Reduction of Pollutants in the Tanning Industry Using the Reverse Tanning Method against the Physical Properties of Leather

This study aims to tan the skin with reverse tanning based on the order of pH, thereby reducing the use of chemicals and water due to the pH regulation process. The reverse tanning method will result in a faster tanning process and reduce the use of many chemicals, so that the pollutant load released from the tanning process will be much reduced. Conventional leather tanning is carried out through many processes starting from the BHO (Beam House Operation) process, tanning, post-tanning, and finishing; this process is carried out through a 14-15 step process that produces a large number of pollutants. This is because in conventional leather processing a lot of pH adjustment processes are carried out that go back and forth. In this study the leather processing steps were ordered based on the pH of the tanning process, the chemicals and the pH of the process were regulated by the sequence of the process steps to avoid some repeated acidification and basification/neutralization as in conventional leather processing. The process begins with soaking, liming, fleshing, deliming, tanning, dyeing, fatliquoring, and chrome tanning. This process begins with an alkaline pH of 11 and ends with an acidic pH of 3.8. Chrome tanning is done with variations in the amount of chrome of 2%, 3%, 4%. The results showed that leather with 4% chromium produced the highest Ts of 103 °C, tensile strength of 39.86 N, tearing strength of 13.19 N/mm, seam strength of 12.8 N/mm, elongation of 46.87%, Cr content (VI) 1.68 ppm. These results have met the standard ISO/TR 20879:2007 Footwear. The reverse tanning process with a process from high to low pH without adjusting the pH back and forth by adding solutions and salts means reducing liquid waste in the leather tanning process. So, this process can reduce the amount of liquid waste or pollutants.