel can be used as a filter for water-based liquids, aluminium hydroxide hydrate was produced in situ in an aqueous solution by mixing aluminium sulphate and sodium bicarbonate solutions (Reaction 1) or by electrolysis of saline water using aluminium electrodes and DC current
Summary
Filtration of aqueous liquids has wide implications, for example for provision of clean drinking water. This study reports a new ultrafiltration-range separation technology using a gelatinous layer of aluminium hydroxide polyhydrate as a secondary membrane on a retaining fabric that enables simple and cost-effective production of filtered water. The findings demonstrate the potential for wide applicability of hydrate gels in high-flux and low-cost water purification devices. Much progress has been made in the development of filtration and separation devices These include microfilters, high-pressure membranes (e.g. ultrafilters, nanofilters, reverse osmosis, membrane bioreactors) for various applications, including water purification and the isolation of valuable compounds[1,2,3,4,5]. The present study developed a new secondary membrane, aluminium hydroxide polyhydrate, as a filter for aqueous liquids with potentially wide implications. The present study shows that the mode of operation of an aluminium hydroxide polyhydrate filter placed onto a support mesh is potentially quite different to the operation of conventional ultrafiltration membranes
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