Bicarbonate Alternatives in the Neutralization Phase of Leather Tanning to Ensure Sustainability

Abstract

The post-tanning procedure involves neutralizing the iso-electric point, which ensures that there is no imbalance between carboxylic groups and amino groups. This balance allows for the penetration of dyes, fatliquoring agents, and other chemical materials. Bicarbonate is used during the neutralization phase, and to eliminate it, 4 metric tons of water are needed for each metric ton of leather. Additionally, this leads to an elevation in both Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). The objective of the research was to substitute bicarbonate with sodium borate, sodium acetate, and sodium formate, and neutralise syntan to decrease the quantities of pollutants generated from this process, minimize the consumption of water, and improve the quality of the produced leather. Each experimental group's BOD, COD, microscopic micrographs, physical, chemical, and organoleptic parameters were determined. The use of sodium borate, neutralizing syntan, sodium acetate, and sodium formate resulted in a significant decrease in the discharge of BOD, COD, and water consumption. Furthermore, the use of 2.5% sodium borate has proven to be the most effective neutralizing agent in reducing water consumption by 80%, total oxygen demand by 39% and costs of neutralization chemicals by 0.62%. Also, the physical and chemical properties of the leather product were similar to those of the control. Therefore, the leather that has been neutralized with sodium borate is considered to have the best organoleptic characteristics compared to the control.