Microblock Structure Research Articles

Evaluation an anionic polyacrylamide flocculant with microblock structure in the hematite wastewater treatment: Characterization and flocculation performance

In this study, a template polymer with anionic microblock structure was successfully synthesized through ultrasonic initiated template copolymerization (USTP) by using sodium allylsulfonate (SAS) and acrylamide (AM) as monomers, poly diallyl dimethyl ammonium chloride (polyDADMAC) as template, and 2,2′-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as initiator. The anionic polyacrylamide (APAM-T) flocculant was characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), and scanning electron microscopy (SEM). Furthermore, the X-ray photoelectron spectroscopy (XPS) was conducted to measure the elemental composition. The results of XPS and 1H NMR spectroscopy analysis indicated the existence of anionic microblock structure in APAM-T. Besides, the copolymerization was revealed to follow the self-assembly mechanism by analyzing the association constant (KM). The flocculation performance was evaluated by turbidity and zeta potential in the flocculation tests. The results indicated that the APAM-T with microblock structure enhanced the charge neutralization and bridging adsorption capacity, thus improving the flocculation performance. In the floc particle size distribution and fragmentation and reflocculation experiments, the floc corresponding to APAM-T had the strongest regeneration ability after fragmentation, which further confirmed the criticality of the microblock structure in enhancing the flocculation performance. Compared with existing studies, this study not only demonstrated a novel synthesis method, but also found that the microblock structure could significantly improve its treatment efficiency and effectiveness, providing a new theoretical basis and practical application path for wastewater treatment technology.

Design and Synthesis of Comb‐Like Bisulfonic Acid Proton Exchange Membrane with Regulated Microstructure

AbstractThe design and synthesis of proton exchange membranes (PEMs) with controllable microstructure and sulfonation degree play a crucial role in enhancing their performance and expanding their application. In this study, the disulfonic acid monomer is designed and prepared to synthesize the comb‐like disulfonic PEMs with controllable ion exchange capacity. The results show that the side chain structure and more concentrated sulfonic acid groups facilitate the aggregation of sulfonic acid groups in the polymer, improve the microphase separation morphology of PEMs, and increase the ionic conductivity. The proton conductivity of the DS‐PXIDI‐60 membrane is approximately 300 mS cm−1. The PEMs with controllable microstructure are prepared by introducing comonomers, including 9,9‐dimethylxanthrene, biphenyl, and p‐terphenyl, with different reactivity, spatial structure, and solubility. Biphenyl is copolymerized to form a copolymer with an alternating structure, and 9, 9‐dimethylxanthrene is copolymerized to form a random copolymer. In addition, it is worth noting that p‐terphenyl is copolymerized to form a microblock structure of the copolymer, with more excellent comprehensive properties. DS‐PXITp‐60 exhibits better performance than Nafion 212 in redox­flow batteries and fuel cells. Therefore, such molecular design and synthesis strategies provide a reference guide for the development of high‐performance PEMs.

Preparation of cationic polyacrylate W/O crude oil emulsion demulsifier by free‐radical solution polymerization

AbstractThe block polyether demulsifier prepared by ring‐opening polymerization of ethylene oxide and propylene oxide under high temperature and high pressure is the most widely used demulsifier for water in crude oil emulsion. It has the high synthesis risk and cost. Therefore, the development of non‐block polyether demulsifier has attracted more and more attention. In this article, a new type of demulsifier was sythesized by radical polymerization of acrylate and cationic monomer. It was found that the copolymer PMA‐co‐PDBC of methyl acrylate (MA) and benzyldimethyl [2‐[(1‐oxoallyl)oxy] ethyl] ammonium chloride (DBC) synthesized in the mixed solvent of dipropylene glycol methyl ether and water had a good performance. When dosage of PMA‐co‐PDBC was 200 mg/L, the dehydration rate of water in crude oil emulsion with 50% water content can reach 80% at 80°C within 4 h. Structural and interface properties analysis presented that PMA‐co‐PDBC had a microblock structure similar with block polyether and it can effectively reduce the strength of W/O interfacial film to realize the demulsification. Although the demulsification performance of PMA‐co‐PDBC was not better than block polyether, its preparation safety and cost are much better. The results of this article can provide a new option for the development of crude oil demulsifier.

