Excellent Flocculation Performance Research Articles

Synthesis of chitosan-based grafting magnetic flocculants for flocculation of kaolin suspensions

A series of novel chitosan-based magnetic flocculants FS@CTS-P(AM-DMC) was prepared by molecular structure control. The characterization results showed that FS@CTS-P(AM-DMC) had a uniform size of about 21.46 nm, featuring a typical core-shell structure, and the average coating layer thickness of CTS-P(AM-DMC) was about 5.03 nm. FS@CTS-P(AM-DMC) exhibited excellent flocculation performance for kaolin suspension, achieved 92.54% turbidity removal efficiency under dosage of 150 mg/L, pH 7.0, even at high turbidity (2000 NTU) with a removal efficiency of 96.96%. The flocculation mechanism was revealed to be dominated by charge neutralization under acidic and neutral conditions, while adsorption and bridging effects play an important role in alkaline environments. The properties of magnetic aggregates during flocculation, breakage, and regeneration were studied at different pH levels and dosages. In the process of magnetophoretic, magnetic particles collide and adsorb with kaolin particles continuously due to magnetic and electrostatic attraction, transform into magnetic chain clusters, and then further form three-dimensional network magnetic aggregates that can capture free kaolin particles and other chain clusters. Particle image velocimetry confirmed the formation of eddy current of magnetic flocs and experienced three stages: acceleration, stabilization, and deceleration.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant.

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Mussel-Inspired Catechol-Grafted Quaternized Chitosan Flocculant for Efficiently Treating Suspended Particles and Refractory Soluble Organic Pollutants

It remains challenging yet of great importance to develop a qualified biopolymer-derived flocculant in treating complex high-salinity wastewaters polluted by suspended solids and refractory soluble organic substances such as organic dyes. The key to this success is to endow the developed flocculants with versatile intermolecular and interfacial interactions in high salinity to trigger effective flocculation. Herein, inspired by mussel’s powerful wet adhesion in a salted marine environment to diverse interfaces, we develop a mussel-inspired chitosan-based flocculant (CQ-CS) by simultaneously grafting catechol and cationic trimethylammonium groups to chitosan backbones. Compared with its cationic compartment, the optimal dosage of CQ-CS is decreased greatly after introducing catechol groups. Moreover, CQ-CS works in a wide pH range from 2 to 7 and can achieve more than 95% removal efficiency of soluble organic dyes and suspended particles such as anionic dyes and kaolin clay at the optimal dosages. More importantly, the flocculation performance of CQ-CS exhibits excellent tolerance to the salinity. As NaCl concentration increases from 0 to 2000 mg/L, CQ-CS maintained similar removal efficiencies for organic dyes, while the removal efficiency of quaternized chitosan (Q-CS) for organic dyes decreased by approximately 8% at this salinity. Finally, CQ-CS exhibits excellent flocculation performance to industrial dyeing wastewaters.

Synthesis and evaluation of cationic polyacrylamide and polyacrylate flocculants for harvesting freshwater and marine microalgae

• Cationic PAETAC & PAmPTAC were synthesized by UV-induced radical polymerization. • New polymers showed good flocculation performance of freshwater & marine microalgae. • Optimal doses of PAETAC were 50 and 4.8 mg/g for C. vulgaris & P. purpureum. • PAETAC and PAmPTAC produced stable flocs, supporting simple dewatering step. This study addresses the challenge of microalgae harvesting through the development of flocculants. Two positively charged cationic polymers including poly[2 (acryloyloxy)ethyl]trimethylammonium chloride (PAETAC) and poly(3 acrylamidopropyl)trimethylammonium chloride (PAmPTAC) were synthesized using the UV-induced radical polymerization, for harvesting both freshwater and marine microalgae. The results show that the synthesized polymers have excellent flocculation performance for both freshwater green microalgae ( Chlorella vulgaris) and marine red microalgae ( Porphyridium purpureum). PAETAC outperformed PAmPTAC for both Chlorella vulgaris and Porphyridium purpureum microalgae. The optimal PAETAC doses for Chlorella vulgaris and Porphyridium purpureum microalgae were 50 and 4.8 mg/g of dry biomass while the optimal PAmPTAC doses were 252 and 35 mg/g of dry biomass respectively. Additionally, the floc formation with the PAETAC was more stable than PAmPTAC, which supported the dewatering step via sieving. The superior performance can be attributed to the higher molecular weight of the PAETAC polymer when compared to the PAmPTAC polymer. In comparison to commercially available polydiallyldimethylammonium chloride (PolyDADMAC), the newly synthesised PAETAC and PAmPTAC polymers demonstrated superior flocculation efficiency at a lower dose. The findings of this study established a platform technology for designing and synthesising cationic flocculants for use in microalgae harvesting.

