Effect of chemical and physical factors on the crystallization of calcium sulfate in seawater reverse osmosis brine

Abstract

A major challenge of the seawater reverse osmosis (SWRO) desalination process corresponds to the management of concentrated brine waste because discharging the brine back into the sea through submarine pipelines influences the marine ecosystem and incurs additional costs at coastal RO plants. A membrane distillation crystallizer (MDC) can further produce clean water and simultaneously recover valuable resources from the concentrated brine; this is more environmentally and economically optimal. The SWRO brine contains salts, which contribute to scaling development during the MDC operation. Hence, the main goals of this study include (i) observing the crystallization tendency of calcium sulfate (CaSO4) under high salinity and, (ii) examining other inorganic and organic compounds and operational conditions that affect the CaSO4 crystallization. The crystallization tendency of CaSO4 in SWRO brine 2 was examined with respect to different temperatures; changes in pH values; and in the presence of co-existing ions, chemical agents, and organic matters as well as physical factors. The results showed that the size and quantity of crystals formed increased with increasing heating temperatures. Furthermore, an increase in the pH values (from 5 to 9) increased the crystal size. At higher pH, the complexion of NaCl along with CaSO4 was created. Moreover, stirring 27 enhanced CaSO4 crystal formation due to the kinetic mechanism.

Reclaiming Tropical Saline-Sodic Soils with Gypsum and Cow Manure

“…This effect is probably because cow manure also contains Na + , and its excessive use may go against the desired effect of improving soil chemistry. Although cow manure also contains Ca 2+ , this cation is not as available due to its adsorption to organic compounds, such as citric acid and humic acid, that are also present in the cow manure [34,35]. Thus, the addition of cow manure as a source of organic matter can improve the physical characteristics of the soil, facilitating the release of salts present in the soil solution.…”

Slippery for scaling resistance in membrane distillation: A novel porous micropillared superhydrophobic surface

“…Highly saline wastewater streams from steel, chemical, petrochemical, and mining industries are of key concern for environmental and economical sustainability in developing countries (Latorre 2005, Shannon, Bohn et al 2008, Bouchrit, Boubakri et al 2015, Choi, Naidu et al 2018, Deshmukh, Boo et al 2018. Therefore, concentrating high salinity liquids has become an important task in water treatment.…”

“…MVR and ED not only require high energy but also suffer from corrosion. Membrane distillation (MD) has attracted wide attention for desalinating highly concentrated brine with concentrations up to crystallization (Ji, Curcio et al 2010, Nghiem, Hildinger et al 2011, Edwie and Chung 2013, Chen, Lu et al 2014, Hickenbottom and Cath 2014, Naidu, Jeong et al 2014, Bouchrit, Boubakri et al 2015, Chen, Wang et al 2015, Eykens, Hitsov et al 2016, Gryta 2016, Shin and Sohn 2016, Bouchrit, Boubakri et al 2017, Chen, Tian et al 2017, Chen, Zheng et al 2017, Duong, Hai et al 2017, Junghyun, Heejung et al 2017, Choi, Naidu et al 2018 2018, Kim, Kim et al 2018, Naidu, Zhong et al 2018.…”

Crystallization of CaCO3 in Aqueous Solutions with Extremely High Concentrations of NaCl

“…Actually, Na + and Cl − are the main components and CaCO 3 was the major scale type in concentrated seawater [19]. Earlier, Choi et al and Sheikholeslami et al discovered that NaCl at high concentrations (3.5-5.2 wt.%) delayed the crystallization of CaSO 4 [20,21]. It is of great importance if the CaCO 3 scaling could be delayed when seawater is concentrated by 2-4 times.…”