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In this work, the influence of pH and ionic strength on the flocculation performance of cationic xylan copolymer in kaolin and bentonite suspensions was systematically investigated. The cationic xylan was produced via copolymerizing xylan with 2-(methacryloyloxy ethyl) trimethylammonium chloride (METAC), and the cationic xylan copolymer (CMX) showed a maximum adsorption of 4.6 and 1.8 mg/g on kaolin and bentonite particles at the CMX dosage of 8 mg/g, pH 10, 30 °C and 1 h, respectively. The reduction in charge density of CMX from 2.66 to 2.48 meq/g was observed, with an increase in pH of CMX solution to from 2 to 10. The maximum increase in the zeta potential of kaolin (+54 mV) and bentonite (−3 mV) suspensions and the highest removal of kaolin (75%) and bentonite (96%) from the suspensions were obtained at 8 mg/g CMX and pH 7. Stability studies revealed that pH had a noticeable influence on the sedimentation of kaolin and bentonite particles. CMX increased the destabilization index of kaolin (0.4–45) and bentonite (0.2–51) suspensions by increasing the floc size of kaolin and bentonite particles to 9.5 μm and 12.7 μm, respectively. CMX removed more of bentonite than kaolin at any pH under static and dynamic conditions. The impact of inorganic salts on the removal of kaolin particles was also studied. CMX exhibited better performance than a commercial flocculant (PDADMAC) in flocculating the commercially produced effluent. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Flocculation is a widely used method to treat wastewater effluents. Aluminum oxide particles have been recognized as major parts of effluents of ceramic industries. In this work, the flocculation of aluminum oxide particles with various sizes (0.06-0.6 μm) was analyzed using poly(acrylic acid) (PAA) to investigate how the flocculation effectiveness of PAA would be affected by the particle size of aluminum oxides. The zeta potential of the suspensions was changed to a similar extent by PAA, regardless of aluminum oxide particle size, implying that the diffuse double layer of the particles was affected in a similar manner despite different adsorption amounts of PAA. The relative turbidity of the suspensions was remarkably reduced for the aluminum oxide with the largest particle size (AL1) and was less affected by aluminum oxide with smaller sizes (AL3). The chord length of the produced flocs was pronouncedly increased by increasing the particle size of aluminum oxide and the floc counts was reduced substantially. The sedimentation studies of the suspensions revealed more efficient sedimentation behavior for AL1/PAA flocs than for AL1 and AL3 based flocs. The settling velocity and sedimentation compactness of the flocs were also analyzed in this study. [ABSTRACT FROM AUTHOR]

The flocculation process is widely used for separating particles from suspension systems. To make this process more environmentally friendly, a biobased flocculant was proposed to be used in this work. This study involves the experimental evaluation of a flocculation system of aluminum oxide particles (with two different sizes) and a kraft lignin-acrylic acid (KL-AA) polymer, as a biobased-flocculant, with advanced tools, such as focused beam reflectance measurement, vertical scanning analyzer, and gravitational scanning analyzer. A statistical framework was adapted to model the experimental results based on the mixture distribution theory, which led to a more in-depth analysis of the shape and size of flocs in the heterogeneous suspension system. The results revealed that the flocculation process of aluminum oxide suspension was altered by the salinity of the medium as well as the size of aluminum oxide particles. It was found that the flocs formed with KL-AA at a higher NaCl concentration had smaller sizes and exhibited higher shear resistance than the flocs formed in the absence of salt. Furthermore, by increasing the concentration of NaCl, the particles tended to possess more spherical shapes. The results also showed that the fractal dimension for flocculated particles increased by concentrating NaCl in the suspensions. Under gravity and centrifugal forces, the impact of KL-AA in flocculating particles was insignificant in the presence of salt. [Display omitted] • Lignin-acrylic acid flocculant was used for treating aluminum oxide suspensions. • Experimental and modeling results confirmed the smaller flocs in saline systems. • The larger particles flocculated and settled faster and generated larger and bulkier flocs. • De-flocculation and re-flocculation of flocs were investigated at different salinity. • The impact of flocculant was less observed in saline system under gravitational forces. [ABSTRACT FROM AUTHOR]