Enhanced removal of phosphate from wastewater by precipitation coupled with flocculation

Eco-friendly flocculants of alginic acid, NaHCO3 and CaCl2.2H2O with advantages of strong gelation characteristics were prepared for supporting the removal of phosphate in synthetic wastewater using CaO and Ca(OH)2 as precipitants. The effects of weight ratios of each component in flocculants, dosage of flocculants and initial phosphate concentration were investigated through batch of experiments. The results showed excellent flocculation performance with the weight ratio of alginic acid:NaHCO3 and CaCl2.2H2O at 1:0.3:0.02 and the dosage of flocculants at 0.0050 g/25 mL of phosphate solution in the range of initial phosphate concentration from 50 to 1000 ppm. Comparing to the sample without flocculants, the phosphate removal efficiency using CaO and Ca(OH)2 with the addition of flocculants increased from 19 and 20% to 97% at the initial phosphate concentration of 50 ppm, respectively by filtration of filter paper 2.7 μm.

Preparation and Characterization of High-Efficiency Magnetic Heavy Metal Capture Flocculants

In this study, a high-efficiency magnetic heavy metal flocculant MF@AA was prepared based on carboxymethyl chitosan and magnetic Fe3O4. It was characterized by SEM, FTIR, XPS, XRD and VSM, and the Cu(II) removal rate was used as the evaluation basis for the preparation process. The effects of AMPS content, total monomer concentration, photoinitiator concentration and reaction time on the performance of MF@AA flocculation to remove Cu(II) were studied. The characterization results show that MF@AA has been successfully prepared and exhibits good magnetic induction characteristics. The synthesis results show that under the conditions of 10% AMPS content, 35% total monomer concentration, 0.04% photoinitiator concentration, and 1.5 h reaction time, the best yield of MF@AA is 77.69%. The best removal rate is 87.65%. In addition, the response surface optimization of the synthesis process of MF@AA was performed. The optimal synthesis ratio was finally determined as iron content 6.5%, CMFS: 29.5%, AM: 53.9%, AMPS: 10.1%. High-efficiency magnetic heavy metal flocculant MF@AA shows excellent flocculation performance in removing Cu(II). This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove Cu(II) in wastewater.

Synthesis of an Eco-friendly Bamboo Cellulose-grafted-ployacrylamide Flocculant and Its Flocculation Performance on Papermaking Wastewater

Flocculation is the first and important step to remove suspended and slightly soluble pollutants in industrial wastewater treatment. Flocculant is just the key element for flocculation process. Polyacrylamide (PAM) is the most widely used flocculant. But it still holds some potential flaws which are ignored by people. An eco-friendly bamboo cellulose-grafted-ployacrylamide flocculant (BC-g-PAM) was then synthesized by free-radical graft copolymerization in homogeneous aqueous solution. The optimal synthesis conditions of the BC-g-PAM was investigated. FTIR, TG, XRD and FESEM were employed to characterize and define its molecular structure and physical characteristics. The BC-g-PAM was also adopted to treat an actual papermaking wastewater. The positive results showed that the BC-g-PAM exhibited an excellent flocculation performance on the papermaking wastewater. The average turbidity removal rate reached 99.7 % and related suspended solids exhibited the corresponding decline. This flocculation also caused a positive effect on the reduction of CODCr and BOD5 of the wastewater. Meanwhile, the BC-g-PAM exhibited an excellent biodegradability. Its degradation rate reached 63.4 % at 90 d in soil extracting solution.

