Abstract

At mining deposits in Chile, copper and Molybdenum are extracted together and then separated in a concentration process consisting of several froth flotation and depression steps of chalcopyrite and molybdenite (copper and molybdenum ores, respectively). In this process sodium hydrosulfide (NaHS) is broadly used as depressant of copper ores. However, there are environmental issues related to toxic hydrosulfide gas emissions and pestilent odor, which affects nearby communities and suppose a risk for workers. A no toxic alternative to NaHS is the utilization of lignosulfonates (LS). These lignin derivatives have shown excellent depressant properties in experimental copper-molybdenum flotation trials. To reduce the inherent risk of dealing with NaHS while addressing environmental issues and to increase the amount of recovered copper and molybdenum. In this work we propose the production of LS from kraft lignin as depressant reagents for mining processes. For this four commercial LS (sodium LS low-Mw (~8,000) and high-Mw (~52,000), calcium LS and sugared sodium LS) was evaluated for determine the conditions and efficiency on test of microflotation. The tests were carried out using different reagents for pH adjustments (KOH, CaO). In parallel to this, Pinus radiata lignin was isolated from black liquor through acidification by using H2SO4 at 30% and 50ºC. The Sulfuric Acid Lignin (SAL) obtained was sulfonating it with a mixture of sodium sulfite and formaldehyde for produce experimental LS. Preparation and the analysis of soluble sulfonated lignin from kraft lignin were optimized with the purpose of increasing the effect depressant of LS. Test of microflotation of commercial LS showed that sugared sodium LS and calcium LS have higher efficiency as depressants of chalcopyrite and molybdenite from minerals at pH 9 in the presence thionocarbamate. New analysis and test of microflotation are being performed to evaluate the efficiency experimental LS obtained from sulfonated kraft lignin.