Inhibitory effect of Hydrex anti-scalant on calcium scale deposition from seawater under multiple-effect distillers' conditions

Abstract

a b s t r a c tIn this work, the inhibitory effect of a commercial anti-scalant (Veolia Hydrex s 9209) on the calcium minerals of carbonate, sulfate and hydrocalumite (Ca/Al) clay deposition from seawater has been investigated. Different concentration factors and anti-scalant doses were studied by analyzing the water hardness and turbidity. The inhibitory effect of the investigated anti-scalant was efficient even at lower concentrations. The percentage inhibition decreases with increasing the temperature and increases with increasing the dose/amount of the anti-scalant. The carbonate scale inhibition was 499% and 98-99% at 50 and 70°C, respectively. The percentage inhibition of sulfate from hemihydrate was ranged from 80% to 87% for 2 and 8 ppm anti-scalant at 50°C. The inhibition of Ca/Al hydrocalumite deposition increases from 70% to 90% upon increasing the dose from 3 to 5 ppm, respectively. A recommended useful dose of antiscalant for seawater is 5 ppm.

Elucidation of dual-mode inhibition mechanism of a typical polymer-based antiscalant on Red seawater for thermal desalination at higher temperatures and higher concentration factors

“…There have been many research group working on the development of various antiscalant and their efficiencies for scale inhibition (Al-Rawajfeh et al, 2015;Boels and Witkamp, 2011;Chen et al, 2015;Gallup and von Hirtz, 2015;Kazi et al, 2012;Li et al, 2015;Patel and Finan, 1999;Rahman and Amjad, 2010;Sheikhi et al, 2016;Singh, 2017;Teng et al, 2016;Vidic et al, 2015), but there are few studies which are exploring the higher concentration of feed water (conc. seawater/ brine) and extended temperature conditions into the account (Ketrane et al, 2009).…”

“…Similarly, there exists a delicate balance of calcium and CO 3 ¯ ¯ in the seawater to support multiple natural phenomena and underwater life (Benjamin, 2010;Stumm, 1995). CaCO 3 formation in seawater is a result of several chemical equilibria viz., dissolution of CO 2 gas, carboxylic acid formation, dehydration of carboxylic acid, protonation of CO 3 ¯ ¯ ion, hydrolysis of calcium hydroxide and equilibrium between calcium and carbonate as depicted in equations 1-5 (Al-Rawajfeh et al, 2015;Alahmad, 2008;Benjamin, 2010).…”