Combined use of natural polymers (chitosan and humic acid) for treatment of Ni tailings containing fine particulate material

Abstract

Dewatering unit operations are essential steps in mineral processing routes to obtain materials with high levels of solid content (60-70 wt.%). Polymers have been used for coagulation and flocculation in wastewater treatment for many years, and its application is mostly based on the ad- sorption mechanisms. In the case of fine nickel ore tailings, wastewaters typically contain large amounts of particles within microscale (d50 = 9.5 μm). The use of flocculant polymers, mostly poly- 18 acrylamides, acts to remove colloids from these effluents. Environmentally friendly natural poly- 19 mers, such as chitosan and humic acid, when used combined can be a highly effective reagent for 20 the treatment of these tailings. Therefore, the purpose of this study is to evaluate the use of these 21 natural polymers in the treatment of wastewater containing colloidal material to adequate the fine 22 particles content to less than 50 NTU, satisfying environmental standards. Particle removal effi- 23 ciency was calculated based on turbidity on wastewater as well as on thickener overflow. For fine 24 nickel tailings containing 2.15% (wt./vl.), a mixture of chitosan/humic acid of 24.9/6.3 g/t at pH=6.7 25 achieved a sedimentation of 95 wt.%. The turbidity was reduced to 40 NTU, motivating the use of 26 this technique to adequate wastewater to water reuse.