Preparation of amphiphilic cationic polyacrylamide (CPAM) with cationic microblock structure to enhance printing and dyeing sludge dewatering and condition performance.

Flocculation is an important pretreatment technology for sludge dewatering, and the flocculant's performance is the key factor to determine the flocculation effect. Cationic polyacrylamide (CPAM) is commonly used in dewatering and conditioning of printing and dyeing sludge (PD sludge), and the research of high-efficiency flocculant is a hot spot in the field of PD sludge dewatering. Hydrophobic butylacrylate (BA) and (2-(Methacryloyloxy)ethyl) trimethylammonium chloride (DMC) were introduced into the copolymer, and amphiphilic (hydrophilic/lipophilic) CPAM, namely TP-ADB, with microblock structure was synthesized by ultrasonic initiated template copolymerization in this study. The functional group composition of TP-ADB was determined by FTIR and 1H NMR. Thermogravimetric analysis (TGA) showed that TP-ADB had good thermal stability. The amphiphilic rheological properties of the copolymer were measured according to the apparent viscosity. In addition, 1H NMR and TGA results confirmed the existence of microblock structure in the copolymer chain. The polymerization mechanism was discussed by association coefficient (KM) measurement. The results showed that the template copolymerization initiated by ultrasonic followed the law of free radical copolymerization. The pre-adsorption of DMC with sodium polyacrylate template (NaPAA) before the reaction confirmed that the template polymerization accorded with ZIP I mechanism. The cationic microblock structure and hydrophobic association of TP-ADB promoted the dewatering performance of PD sludge (FCMC = 72.9%, turbidity removal rate = 98.9%, SRF = 4.2 × 1012m·kg-1). Hydrophobic association enhanced the bridging, sweeping, and net catching effect, and promoted the growth of floc size and fractal dimension. Cationic microblock structure can produce compact floc with higher mechanical strength by enhancing electrical neutralization and electrical patching. As a skeleton, the compressibility of filter cake was reduced and the permeability was enhanced, and the PD sludge dewatering effect was significantly improved.

Research on a new cationic polyacrylamide (CPAM) with a cationic microblock structure and its enhanced effect on sludge condition and dewatering.

Flocculation is one of the commonly used sludge conditioning methods in water supply plants, which can improve the sludge dewatering performance by reducing the specific resistance of sludge (SRF), decreasing the amount of sludge, and finally lowering the transportation cost and subsequent disposal cost of sludge. Therefore, it is particularly important to develop new and efficient flocculants. In this paper, the template copolymer of acryloxy trimethylammonium chloride (DAC) and acrylamide (AM) was successfully synthesized by microwave-template copolymerization (MV-TP) using sodium polyacrylate (NaPAA) as template. The template copolymer was analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and scanning electron microscopy (SEM). It was found that this template copolymer had obvious cationic microblock structure. In addition, the test results of association constant (KM) and polymerization kinetics showed that the MW-TP was assigned to free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP). It confirmed the formation of cation fragment structure again. Due to its dense positive charges in this new cationic microblock structure, it greatly improved the functions of electric neutralization, electrical patching, and adsorption bridging. The cationic fragment structure in the template copolymer could help to generate large and dense floc structure and form stable drainage channels. Under external pressure, these large and compact floc structures had greater compressive resistance, which avoided deformation and blockage of drainage channels and voids. It was beneficial to reduce SRF and evidently enhanced sludge dewatering performance.

