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2 Physicochemical Problems of Mineral Processing

2 2022

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Polymeric flocculants based on the interfacial characteristics of fine clay minerals : a review

100%

Zhang L. , Min F. , Wang L. , Shu Q.

tom Vol. 58, iss. 4

art. no. 149652

Fine clay minerals, found in various industrial effluents, have attracted much attention in recent times. They can form a highly stable suspension in water and increase the complexity of sedimentation for the treatment of wastewater. In the past few decades, the flocculation of fine clay minerals has been significantly improved due to numerous design advancements in the molecular weight, charge density and structure of polymeric flocculants. In this article, the interfacial characteristics and affecting factors of clay minerals are discussed, the design, synthesis and application of synthetic polymers, natural polymers and natural-based grafted polymers are reviewed, as well as the advantages and disadvantages of three types of polymers. The development direction of upgrading existing clay mineral flocculants is proposed based on the interfacial characteristics of clay minerals. Weakening the hydration of clay minerals, altering the manner of molecular interaction and precisely controlling the structure of polymer chains are the design objectives of novel polymeric flocculants.

Study of flocculation performance and mechanism of ultrafine montmorillonite particles with NPAM

88%

Wang L. , Min F. , Chen J. , Wang T. , Zhou Z.

tom Vol. 58, iss. 3

art. no. 147790

Ultrafine montmorillonite particles are the main clay minerals in industrial wastewater. In order to explore the flocculation performance and mechanism of flocculant with montmorillonite, the effects of nonionic polyacrylamide (NPAM) dosage and molecular weight on flocculation effect were studied using a flocculation sedimentation experiment. The morphology of flocs was observed by metallographic microscope and scanning electron microscope, and the microscopic adsorption mechanism was studied utilizing density functional theory (DFT). The results show that the best reagent system for the montmorillonite sample is that the molecular weight of NPAM is 14 million and the added amount is 100 g/t. The floc size increases with rising NPAM dosage, forming a unique multi-level compact space network structure through polymer bridging. The adsorption energy of acrylamide on the Na-(001) surface of montmorillonite is -108.81 kJ/mol, which is significantly higher than -50.66 kJ/mol on the None-(001) surface. Hydrogen bonding is not the main reason for the adsorption of acrylamide on the montmorillonite surface. NPAM mainly causes the flocculation and sedimentation of montmorillonite through the processes of polymer bridging and electrostatic attraction. This study can provide a theoretical basis for the design and synthesis of new flocculants.