Silica treatment technologies in reverse osmosis for industrial desalination: A review

Abstract

Reverse osmosis (RO) is the main process of current industrial desalination, and its performance is affected by the quality of water source. Natural water contains a certain level of silica, which is originated from metal silicate in the earth crust. Due to its complexity, silica fouling is difficult to control, which often causes less efficient design of RO system for safe operation. In the present work, we review the current state of silica treatment technology in RO desalination. Silica chemistry is investigated in standpoint of the scale formation mechanism among multiple forms of silica species and its synergistic interaction with other foulants such as organic matter. Then, pretreatment methods to remove silica in the RO feed water are outlined. They include softening/coagulation, seed precipitation/aggregation, tight ultrafiltration, ion exchange, adsorbents media, and electro coagulation. We finally highlight the mitigation of RO fouling under silica rich conditions, whose concept can be implemented in different ways of antiscalant dosing, high/low pH operation, and intermediate softening of the RO concentrate, respectively. This review will provide comprehensive information and insight about the optimal operation of industrial RO susceptible to silica fouling.

Effect of feed water composition and pretreatment on the irrigation water for boron-sensitive crops

“…As calcium represents most of the total hardness, its concentration has to be monitored in feed water. Calcium concentrations in the geothermal waters used in this work were low compared to the concentration level where scaling concentrations typi-removed by the RO membrane afterward [31].…”

“…This is later inducted into silica fouling which is very difficult to remove. The existence of divalent cations such as calcium and magnesium promotes the precipitation of silica [31]. Silica fouling on RO membranes then results in significant flux decline reducing the water production capacity [32].…”

The Effect of Silicate Ions on the Separation of Lithium From Geothermal Fluid

“…One of the explanation for that could be the silica polymerization. The (Park et al, 2020). The polymerization of silicic acid occurs rapidly in neutral or slightly alkaline pH values and is formed slowly below pH 6.5 (Putera et al, 2018;Park et al, 2020).…”

“…The (Park et al, 2020). The polymerization of silicic acid occurs rapidly in neutral or slightly alkaline pH values and is formed slowly below pH 6.5 (Putera et al, 2018;Park et al, 2020). Due to a low pH solution (1.8-2.1) after every repetition extraction process, the polymerization of silicic acid actually occurs probably at a slow rate.…”

“…Due to a low pH solution (1.8-2.1) after every repetition extraction process, the polymerization of silicic acid actually occurs probably at a slow rate. With other divalent cations, silica polymerization can be formed because silicic acid is classified as a weak acid in geothermal water (Brown, 2013;Park et al, 2020).…”