Combination of bacitracin-based flocculant and surface enhanced Raman scattering labels for flocculation, identification and sterilization of multiple bacteria in water treatment

Bacteria, especially antibiotic-resistant bacteria, in water threaten public health in countries. Simultaneous flocculation, sterilization and identification of bacteria are great challenge in water treatment. Herein we presented a three-in-one compound through combining a novel Bacitracin-based flocculant (B-g-PAMDAC) and surface enhanced Raman scattering (SERS) labels, the modified Au@AgNPs using graphene oxide (GO) and 4-mercaptophenylboronic acid (4-MPBA). B-g-PAMDAC with bactericidal groups and microblock structure was synthesized via copolymerization and self-assembly. Its functional groups and microblock structure contributed to the excellent performance in flocculation of bacteria. 4-MPBA as bacterial capture bound to the bacterial cell membrane and contributed to recognition of bacteria in flocculation. Bacteria aggregating around Au@AgNPs resulted in abundant “hot spots” and strong Raman signals. SERS labels obviously improved the sensitivity, accuracy and stability of bacteria identification even at low bacterial concentration of 1 × 103 CFU mL−1. They presented distinct fingerprints of bacteria, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus and Enterococcus faecalis, in Raman mappings. Bacitracin improved sterilization efficiency of B-g-PAMDAC in four bacteria treatment in terms of sterilization rate and time. β-galactosidase and respiratory activity of bacteria revealed sterilization mechanism of B-g-PAMDAC that changed permeability of cell membrane before it reduced the respiration activity of bacteria and ruptured cell wall.

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.

Enhanced municipal sludge dewaterability using an amphiphilic microblocked cationic polyacrylamide synthesized through ultrasonic-initiation: Copolymerization and flocculation mechanisms

Flocculation is an important pretreatment technique for sludge dewatering, the performance of employed flocculants is the key factor determine the flocculation efficiency. Herein, an amphiphilic cationic polyacrylamide (CPAM) with microblock structure was synthesized through template copolymerization initiated by ultrasonic. The chemical components and cationic microblock structure of copolymers were confirmed through comparative characterization by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (1H NMR) spectrum. The copolymerization mechanism was investigated through kinetics study and association coefficient (KM) determination. The results indicated that the reaction followed free radical copolymerization and terminated mainly through bimolecular termination. The pre-adsorption between acryloyloxyethyltrimethylammonium chloride (DAC) and sodium polyacrylate (NaPAA) before reaction confirmed the template polymerization met the type I (ZIP) mechanism. Cationic microblocks and hydrophobic association together contributed to the optimal dewaterability (FCMC=67.2 %, SRF=3.84×1012 m·kg−1) using TP(AM-DAC-LA). Hydrophobic association enhanced bridging and sweeping effect to promote the floc size growth. Cationic microblocks produced compacter flocs with stronger mechanical strength through enhanced charge neutralization and patching effects, which acted as skeletons to make filter cakes less compressible and more permeable in mechanical dewatering. This work developed a highly effective flocculant for sludge dewatering, the synthesis and working mechanism of which were also given.

Magnetic Template Anion Polyacrylamide-Polydopamine-Fe3O4 Combined with Ultraviolet/H2O2 for the Rapid Enrichment and Degradation of Diclofenac Sodium from Aqueous Environment.

In this study, a novel system was set up by preparing a magnetic flocculant combining with ultraviolet/H2O2 to realize the rapid enrichment and degradation of diclofenac sodium (DCFS). For the magnetic flocculant, template anion polyacrylamide (TAPAM) with anion micro-block structure was prepared. Thereafter, polydopamine was used to modify TAPAM, Fe3O4 nanoparticles was grafted to the modified TAPAM by chelation, named template anion polyacrylamide-polydopamine-Fe3O4 (TAPAM-PDA-Fe3O4). Furthermore, the TAPAM-PDA-Fe3O4 preparation protocol was optimized by the response surface method (RSM). In the DCFS enrichment section, the rapid separation of flocs from water was realized by an external magnetic field and it indicated that the π–π stacking effect was dominant in neutral/alkaline condition, whereas charge neutralization was favored in acidic conditions. Meanwhile, a DCFS enrichment kinetic curve was much fitted by the pseudo-second-order kinetic model and DCFS enrichment isothermal curve was close to the Freundlich isothermal model, indicating the dependence of DCFS quantity enriched by TAPAM-PDA-Fe3O4 and a multilayer heterogeneous enrichment process. The degradation experiment confirmed that DCFS was effectively degraded by ultraviolet/H2O2/TAPAM-PDA-Fe3O4 and the maximum value of DCFS degradation efficiency reached 98.1%. Furthermore, the regeneration experiment showed that the enrichment and degradation efficiency of DCFS could maintain a relatively high level in the initial three recycles.