Heavy metal removal from aqueous solutions by chitosan-based magnetic composite flocculants

In this study, three magnetic flocculants with different chelating groups, namely, carboxymethyl chitosan-modified Fe3O4 flocculant (MC), acrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCM), and 2-acrylamide-2-methylpropanesulfonic acid copolyacrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCAA) were prepared, synthesized, and characterized by photopolymerization technology. They were applied to the flocculation removal of Cr(III), Co(II), and Pb(II). The effect of flocculation condition on the removal performance of Cr(III), Co(II), and Pb(II) was studied. Characterization results show that the three magnetic carboxymethyl chitosan-based flocculants have been successfully prepared with good magnetic induction properties. Flocculation results show that the removal rates of MC, MCM, and MCAA on Cr(III) are 51.79%, 82.33%, and 91.42%, respectively, under the conditions of 80 mg/L flocculant, pH value of 6, reaction time of 1.5 hr, G value of 200 s−1, and precipitation magnetic field strength of 120 mT. The removal rates of Co(II) by MC, MCM, and MCAA are 54.33%, 84.99%, and 90.49%, respectively. The removal rates of Pb(II) by MC, MCM, and MCAA are 61.54%, 91.32%, and 95.74%, respectively. MCAA shows good flocculation performance in composite heavy metal-simulated wastewater. The magnetic carboxymethyl chitosan-based flocculant shows excellent flocculation performance in removing soluble heavy metals. This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove heavy metals in wastewater.

A microblock structure type of anionic flocculant for hematite wastewater treatment: template copolymerization mechanism and enhanced flocculation effect.

In this study, a novel anionic template polymer (TPAS) with microblock structure was prepared by ultraviolet light (UV)-assisted template copolymerization (UV-TP). Acrylamide (AM) and sodium styrene sulfonate (SSS) were selected as monomers and polypropylene ammonium chloride (PAAC) was chosen as the template. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and thermogravimetry/differential scanning calorimetry (TG/DSC) were used to characterize the polymer chemical structure. The results showed that the attractive anionic microblock structure was formed in TPAS. Besides, the association constant (KM) and template reaction kinetics analysis results indicated that the polymerization reaction followed I (ZIP) template copolymerization mechanism. It proved the microblock structure formation again. The anionic microblock structure in TPAM could greatly improve the ability of charge neutralization, electrical patching, and bridging. After the hematite wastewater was conditioned by TPAS with this novel anionic microblock structure, the generated hematite flocs had larger particle size and denser structure. It was favorable for the reduction of turbidity, and the turbidity removal rate could reach 97.8%. TPAS showed excellent flocculation performance for hematite wastewater and had a broad market application prospect.

Advanced reclamation of hairwork dyeing effluent using tree-shaped cellulose flocculants and subsequent optimization of dual-membrane performance and fouling behavior

The purpose of this study is to prepare eco-friendly cationic tree-shaped cellulose-based flocculants (CLFs) through ultrasonic modification as the primary pretreatment, and then realize advanced hairwork dyeing effluent (HDE) reclamation by coupling with dual membrane process. The results showed that the optimal CLF-10 could be obtained by extra ultrasonic processing with a certain conservative time to tune its microstructure appearing in a well-veined and fluffy tree-shaped morphology with relatively uniform particle size distribution. The excellent flocculation performance of CLF-10 in terms of turbidity, total organic carbon (TOC) and dissolved organic carbon (DOC) removal rates reached up to 99.1%, 72.1% and 70.5% at the dosage of 100 mg L−1, and the largest and most dense flocs (Amean of 269 900 μm2 and Df of 1.80) were formed accordingly. This is precisely because the above mentioned microstructure properties enable it to have smaller steric hindrance effect and more active sites, thus effectively clustering the largest amount of target contaminants. Consequently, the bench-scale test employed CLF-10 agent achieved a higher HDE recovery rate of 80.3% under the circumstance of lower operating pressure and significantly mitigated membrane fouling, and the final cleaner reuse water only contained 76.2 mg⋅L−1 of total dissolved solids (TDS), 23.9 mg CaCO3·L−1 of total hardness and 1.85 mg·L−1 of DOC.

