efficiency of chitosans for the treatment of papermaking process water by dissolved air flotation - sciencedirect
Papermaking process waters were treated with chitosans in dissolved air flotation.At neutral pH, native chitosans were more efficient than quaternary derivatives.A high synergy is obtained when native chitosans are combined with bentonites.Chitosan dosage can be reduced by half if bentonite is added at a ratio 1:2 by weight.FBRM technique allows monitoring flocculation and predicts separation efficiency.
Interest has grown in bio-polymers as being environmental friendly alternatives to synthetic additives. In this work, two native chitosans with different molecular weights have been evaluated on a laboratory scale for their effectiveness for the removal of contaminants from papermaking process waters by dissolved air flotation (DAF). The use of chitosan quaternary derivatives and the use of the native chitosans in combination with anionic bentonite microparticles have also been tested. Results demonstrate a high efficiency of the native chitosan products at intermediate dosages and furthermore, their efficiency is enhanced by the combined addition of bentonite. For an equivalent removal of contaminants, the required dosage of chitosan is about half that the dosage required in absence of bentonite. Quaternary derivatives have not improved the efficiency of the native chitosan in this case. The optimum treatment would be 50mg/L of nativechitosan and 100mg/L of bentonite where this treatment is capable of the removal of 8389% turbidity (residual turbidity 210320 NTU), 6871% dissolved turbidity (residual dissolved turbidity of 2224 NTU), 1822% total solids (residual total solids of 27502900mg/L) and 1923% COD (14401525mg/L). The low molecular weight native chitosan is more efficient than the medium molecular weight chitosan in all cases. The Focused Beam Reflectance Measurement (FBRM) is used to assess the aggregation process and to predict the separation efficiency of DAF units either with single or dual systems. The efficiency predicted through the FBRM technique is very similar to that obtained later in the DAF tests.
the interaction between cations in saline water and calcium bentonite in copper flotation | springerlink
In this study, the effect of cations, Na+ and Mg2+, in saline water on copper flotation in the presence of calcium bentonite was investigated. It was found that as the concentration of NaCl was increased, the copper recovery initially decreased and then increased to above 99%, while the copper grade initially increased and then decreased. In contrast, as the concentration of MgCl2 was increased, the copper recovery continuously increased, while the copper grade continuously decreased. The variation of copper recovery and grade was mainly attributed to the synergistic effect of pulp rheology and flotation solution chemistry. The underpinning mechanisms are the compressing electrical double layer and ion-exchange interaction between saline water and bentonite, which occur at the same time. Using saline water slightly affected the pulp rheology with a decrease in copper recovery at low NaCl concentration. Increasing the concentration of cations in saline water might even facilitate the flowing out of exchangeable cations, especially divalent cations, from the interlayer space of bentonite to the solution, resulting in the decrease of copper grade at high salt concentration.
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The authors greatly acknowledge the financial support from the Natural Science Foundation of Hunan Province, China (No. 2019JJ50835). The authors would also like to thank Mr. Tianran Fang (graduate, Central South University) for his contribution to this paper.
Huang, L., Song, S., Gu, G. et al. The Interaction between Cations in Saline Water and Calcium Bentonite in Copper Flotation.
Mining, Metallurgy & Exploration 38, 693699 (2021). https://doi.org/10.1007/s42461-020-00297-4
the interaction of clay minerals with gypsum and its effects on coppergold flotation - sciencedirect
Kaolinite affects flotation through entrainment.Bentonite network structures decrease flotation kinetics.Gypsum in ores with a high clay mineral content can change the flotation outcome.Gypsum inhibits the formation of bentonite network structures.Flotation in the presence of clay minerals depends on clay particle associations.
The interaction of two clay minerals, kaolinite and bentonite with gypsum and its effects on the flotation of a coppergold ore was investigated in this study. It was found that bentonite increased the viscosity more than kaolinite when mixed with the coppergold ore at low shear rates. The detrimental effect of these clay minerals on flotation was attributed to the entrainment of clay particles when kaolinite was added to the ore and to a decrease in true flotation by bentonite. Bentonite formed a sponge-like structure with predominant edgeedge (EE) interactions which might affect hydrodynamics in the flotation cell and have a detrimental effect on flotation recovery. Kaolinite did not form a particular network structure and its aggregates mostly consisted of faceface (FF) type associations which did not affect flotation hydrodynamics. The addition of gypsum to the orebentonite mixture inhibited the formation of interconnected network structures. This led to lower viscosity values with flotation behaviour similar to that of mixtures with kaolinite. In this case, there was an improvement in recovery, but the grade decreased due to entrainment. The addition of gypsum to the orekaolinite mixture created aggregates with long strings further enhancing particle entrainment with more mass transported to the froth.