Electrodeposition of Calcium Carbonate and Magnesium Carbonate from Hard Water on Stainless-Steel Electrode to Prevent Natural Scaling Phenomenon

Faléstine Souiad,Ana Lopes,Annabel Fernandes,Ana Sofia Rodrigues,Lurdes Ciríaco,Maria José Pacheco,Yasmina Bendaoud-Boulahlib

doi:10.3390/w13192752

Faléstine Souiad, Ana Lopes + Show 5 more

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https://doi.org/10.3390/w13192752

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Abstract

This study focuses on preventing scale formation in hard waters by controlled electrode-position of Ca2+ and Mg2+ on a stainless-steel cathode at constant applied current intensity. The influence of the anode material, BDD or Ti/Pt/PbO2, cathode active area, stirring speed, and applied anodic current intensity on the inorganic carbon (IC), Ca2+, and Mg2+ removal was investigated. Assays were performed with model hard water solutions, simulating Bounouara (Algeria) water. The scaling inhibiting properties of the treated water were followed by measuring IC, calcium, and magnesium concentrations and chronoamperometric characterization of the treated solutions. The influence of the Ca/Mg molar ratio on the inorganic carbon removal by electrolysis was also evaluated, utilizing model solutions with different compositions. It was found that an increase in stirring speed or cathode geometric area favors IC and Ca2+ and Mg2+ removal rates. The applied current intensity was varied from 0.025 to 0.5 A, and the best results were obtained for 0.1 A, either in IC and Ca2+ and Mg2+ removals or by the accelerated scaling tests. However, energy costs increase with applied current. The deposit formed over the cathode does not seem to influence posterior deposition rate, and after eight consecutive assays, the solid deposition rate was kept constant. Ca/Mg ratio influences IC removal rate that increases with it. The results showed that hard-water scaling phenomena can be prevented by solid electrodeposition on the cathode at applied constant current.

Highlights

The scaling phenomenon is one of the problems that has taken a large concern in aquatic environmental studies for decades [1,2,3,4,5]
In industrial applications of reverse osmosis technology, considered among the most efficient technologies in wastewater treatment and seawater purification [6,7,8,9], the formation of inorganic scale, which is often characterized by calcium carbonate, calcium sulfate and silica, on membranes surface is considered one of the main factors leading to the reduction of reverse osmosis application/efficiency [10,11,12]
1.7 ± 0.2 mS cm ) and specific energy consumptions per mass of inorganic carbon or calcium and magnesium removed, during electrolytic assays performed at different current intensities

Summary

Introduction

The scaling phenomenon is one of the problems that has taken a large concern in aquatic environmental studies for decades [1,2,3,4,5]. Natural and spontaneous scale formation on metallic surfaces leads to numerous technical and economic problems in several domains, namely in the drinking water distribution system, where the precipitation and accumulation of crystals of insoluble salts over time causes pipes damage by decreasing its internal diameter, which can reach up to 90% after a few years of use [4]. This reduction in pipes’ diameter blocks and decreases the water flow rate. It is very important to find economically viable processes that allow the exploitation of these water resources by reducing technical and economic problems resulting from their utilization

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