Synthesis of Grafted Cationic Starch with DMDAAC Using Ammonium Persulfate/Carbamide Initiation System

Using ammonium persulfate (APS)/carbamide initiation system, cationic grafted starch was prepared by the graft copolymerization of starch with diallydimethylammonium chloride (DMDAAC). The synthesized polymer was confirmed by FTIR, NMR, and XRD. And the morphology was characterized by SEM. The optimum conditions of graft copolymerization were determined and the flocculation properties of the cationic grafted starch were investigated using diatomite suspension. The obtained results showed that grafting ratio (G) and grafting efficiency (GE) have an increased trend along with the increase of mass ratio of starch to monomer. G, GE and cationic degree (DC) increased with the rise of mole ratio of AM to DMDAAC. When the total concentration of the monomers in the system is fixed, increasing APS concentration up to 0.33×10-3 M caused a rise for the G, GE and DC. The optimum temperature and the time were 40 °C and 5 h, respectively. The result also showed that the cationic grafted starch has excellent flocculation performance whether in acid, alkaline or neutral conditions.

Synthesis of the Hydrophobic Cationic Polyacrylamide (PADD) Initiated by Ultrasonic and its Flocculation and Treatment of Coal Mine Wastewater

In this study, a new type of hydrophobic cationic polyacrylamide P (AM-DMC-DABC) (PADD) was synthesized by ultrasonic (US)-initiated polymerization, which is used for the separation and removal of coal mine wastewater. The acrylamide (AM), methacryloyloxyethyl trimethyl ammonium chloride (DMC) and acryloyloxyethyl dimethylbenzyl ammonium chloride (DABC) were used as monomers to prepare). The factors that affecting the US initiated polymerization of PADD were analyzed. Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR) and scanning electron microscopy (SEM) were used to characterize the chemical structure, thermal decomposition performance and surface morphology of the polymers. FT-IR and 1H NMR results showed that PADD was successfully synthesized. In addition, irregular porous surface morphology of PADD were observed by SEM analysis. Under the optimum conditions (pH = 7.0, flocculant dosage = 16.0 mg/L), the excellent flocculation performance (turbidity removal rate (TR) = 98.8%), floc size d50 = 513.467 μm, fractal dimension (Df) = 1.61, flocculation kinetics (KN0) = 27.24 × 10−3·s−1) was obtained by using high-efficiency flocculant PADD. Zeta potential analysis was used to further explore the possible flocculation mechanism of removal. The zeta potential and flocculation analytical results displayed that the flocculation removal process of coal mine wastewater mainly included hydrophobic effect, adsorption, bridging and charge neutralization, and electric patching when PADD was used. The PADD showed more excellent coal mine wastewater flocculation performance than PAD, commercial cationic polyacrylamide (CPAM) CCPAM and PAM. Thus PADD, with its good flocculation effect on coal mine wastewater under relatively wide pH range, had bright practical application value.

An Effective Flocculation Method to the Kaolin Wastewater Treatment by a Cationic Polyacrylamide (CPAM): Preparation, Characterization, and Flocculation Performance

P(AM-DMC) (PAD) was synthesized by ultraviolet- (UV-) initiated copolymerization with methacryloxyethyl trimethyl ammonium chloride (DMC) and acrylamide (AM) as the monomers and initiator 2,2-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as the photoinitiator. Parameters that affect the molecular weight were reviewed by using the single-factor approach. The results showed that the molecular weight (MW) of PAD could come to 7.88 × 106 Da with the optimum polymerization conditions as follows: monomer concentration of 30%, monomer mass ratio m(AM) : m(DMC) of 3 : 1, initiator concentration of 0.6‰, illumination time of 80 min, solution pH value of 4.5, and incident light intensity of 1000 μW cm−2. The PAD was represented by several instruments. The results of FTIR and 1H NMR showed that PAD was indeed polymerized by AM and DMC. The results of TGA showed that PAD was very stable at room temperature while the result of SEM revealed that PAD had a porous structure and rough surface. For PAD used as flocculant in kaolin wastewater treatment, the results confirmed that, at optimal conditions, the turbidity and the floc size d50 could reach to 5.9 NTU and 565.936 μm, respectively, at the optimal conditions (pH = 7.0 and dosage = 2 mg l−1). Kaolin wastewater flocculation test outcome reveals that the PAD with high cationic degree and intrinsic viscosity could boost the charge neutralization and bridging capability. Consequently, the result is an excellent flocculation performance of treating kaolin wastewater.

