Structural modification of hydroxamic acid collectors to enhance the flotation performance of malachite and associated mechanism

Ammonium-Amine Co-Activation: Promoting the Sulfurization of Azurite and Its Effect on Xanthate Adsorption

Enhanced sulfurization has always been the focus of research on the flotation of copper oxide minerals. In this study, combined ammonium-amine salts were innovatively applied to improve the sulfurization of azurite. Flotation tests were carried out to evaluate the promoting effect of ammonium-amine co-activation on the sulfurization-xanthate flotation of azurite, and the microstructure evolution of sulfurized products was investigated to reveal the mechanism underlying this promoting effect. Compared with single ammonium (amine) salt activation, ammonium-amine co-activation improved the floatability of azurite to a greater extent, i.e., the flotation recovery increased by over 4 percentage points. ToF-SIMS, ICP-OES, FESEM-EDS, AFM, XRD, and UV-vis analyses indicated that ammonium-amine co-activation combined the advantages of inorganic ammonium for buffering pH and organic amine for copper ion complexation, thus promoting the growth of sulfurized crystal products (covellite) and enhancing the adhesion stability of sulfurized products on azurite. Therefore, increasing amounts of copper sulfide components were generated under the ammonium-amine-Na2S system, promoting the adsorption of additional xanthate on azurite. This study provides theoretical support for the application of combined ammonium-amine salts for the sulfurization flotation of copper oxide.

High-efficiency adsorption removal for Cu(II) and Ni(II) using a novel acylamino dihydroxamic acid chelating resin

Cu/Ni-bearing wastewater contamination has recently been a challenge for the environmental protection worldwide. Herein, a novel poly(2-acrylamide-pentanedihydroxamic acid) (PAPDA) resin containing -CONHOH and -COOH groups was prepared and applied to effectively remove Cu²⁺ and Ni²⁺ from heavy metal wastewater. The batch adsorption experiments revealed that the maximum adsorption capacities of PAPDA resin for Cu²⁺ and Ni²⁺ were 436.08 and 195.05 mg·g^-1, respectively, which were 10.20 and 9.45 times higher than that of polyacrylic resin. Specifically, the adsorption kinetics and thermodynamics of PAPDA were respectively consistent with the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating that the adsorption is a single-layer chemisorption process. Besides, the adsorption mechanism was investigated by SEM, XRD, FT-IR, XPS, DFT calculations, suggesting that the PAPDA resin possessing abundant active sites could effectively adsorb the heavy metal ions. Noticeably, the -CONHOH groups represented the strong affinity towards Cu²⁺ and Ni²⁺ by forming stable five-membered rings. In addition, column experiments were conducted to study the practical adsorption process of PAPDA resin to heavy metal ions. Overall, the results proved that the novel PAPDA resin as a green and highly efficient adsorbent has a promising potential for the treatment of heavy metals-containing wastewater.