Research into the application of n-butylamine to recycle solid waste of tannery containing

Abstract

Chromium-containing solid waste of tanneries in Vietnam has so far been treated by burial or incineration in industrial incinerators. Recycling solid waste from tanneries is capable of not only creating products with high values but also solving environmental pollution. Economic profits lie in the use of recovered chromium and the obtained protein. In previous studies, MgO was used in hydrolysis to maintain solution’s pH. However, the ash and chromium content in protein recovered from this method were at high levells, 7-25% and 50-150 ppm, respectively. Researchers modified this technology by substituting part of MgO with volatile organic bases, namely n-butylamine (99.5%) to hydrolyse chromium-containing solid waste in alkaline environment with alcalase enzyme (Alcalase 2.5 UI/g). The researchers developed a one-stage process to recycle chromium-containing waste solid of tanneries and identified values of temperature, pH, enzyme, and n-butylamine mass for complete resolution of the waste. This method reduced the hydrolysis time from 6-8 hours to 3 hours), and reduced 20% of hydrolysis product cost. The recovered gelatin products (humidity <15%, ash content <2%, Pb<0.5 mg/kg, As<0.5 mg/kg, Pt<0.1 mg/kg, Cr<1 ppm) that meet the QCVN-4-21:2011/BYT standard can be used as material for other industries, and chromium sludge can be reused. This study paved the way for recycling of waste containing chromium from tanning, which is unprecedented in Vietnam.