Plasma-Saline Water Interaction: A Systematic Review

Abstract

Plasma-liquid interaction research has developed substantially in recent years due, mostly, to the numerous applications of cold atmospheric plasma (CAP). Plasma-liquid interactions are influenced by the concentrations of the ionic species present in the liquid environment, and few studies have paid attention to saline water, which generally mediates the reactions in many plasma applications. Therefore, the present review aims to explore the main results and the influence of variables on the modification of properties of saline water by CAP sources following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The searches were carried out in the Scopus, Science Direct, and Web of Science databases, resulting in the inclusion of 37 studies. The main effects of the interaction between CAP and saline water are (i) the production of reactive oxygen and nitrogen species (RONS); (ii) the increase in conductivity and decrease in pH, directly proportional to the increase in discharge voltage; (iii) and the effective area of interaction and the shortest distance between electrode and solution. Other effects are the localized evaporation and crystallization of salts, which make the interaction between plasma and saline water a promising field in the development of technologies for desalination and improvement of liquid properties.

Keywords: DBD; PRISMA; atmospheric plasma; corona discharge; saline water.

Figure 1

Selection flowchart of studies to be reviewed.

Figure 2

Macro-research fields of the included studies in this review. Fundamental [21,41,42,43,44,45,46,47,50,52,54,58,59], plasma medicine [20,22,31,32,38,39,40,48,49,51,55,56,60], engineering [24,25,26,53], and environmental [19,23,27,28,29,30,57].

Figure 3

Distribution of published studies by year and macro research field.

Figure 4

Types of plasma-treated saline water. PBS [22,39,40,44,51,57,60]; NaCl 0.9% [22,47,48,50,51,56,58]; artificial sea water [21,27,28,29,41,42,43,54]; natural sea water [19,20,23,24,25,26,38,59]; other saline solutions [30,31,32,45,46,49,52,53,55].

Figure 5

Schematic configuration of a corona discharge.

Figure 6

Dielectric barrier discharge configuration with (A) parallel and (B) coplanar electrodes.

Figure 7

Plasma generation methods for saline-based water treatment, where PiL refers to the configuration in which the plasma is immersed in the liquid, and PoL to those configurations where the plasma is applied to the surface of the saline liquid.