Polyacrylamide grafted cellulose as an eco-friendly flocculant: Key factors optimization of flocculation to surfactant effluent

Sustainable formulation polymers for home, beauty and personal care: challenges and opportunities

As society moves towards a net-zero future, the need to adopt more sustainable polymers is well understood, and as well as plastics, less visible formulation polymers should also be included within this shift. As researchers, industries and consumers move towards more sustainable products there is a clear need to define what sustainability means in fast moving consumer goods and how it can be considered at the design stage. In this perspective key challenges in achieving sustainable formulation polymers are highlighted, and opportunities to overcome them are presented.

Moringa oleifera seed defatted press cake based biocoagulant for the treatment of coal beneficiation plant effluent

This study proposes a unique way of preparation of biocoagulant from Moringa oleifera defatted seed press cake. The press cake used in this study is a waste material produced as a by-product during cold press oil making from Moring oleifera seeds. The prepared Moringa oleifera seed defatted press cake based biocoagulant was found more effective than presently used metallic and polymer-based coagulants and flocculants for removal of fine particles of colloidal size from the effluent generated in the process of coal beneficiation. The detailed characterization of Moringa oleifera defatted seed press cake and the prepared biocoagulant for Particle size, Field Emission Scanning Electron Microscopy, Energy Dispersive X-Ray analysis, Zeta Potential, Fourier-transform Infrared Spectroscopy, etc. was done. The biocoagulant has been found effective in 97.4% total suspended solids removal and 97.48% turbidity removal from coal beneficiation plant effluent. The biocoagulant has been found to work satisfactorily under high fluxes of turbidity and total suspended solids with high removal of fine particles. The age of biocoagulant had negligible effect on fine particle removal efficiency (97.4% for fresh to 95% for 3-week-old biocoagulant). Field Emission Scanning Electron Microscopy analysis reveals considerable increase in flocs size from 198 nm to a 20 μ size well-developed flocs. The biocoagulant has proved as an efficient substitute of the metallic and polymer-based coagulants for the efficient treatment of coal beneficiation plant effluent.

Effect of rapid-mixing conditions on the evolution of micro-flocs to final aggregates during two-stage alum addition

In a coagulation-flocculation process, optimal separation of the resultant aggregates plays a decisive role on coagulation performance and provides a lower burden for subsequent treatment units. This separation highly depends on the stability of the micro-flocs formed during the initial, rapid stage of coagulation. In this work, a two-stage addition of aluminium sulphate (alum, Al₂(SO₄)₃) was employed by adding 0.04 and 0.08 mM Al₂(SO₄)₃ at the beginning and the end of rapid mixing, respectively. The coagulation performance and floc characteristics were compared to conventional single addition with the same total coagulant dosage, and the effects of variable rapid-mixing speeds (160-850 rpm) and duration time (10-120 s) were investigated. The results showed that the residual turbidity of two-stage coagulant addition was 85.1% lower than single addition when applied at a mixing speed of 580 rpm and a duration time of 120 s. The underlying coagulation mechanism revealed that the two-step addition more effectively neutralized colloids and formed larger aggregates that settled better and could more easily be removed. Moreover, the aggregates were less firm, which was attributed to different interactions among the micro-flocs, the second addition of Al₂(SO₄)₃ and destabilized colloids. The present work provides data to broaden the window of rapid-mixing environments for more effective coagulation.

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.

Optimization of coagulation pre-treatment for alleviating ultrafiltration membrane fouling: The role of floc properties on Al species

This study investigated membrane fouling in a coagulation/ultrafiltration (C-UF) process by comparing the floc properties and humic acid (HA) removal efficiency of three hydrous Al(III) species (Al_a, Al_b, and Al_c). The results indicated that the coagulation and membrane mechanisms were different for all three Al species because of the differences in floc properties. The HA removal efficiency increased with increasing Al dosage until an equilibrium was reached at the optimal dosage of 6 mg L^-1. In addition, membrane fouling gradually decreased as the Al dosages increased. Regardless of coagulant type, the OH and COOH functional groups of HA reacted with the Al species. Both external and internal membrane fouling were strongly dependent on the porosity of the cake layer and on the size distribution of the floc particulates, respectively. The pore area of the cake layer formed by the Al_a-coagulated effluent was large because of the strong charge neutralization. Moreover, Al_a generated large and loose flocs with a porous cake layer that mitigated external fouling. However, the internal fouling with the Al_c coagulant was significant because the concentration of residual aggregates in the membrane pores was high.

Polyacrylamide and poly(N,N-dimethylacrylamide) grafted cellulose nanocrystals as efficient flocculants for kaolin suspension

Natural polymer flocculants for wastewater treatment have received close attention in recent years. Here we used two flocculants, polyacrylamide and poly(N,N-dimethylacrylamide) grafted cellulose nanocrystals synthesized by a "macro-RAFT assisted" strategy, for the flocculation of kaolin suspension. The flocculation performance of these two flocculants, including flocculants dosage, settling time and floc size, was carefully studied and compared. Results suggested that poly(N,N-dimethylacrylamide) grafted cellulose nanocrstyals showed better flocculation performance than polyacrylamide grafted ones. Meanwhile, their flocculation behavior was also compared with other cellulose-based flocculants in literature and we suggested polymer modified cellulose nanocrstals as flocculants might have higher flocculation performance, but this needs further verification.

An efficiently sustainable dextran-based flocculant: Synthesis, characterization and flocculation

Polysaccharide-modified flocculant is a notable material in the field of wastewater treatment. Synthesis of biopolysaccharide derivatives as eco-friendly flocculants is remarkably desired for environmental protection. This work presents an efficient flocculant synthesized through copolymerization of acrylamide, sodium acrylate (AS), and dextran. Physicochemical properties of the flocculant were evaluated. Process parameters of coal-washing wastewater flocculation were tested using Response Surface Method. The application of graft polymers exhibited efficient flocculation performance at low level of flocculant dosage in alkalescent environment. The improved dextran contributes to handle industrial effluent and sanitary sewage.