MICRO-BLOCK STRUCTURE OF THE GEOLOGICAL ENVIRONMENT AS A FACTOR OF THE GEOLOGICAL RISKS FOR URBAN TERRITORIES

Problem Statement and Purpose. Geological risks are the specific risks at buildings construction and operation; those risks influence decision-making connected with building, reconstruction, development of protection schemes and pre-investment feasibility studies. The results of studies performed during recent decades have shown that significant role in buildings and constructions deformation, forming and dynamics of landslide processes and peculiarities of groundwater regime is played by inhomogeneity of geological environment expressed through its hierarchical and block (including micro-block) structure. The paper aims at engineering & geodynamical assessment of the territory of Odessa Infectious Diseases Hospital and identification of the sites of potential geological risk connected with inter-block zones. We also plan to justify statement that geodynamic factor is one of geological risk key factors during designing and operation of buildings and constructions.Data & Methods. Data from geological drilling (stratigraphic affiliation, lithology, absolute layer elevations отметки слоев, groundwater layers) of 83 boreholes and instrumental measurements of technological tunnel constructive elements’ deformation and displacement collected during 40 years long operation period (1970-2011) have been used to study the main structural and tectonic features of the Infectious Diseases Hospital area. Cartographic modeling based on the gradient zones found (i.e. the zones within which abnormally quick changing of geological surfaces elevation marks was revealed in this or that direction) has been used as the method to determine the highest geological risk zones. As is known, such zones are the indicators of differential movement of different scale geoblocks, including the smallest ones having typical size of dozens of meters. Maps of gradients of relief of the top of plastic sand and clay Meotain depositions and «fragile» pontic limestones have been built. To reveal spatial periodicity of deformation and displacement of the technological tunnel constructive elements spectrum and harmonic analysis (Fourier transform) has been done. Statistical and cartographic analysis of the above datasets was done according to traditional methodologies realized in the software Statistica, Matlab and Surfer.Results. Based on engineering & geodynamical analysis (geo-historical studies, geological data and instrumental measurements) disjunctive dislocations forming hierarchical and block structure of geological environment of Odessa Infectious Diseases Hospital and being the zones of increased engineering & geodynamical risks were revealed. It is shown that key role in the strategy of geological risks studying should be played by structural & tectonic factor. The regularities identified at the territory of the city Infectious Diseases Hospital are typical of the entire Odessa region and show that significant role at engineering & geological assessment of the city area is played by micro-block structure of geological environment whose main elements are inter-block zones. Extreme gradients of speed and deformation caused by differentiated character of blocks movement are typical of such zones; the zones can lead to selective destruction of buildings, constructions and communications, and be a prerequisite to decrease of slopes stability. The methodological complex proposed can be used successfully in many urban regions for identification of the sites of potential geological risk connected with inter-block zones.

Hydrophobic modification of cationic microblocked polyacrylamide and its enhanced flocculation performance for oily wastewater treatment

In this study, a novel amphiphilic flocculant TP-ADL was synthesized using acrylamide, methacryloxyethyltrimethyl ammonium chloride and lauryl acrylate as monomers through UV-light-initiating template copolymerization technology. Copolymerization conditions were optimized towards higher intrinsic viscosity and conversion rate. The Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy (NMR) analysis confirms the functional groups composition in TP-ADL, and the thermogravimetric (TGA) analysis indicates its good thermal stability. Furthermore, the detailed 1H NMR and TGA analysis confirms the microblock structure in polymer chain. The amphiphilic rheological characteristics of copolymer were detected according to apparent viscosity. TP-ADL displayed superior flocculation efficiency towards oily wastewater in terms of oil and turbidity removal rate, and zeta potential. The median floc size (d50) and fractal dimension (Df) results indicate a large and compact floc structure. The synergistic effect between cationic microblock structure and inter-molecular hydrophobic association is the main reason for the better treatment efficiency.

