recycling of chromium-containing leather waste: incorporation of phosphorus and potassium for the production of a slow release macronutrient npk fertilizer after chromium removal

摘要

RECYCLING OF CHROME CONTAINING LEATHER WASTE: INCORPORATION OF PHOSPHORUS AND POTASSIUM FOR THE PRODUCTION OF A NPK FERTILIZER WITH SLOW RELEASE OF CHROMOTERS. The present invention relates to the process of obtaining a slow release NPK fertilizer by incorporating phosphorus and potassium into the treated leather tailings. To this end, the chromium (III) contained in the sawdust, shavings and flaps of chrome-tanned leather is extracted, that is, solid tannery residues from the lowering of the leather. In this way, a high nitrogen collagen solid material is obtained which, when enriched with phosphorus and potassium, has potential for application in agriculture. The incorporation of mineral P and K is accomplished by adsorption using solutions of the salts KCI and KH ~ 2 ~ PO ~ 4 ~ in different concentrations and in pH consistent with that used in soils to ensure greater plant development. Another application of chromium free residual solid material is its use in the production of biopolymers. Chromium extraction from tannery solid waste consists of the use of a low cost complexing agent, as well as mild extraction conditions, avoiding solid dissolution. In addition, the compound formed by chromium and the complexing agent (Cr (III) -complexing) is separated by the addition of sodium hydroxide, which allows the regeneration of the complexing agent, allowing its reuse in a new extraction process. After precipitation of the chromium present in the solution of Cr (III) -compexant with sodium hydroxide in the form of chromium hydroxide (Cr (OH) ~ 3 ~) is added sulfuric acid thereby obtaining chromium sulfate, which may be later used in the tanning process of new leather pieces.