Flocculation kinetics of precipitated calcium carbonate (PCC) with sterically stabilized nanocrystalline cellulose (SNCC)

Enhanced flocculation of aluminum oxide particles by lignin-based flocculants in dual polymer systems

Lignin is an abundant phenolic polymer produced vastly in pulping processes that could be further valorized. In this work, anionic (AKLs) and cationic (CKLs) lignin-based polymers were made by polymerizing kraft lignin (KL) with acrylic acid (AA) or [2-(methacryloyloxy) ethyl] trimethyl-ammonium chloride (METAC), respectively. In the polymerization reactions, various molar ratios of AA or METAC to KL were applied to produce AKLs and CKLs with different characteristics. The produced AKLs and CKLs were used in single and dual systems to flocculate aluminum oxide in suspension. To assess the interaction of these lignin-based polymers with the aluminum oxide particles; the zeta potential, adsorption, and flocculation of the colloidal systems were evaluated comprehensively. The flocculation performance of the lignin-derived polymers was compared with that of the homopolymers of AA and METAC (PAA and PMETAC) and commercially used flocculants. In single polymer systems, among the anionic synthesized polymers and homopolymers, KL-A4 (an AKL) was the best flocculant for the aluminum oxide suspensions owing to its largest molecular weight (330 × 10³ g/mol) and highest charge density (-4.2 mmol/g). Remarkably, when KL-A4 and KL-C4 (the CKL with the highest molecular weight and charge density) were used subsequently in a dual polymer system, a larger adsorbed mass and a more viscous adlayer were formed than those of single polymer systems on the surface of aluminum oxide particles. The synergy between KL-A4 and KL-C4 was even stronger than that between homopolymers, which led to more significant adsorption on the aluminum oxide surface and, consequently, more efficient flocculation, producing larger (22 μm) and stronger flocs, regardless of the agitation intensity used in the systems.

Nanocellulose for Sustainable Water Purification

Nanocelluloses (NC) are nature-based sustainable biomaterials, which not only possess cellulosic properties but also have the important hallmarks of nanomaterials, such as large surface area, versatile reactive sites or functionalities, and scaffolding stability to host inorganic nanoparticles. This class of nanomaterials offers new opportunities for a broad spectrum of applications for clean water production that were once thought impractical. This Review covers substantial discussions based on evaluative judgments of the recent literature and technical advancements in the fields of coagulation/flocculation, adsorption, photocatalysis, and membrane filtration for water decontamination through proper understanding of fundamental knowledge of NC, such as purity, crystallinity, surface chemistry and charge, suspension rheology, morphology, mechanical properties, and film stability. To supplement these, discussions on low-cost and scalable NC extraction, new characterizations including solution small-angle X-ray scattering evaluation, and structure-property relationships of NC are also reviewed. Identifying knowledge gaps and drawing perspectives could generate guidance to overcome uncertainties associated with the adaptation of NC-enabled water purification technologies. Furthermore, the topics of simultaneous removal of multipollutants disposal and proper handling of post/spent NC are discussed. We believe NC-enabled remediation nanomaterials can be integrated into a broad range of water treatments, greatly improving the cost-effectiveness and sustainability of water purification.

Cellulose-based dispersants and flocculants

Natural dispersants and flocculants, often referred to as dispersion stabilizers and liquid-solid separators, respectively, have secured a promising role in the bioprocessing community. They have various applications, including in biomedicine and in environmental remediation. A large fraction of existing dispersants and flocculants are synthesized from non-safe chemical compounds such as polyacrylamide and surfactants. Despite numerous advantages of synthetic dispersants and flocculants, issues such as renewability, sustainability, biocompatibility, and cost efficiency have shifted attention towards natural homologues, in particular, cellulose-based ones. Within the past decade, cellulose derivatives, obtained via chemical and mechanical treatments of cellulose fibrils, have successfully been used for these purposes. In this review article, by dividing the functional cellulosic compounds into "polymeric" and "nanoscale" categories, we provide insight into the engineering pathways, the structural frameworks, and surface chemistry of these "green" types of dispersants and flocculants. A summary of their efficiency and the controlling parameters is also accompanied by recent advances in their applications in each section. We are confident that the emergence of cellulose-based dispersing and flocculating agents will extend the boundaries of sustainable green technology.

Cellulose Nanocrystal (CNC)-Latex Nanocomposites: Effect of CNC Hydrophilicity and Charge on Rheological, Mechanical, and Adhesive Properties

Cellulose nanocrystals (CNCs), a sustainable nanomaterial, are in situ incorporated into emulsion-based pressure-sensitive adhesives (PSAs). Commercially available CNCs with different surface hydrophilicity and surface charge (CNC101 and CNC103 from CelluForce) are used to explore their role in PSA property modification. Viscosity measurements and atomic force microscopy reveal differences in degree of association between the CNCs and the latex particles depending on the surface properties of the CNCs. The more hydrophilic and higher surface charge CNCs (CNC101) show less association with the latex particles. Dynamic strain sweep tests are used to analyze the strain-softening of the nanocomposites based on CNC type and loading. The CNC101 nanocomposites soften at lower strains than their CNC103 counterparts. This behavior is confirmed via dynamic frequency tests and modeling of the nanocomposites' storage moduli, which suggest the formation of CNC aggregates of, on average, 3.8 CNC101 and 1.3 CNC103 nanoparticles. Finally, PSA properties, i.e., tack, peel strength, and shear strength, simultaneously increase upon addition of both CNC types, although to different extents. The relationship between the PSA properties and CNC surface properties confirms that the less hydrophilic CNCs lead to improved CNC dispersion in the PSA films and therefore, enhance PSA properties.