Crystallization of water-soluble salts poses a considerable threat to the integrity of porous building materials and sculptures. The electrokinetic (EK) desalination process aims to remove salt ions from the fired-clay bricks using a low DC electric field. This study examines the effect of adding buffers, CaCO3 and CH3COOH, to kaolin clay poultice on suppressing the pH changes across electrodes and the removal of NaCl and Na2SO4 salts from brick. In these experiments, an electric field of 1 V cm−1 was applied across the electrodes for different time durations, i.e., 24, 48, and 72 h. The results reveal that the application of poultice effectively suppressed the pH changes in NaCl-contaminated brick samples and significantly enhanced the removal efficiency of both the Na+ (~ 83%) and Clˉ (~ 90.6%) ions. However, in the Na2SO4-contaminated bricks, alkaline fronts intrude the bricks mainly due to CaSO4 generation, creating a mineral barrier that hinders the electromigration of ions. This phenomenon reduces the removal efficiency of Na+ (~ 78%) and <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10800_2024_2245_Article_IEq1.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="40" /> </InlineMediaObject> <EquationSource Format="TEX">$\text{SO}_{4}^{2-}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mtext>SO</mtext> <mrow> <mn>4</mn> </mrow> <mrow> <mn>2</mn> <mo>-</mo> </mrow> </msubsup> </math></EquationSource> </InlineEquation> (~ 57%) ions over 72 h, thereby diminishing the impact of the buffering agent, i.e., CH3COOH in suppressing the alkaline environment during the EK desalination process. Additionally, the highest ion removal rate and energy consumption were observed within the initial 24 h of the EK experiments. However, extending the treatment duration beyond 24 h resulted in a reduced removal rate relative to energy consumption. This decline was attributed to the decreased concentration of salt ions in the pore solution of the brick samples. Graphical abstract

Impact of calcium rich kaolin-clay and salts behavior on electro-desalination of soil bricks

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发表日期：

2025年2月20日

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Farwa Bint E Arshad,
Aasma Akram,
Abdul Ahad Hussain,
Mubashera Ishaq,
Muhammad Afzaal,
Maryam Hina,
Kashif Kamran

摘要

Crystallization of water-soluble salts poses a considerable threat to the integrity of porous building materials and sculptures. The electrokinetic (EK) desalination process aims to remove salt ions from the fired-clay bricks using a low DC electric field. This study examines the effect of adding buffers, CaCO₃ and CH₃COOH, to kaolin clay poultice on suppressing the pH changes across electrodes and the removal of NaCl and Na₂SO₄ salts from brick. In these experiments, an electric field of 1 V cm⁻¹ was applied across the electrodes for different time durations, i.e., 24, 48, and 72 h. The results reveal that the application of poultice effectively suppressed the pH changes in NaCl-contaminated brick samples and significantly enhanced the removal efficiency of both the Na⁺ (~ 83%) and Clˉ (~ 90.6%) ions. However, in the Na₂SO₄-contaminated bricks, alkaline fronts intrude the bricks mainly due to CaSO₄ generation, creating a mineral barrier that hinders the electromigration of ions. This phenomenon reduces the removal efficiency of Na⁺ (~ 78%) and $\text{SO}_{4}^{2-}$ ${SO}_{4}^{2 -}$ (~ 57%) ions over 72 h, thereby diminishing the impact of the buffering agent, i.e., CH₃COOH in suppressing the alkaline environment during the EK desalination process. Additionally, the highest ion removal rate and energy consumption were observed within the initial 24 h of the EK experiments. However, extending the treatment duration beyond 24 h resulted in a reduced removal rate relative to energy consumption. This decline was attributed to the decreased concentration of salt ions in the pore solution of the brick samples.

Graphical abstract