Evaluation a self-assembled anionic polyacrylamide flocculant for the treatment of hematite wastewater: Role of microblock structure

Abstract Self-assembly is able to control molecular structure of flocculants and improves their flocculation efficiency. In this study, template polymerization and ultrasonic initiation system attributed to the self-assembly of anionic polyacrylamide (TPAS-U) with a microblock structure using acrylamide (AM) and sodium p-styrene sulfonate (SSS) as monomers and poly (allylammonium chloride) (PAAC) as template. The functional groups and ordered microblock structure in TPAS-U were discovered via characterization analysis. Association constant (KM) manifested the self-assembly mechanism. And the role of ultrasonic in the synthesis was discussed as well. TPAS-U with well-organized/special structure had excellent flocculation performance in the treatment of hematite wastewater over other anionic flocculants. The flocs formed by TPAS-U possessed the big size, the compact structure and the strong recover ability after breakage. The uniform and regular microblock structure in TPAS-U attributed to the high utilization efficiency of negative charges, which improved neutralization, adsorption and bridging in the treatment.

Using ultrasonic (US)-initiated template copolymerization for preparation of an enhanced cationic polyacrylamide (CPAM) and its application in sludge dewatering

In this study, the ultrasonic (US)-initiated template copolymerization was employed to synthesize a novel cationic polyacrylamide (CPAM) characterized by a microblock structure using dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomers, and sodium polyacrylate (NaPAA) as template. The polymers structure property was analyzed by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance spectroscopy (1H NMR) and thermogravimetric analysis (TGA). The results showed that a novel cationic microblock structure was successfully synthesized in the template copolymer of DMDAAC and AM (TPADM). Meanwhile, the analysis result of association constant (MK) provided powerful support for a I Zip-up (ZIP) template polymerization mechanism and the formation of the microblock structure. The factors affecting the polymerization were investigated, including ultrasonic power, ultrasonic time, monomer concentration, initiator concentration, mAM:mDMDAAC and nNaPAA:nDMDAAC. The sludge dewatering performance of the polymers was evaluated in terms of specific resistance to filtration (SRF), filter cake moisture content (FCMC), floc size (d50) and fractal dimension (Df). Flocculation mechanism was also analyzed and discussed. The sludge dewatering results revealed that the polymer with the novel microblock structure showed a more excellent flocculation performance than those with randomly distributed cationic units. A desirable flocculation performance with a SRF of 4.5 × 1012 m kg−1, FCMC of 73.1%, d50 of 439.156 µm and Df of 1.490 were obtained at pH of 7.0, dosage of 40 mg L−1 and the molecular weight of 5.0 × 106 Da. The cationic microblock extremely enhanced the polymer charge neutralization and bridging ability, thus obtaining the excellent sludge dewatering performance.

The investigation of the specific behavior of a cationic block structure and its excellent flocculation performance in high-turbidity water treatment.

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment. This study introduced an ultrasound (US)-initiated template polymerization (UTP) method to develop a novel cationic templated polyacrylamide (TPAA) with a microblock structure. TPAA was prepared using acrylamide (AM) and sodium (3-acrylamidopropyl)trimethylammonium chloride (ATAC) as the monomers and sodium polyacrylate (NaPAA) as the template. Factors that affected polymerization such as the ultrasound power, ultrasound time, initiator concentration, pH, and mAM : mATAC and nNaPAA : nATAC values were investigated. The properties of the polymers were characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicated the successful formation of a cationic microblock structure in TPAA. In addition, TPAA displayed favorable thermal decomposition properties and a rough and coarse surface morphology, as shown by analyses using TGA and SEM, respectively. Moreover, a zip (type I) template polymerization mechanism was identified via analyses of the association constant (KM), conversion (Cv) and polymerization rate (Rp). The flocculation performance of the templated copolymer TPAA was evaluated by treating high-turbidity water. According to the results for the zeta potentials and FTIR spectra of the generated flocs, it was indicated that the cationic microblocks in the templated copolymer could greatly enhance its charge neutralization, patching and bridging ability, and therefore excellent flocculation performance (residual turbidity: 5.8 NTU, Df: 1.89, floc size d50: 608.404 μm and floc kinetic: 15.86 × 10−4 s−1) for treating high-turbidity water was achieved.

