Synthesis And Flocculation Properties Of A Cellulose-based Flocculant

Flocculation is just an essential process in industrial wastewater treatment, which plays akey role in solid-liquid separation by aggregation of colloidal particles. It is found thatflocculation process can be more cost effective, easier to operate and lower energy consumptionthan alternative wastewater treatment. Nowadays, flocculant can be divided into three principalcatagories: inorganic flocculants, organic flocculants and microbial flocculants. What’s more,organic flocculants can distinguish as organic synthetic polymer flocculant and natural polymerflocculant. Because of feasible availability, resource recycling, low cost, environmentfriendliness of biodegradability and non-toxic, academic and society draw more and moreattention on the development of natural polumer flocculant. Cellulose is considered as one ofthe most suitable skeleton materials for eco-friendly flocculant. In addition, Zhejiang Provinceis famous for the enormous abundant of Phyllostachys heterocycla bamboo sources. Preparationof a novel efficient and eco-friendly flocculant based on Phyllostachys heterocycla bamboo cannoy only reduce production cost, improve the economic benefit, but also expand the applicationfield of bamboo fiber, even improve the added value of products.In this work, the synthetic conditions of an eco-friendly flocculant based on the cellulosefrom Phyllostachys heterocycla were optimized and the properties such as flocculation effet,biodegradability, etc. were investigated. In other sides, in order to ensure the stability andefficience, the operation conditions of cellulose-based flocculant were optimized, too. And itwas verified by treating with effluent from paper mill. The dye decolorization properties of thenovel cellulose-based flocculant were also studied. The flocculation mechanism wasinvestigated by adsorption kinetics experiment.1. Synthesis of an eco-friendly flocculant based on the cellulose from Phyllostachysheterocycla and its flocculation effect and biodegradationThis work presents a synthesis process and flocculation characteristics of an eco-friendlyflocculant based on bamboo pulp cellulose (BPC) from Phyllostachys heterocycla.Ployacrylamide (PAM) was grafted onto the BPC by free-radical graft copolymerization inhomogeneous aqueous solution. The optimal synthesis conditions of the bamboo pulpcellulose-graft-ployacrylamide (BPC-g-PAM) flocculant were as follows: reaction temperature at50C, APS to BPC mass ratio at0.25g/g, PAM to BPC mass ratio at1g/g, reaction time at1h and the concentration of BPC at4wt%. The average turbidity removal reached98%, whichfurther confirmed the effectiveness of the optimal synthesis conditions. The grafting ratio andthe substitution degree of the sample were43.8%and1.31, respectively, which showedevidence anout the high utilization of cellulose monomers. The biodegradation experimentindicated that the weight loss of the sample could come to above65%via immersing in the soilextracting solution for30days. In view of these facts, the sample had excellent flocculationcapacity and biodegradability.2. Expriment on influence of flocculation condition factors and its optimized operationconditionsThe operation conditions of BPC-g-PAM flocculant sample were optimized byinvestigating the influence of pH, Zeta potential, the dosage of flooculant and coagulant,stirring intensity and time, temperature, etc. The results showed that the BPC-g-PAM flocculantwas negatively charged and the optimized operation conditions were as follows: neutralcondition of PH, the room temperature, flocculant dosage is100mg/L, coagulant dosage of2.5%CaCl2is30mL/500mL, rapid stirring at200rpm for3min, followed by7min of slowstirring at80rpm. The flocculation mechanism was bridging effect. The stability and efficienceof the optimized operation conditions were then verified by treating with effluent from papermill. The results showed that the COD removal rate was about26.5%, BOD removal rate wasabout24.2%, turbidity removal rate was99.28%and the total solids content of concentrate andsuspended solids content after processing all remained trace.3. Properties of dye decolorization of BPC-g-PAM flocculant and its adsorption kineticsmechanismThe dye decolorization experiment of BPC-g-PAM flocculant was undertaken on the basisof results of the optimal synthesis conditions and operation conditions. From the decolorizationresults of cationic dyes and disperse dyes solutions treated by BPC-g-PAM flocculant, it can befound that the BPC-g-PAM flocculant has a excellent dye decolourization capality in bothcolour removal rate and turbidity removal rate. The decolorization rate of disperse dyes treatedby BPC-g-PAM can reach96.65%, while the chroma can decrease to5°, in the allowed rangeof the national standards of dye wastewater discharging. The results of adsorption kinetics experiment of dye decolorization claimed that the adsorption curve more conformed topseudo-second-order kinetic models and the flocculation mechanism of this process was chargeneutralization.