A Cleaner Deliming Process Using Sodium Gluconate for Reduction in Nitrogen Pollution in Leather Manufacture

Abstract

Ammonium salts used in deliming process are the main sourceof high ammonia nitrogen (NH3-N) concentration in tannerywastewater. To reduce nitrogen pollution in leather manufacturewithout sacrificing quality of resultant leathers, a cleanerdeliming agent prepared by mixing sodium gluconate (60 wt.%),citric acid (15 wt.%) and ammonium sulfate (25 wt.%) togetherwas employed for deliming limed cattle hide pelt. The resultsindicated that this cleaner deliming agent penetrated the wholepelt very quickly and successfully formed a buffer system of pH8-9 with the alkali from liming, which prevented acid swellingand damage to the fiber network of pelt. The delimed pelt had acleaner grain surface with a higher extent of calcium removalthan the conventional ammonium delimed pelt. Theconcentrations of NH3-N and total nitrogen (TN) in the cleanerdeliming effluent were dramatically reduced by 86% and 79%,respectively. Moreover, the cleaner deliming scarcely affectedsubsequent bating process with trypsin.