Preparation of cationic konjac glucomannan in NaOH/urea aqueous solution

Cationic derivatives of konjac glucomannan (KGM) were homogeneously synthesized by reacting KGM with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) in NaOH/urea aqueous solutions. The derivatives were characterized by FT-IR, 1H NMR, elemental analysis, thermogravimetric analysis and zeta potential analysis. The results showed that the degree of substitution (DS) of the CKGM with the value of 0.15–0.46 could be obtained by changing the molar ratio between KGM and CHPTAC. The TG/DTG revealed that the thermal stability of KGM after cationization was lower than that of raw KGM. Among a wide range of pH value, the zeta potential in CKGM solution was shown with positive charges. The flocculation capacity of the CKGM was assessed through Kaolin suspension using the light transmission test. The results exhibited that the CKGM had excellent flocculation performance and could be used as an emerging flocculant agent in the wastewater treatment.

Polyacrylamide grafted cellulose as an eco-friendly flocculant: Efficient removal of organic dye from aqueous solution

The efficient and safe flocculation of colored wastewaters from textile and leather industries is of great significance for natural environment and human health. In this work, an eco-friendly bamboo pulp cellulose grafting ployacrylamide (BPC-g-PAM) flocculant was synthesized and employed to remove organic dyes from dye solutions by flocculation. The flocculation performance of the synthesized BPC-g-PAM was evaluated by chroma and turbidity removals of a series of cationic and disperse dye solutions. A L9(34) orthogonal experiment was designed to optimize the flocculation process of the BPC-g-PAM. The positive results showed that, the BPC-g-PAM exhibited an excellent flocculation performance to organic dye solutions. The average decolorization rate reached 96.7 % and the chroma could be reduced to 5° or even lower for the disperse dye solutions. The mechanism of the BPC-g-PAM flocculation to disperse dyes was investigated and determined as chemical adsorption kinetics. Furthermore, the eco-friendly BPC-g-PAM also held an excellent biodegradability of 66.5 % at 45 d and 67.6 % at 90 d in soil extracting solution, which were far higher than the corresponding data of the commercial PAM.

Flocculation performance and mechanism of chitosan-based flocculants in the treatment of emulsified oily wastewater

ABSTRACTChitosan (CS)-based flocculants, denoted as CS-g-PAM and CS-g-PDBC, were successfully prepared via graft copolymerization of CS with acrylamide (AM) or dimethyl acryloyloxyethyl benzyl ammonium chloride (DBC). The grafting was confirmed by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). The flocculation performance of CS-g-PAM and CS-g-PDBC, as well as flocculants such as cationic polyacrylamide (CPAM), polyaluminum chloride (PAC), and CS, was evaluated and compared for treating emulsified oil wastewater. It was found that CS-g-PDBC exhibited excellent flocculation performance under both acidic and neutral conditions, while CS showed better flocculation ability under alkaline condition. The flocculation mechanism of CS and CS-g-PDBC was investigated via zeta potential measurements. Results showed that different flocculation mechanisms were involved at various pH levels. As regarding CS, the flocculation mechanism is mainly charge neutralization, patching, and sweep floc under acidic, neutral, and alkaline conditions, respectively, while for CS-g-PDBC, patching was the dominant mechanism under both acidic and neutral conditions.

2,3,6-Tricarboxylate Cellulose as a Fully Biodegradable Flocculant: Efficient Synthesis and Flocculation Performance

Cellulose-based flocculants have shown excellent performance for wastewater flocculation, being low-cost and eco-friendly. However, they are still disturbed by the problems of incomplete biodegradability and unstable chemical structure. In the present study, 2,3,6-tricarboxylate cellulose (TCC) was developed as a novel fully biodegradable flocculant to deal with the preceding problems. The key carboxymethylation of cellulose was first carried out to make the subsequent NaIO4 oxidation occur under homogeneous conditions, which greatly enhanced the carboxylate content of the final TCC products. The chemical structure and solution properties of the TCCs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer system (XRD), field emission scanning electron microscopy (FESEM), charge density, particle size, and zeta potential. The flocculation performance of the TCCs was evaluated preliminarily by the turbidity removal of kaolin suspension. The positive results showed that all the TCC products had high carboxylate contents (more than 10 mmol/g) and zeta potentials. They exhibited excellent flocculation performance for the kaolin suspensions, in which the residual turbidities decreased from 610 to 14.9 NTU. Considering the degradation of cellulose caused by excessive NaIO4 oxidation, the TCC IV, together with its synthesis technology, could be used for practical applications in wastewater flocculation.