# Research on a Reductive Deep Chlorine Removal Process for Breaking Through the Solid Film Barrier
## 4 Conclusions  
In response to the issues with the current copper slag dechlorination process, this study proposes a new deep dechlorination process based on liquid-phase reduction. Through a comparative analysis of thermodynamic parameters and experimental validation, the following conclusions are drawn.  
1. The ascorbic acid dechlorination process showed significant advantages over copper slag dechlorination. Its potential difference \(\Delta\)E was 0.091 V higher, the reaction-driving force was enhanced by 18.6%, the standard Gibbs free energy \(\Delta\)G\({}^{\text{0}}\) was 59.3% lower, and the equilibrium constant K was 6.7 \(\times\) 10\({}^{9}\) times higher. This indicates that the dechlorination of ascorbic acid has stronger spontaneity and a more complete reaction, and a higher purification depth can be achieved.
2. Under optimized conditions (initial pH 3.6, n(Cu\({}^{2+}\))/ n(Cl\({}^{-}\))/n(H\({}_{2}\)A) = 1.25:1:0.75, 20 \({}^{\circ}\)C, 20 min), the chloride concentration was reduced from 1 g/L to 0.0917 g/L with 90.8% removal. The ascorbic acid dechlorination process achieved rapid dechlorination through its unique end structure, and the reaction process was a homogeneous aqueous phase reaction, with simple and easy-to-control diffusion steps, which avoided the limitations posed by the solid film barrier and possessed higher flexibility and reaction efficiency than copper slag dechlorination.  
The experimental study on the dechlorination of ascorbic acid showed that ascorbic acid as a reducing agent has a good removal effect on chloride ions. Compared to the traditional copper slag dechlorination method, the ascorbic acid method demonstrates higher reaction efficiency. Additionally, for the removal of the same molar amount of chloride ions, the reagent consumption of the copper slag method is significantly higher than that of ascorbic acid. Therefore, from a reagent cost perspective, the ascorbic acid dechlorination method offers a certain economic advantage. In future industrial applications, attention should be paid to the impact of temperature on dechlorination efficiency. At the same time, given the organic nature of ascorbic acid, the subsequent organic substances produced need to be properly treated according to the specific production process of the enterprise, such as through adsorption, oxidation, or other technologies, to reduce the accumulation of organic substances.  
Conceptualization, R.L. and J.L.; formal analysis, R.L. and A.W.; funding acquisition, J.L.; investigation, R.L. and A.W.; methodology, environment, R.L. and J.L.; project administration, J.L.; resources, J.L.; supervision, J.L.; validation, R.L.; visualization, R.L. and A.W.; writing--original draft, R.L.; writing--review and editing, J.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Yunnan Provincial Science and Technology Key Project (No. 202201 AS070031), the NSFC Regional Fund (No. 52264050), and the Kunming University of Science and Technology (Yunnan Province) \"double first-class\" science and technology project (No. 202302 AG050008).  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
The authors declare no conflicts of interest.