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.

Effect of cationic polyacrylamide with cationic microblock structure on dual-flocculant sludge conditioning: performance and mechanism

Effect of cationic polyacrylamide with cationic microblock structure on dual-flocculant sludge conditioning: performance and mechanism

Ultrasound-initiated synthesis of cationic polyacrylamide for oily wastewater treatment: Enhanced interaction between the flocculant and contaminants

Weak interaction between flocculants and oil is a main bottleneck in the treatment of oil-containing wastewater. To solve this problem, a novel flocculant PAB with cationic micro-block structure and hydrophobic groups of benzene rings was synthesized by ultrasound initiated polymerization technique and applied to remove turbidity and oil from water. To avoid unnecessary addition of reagents in traditional template and micellar copolymerization, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) with self-assembly ability in aqueous solution was employed to synthesize flocculants. The critical association concentration of BMDAC measured by conductivity and surface tension methods was 0.014 mol·L−1. The results of reactivity ratio, statistical analysis of sequence-length distribution and 1H NMR provided evidence for the synthesis of copolymer with cationic micro-block. In addition, the apparent viscosity measurement indicated that PAB had an obvious hydrophobic association property. Finally, flocculation tests demonstrated that flocculation performance was greatly improved by adding PAB and the removal rate of oil and turbidity both reached the maximum (87.5% and 92%) at dosage of 40 mg·L−1 and pH of 7.0. Flocculation mechanism investigation demonstrated that the cooperation of charge neutralization, adsorption bridging, and hydrophobic association effect played an important role. The formed flocs by PAB was large, compact, difficult to break, and easy to regrow because of the enhanced interaction between flocculants and oil. In summary, this study can provide important reference in the design of organic flocculants in oily wastewater treatment applications.

Effect of the Cationic Block Structure on the Characteristics of Sludge Flocs Formed by Charge Neutralization and Patching.

In this study, a template copolymer (TPAA) of (3-Acrylamidopropyl) trimethylammonium chloride (AATPAC) and acrylamide (AM) was successfully synthesized though ultrasonic-initiated template copolymerization (UTP), using sodium polyacrylate (PAAS) as a template. TPAA was characterized by an evident cationic microblock structure which was observed through the analyses of the reactivity ratio, Fourier transform infrared spectroscopy (FTIR), 1H (13C) nuclear magnetic resonance spectroscopy (1H (13C) NMR), and thermogravimetry/differential scanning calorimetry (TG/DSC). The introduction of the template could improve the monomer (AATPAC) reactivity ratio and increase the length and amount of AATPAC segments. This novel cationic microblock structure extremely enhanced the ability of charge neutralization, patching, and bridging, thus improving the activated sludge flocculation performance. The experiments of floc formation, breakage, and regrowth revealed that the cationic microblock structure in the copolymer resulted in large and compact flocs, and these flocs had a rapid regrowth when broken. Finally, the larger and more compact flocs contributed to the formation of more channels and voids, and therefore the specific resistance to filtration (SRF) reached a minimum.

Improvement of Sludge Dewaterability by Ultrasound-Initiated Cationic Polyacrylamide with Microblock Structure: The Role of Surface-Active Monomers

Cationic polyacrylamides have been employed widely to improve sludge dewatering performance, but the cationic units are randomly distributed in the molecular chain, which restricts the further enhancement of dewaterability. Common template technology to prepare block copolymers requiring a huge number of templates reduces the polymer purity and molecular weight. Here, we adopted the surface-active monomer benzyl dimethyl 2-(methacryloyloxy)ethyl ammonium chloride (BDMDAC) to synthesize cationic microblocky polyacrylamide initiated by ultrasound. The reactivity ratio of monomers suggested that novel cationic monomer BDMDAC had higher homopolymerization ability, and was thus more prone to forming a microblock structure. The statistical analysis of sequence-length distribution indicated that the number and length of cationic segments increased in the PAB molecules. In addition, the characteristic results of Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA) provided evidence for the synthesis of copolymer with cationic microblocks. Finally, the results of dewatering tests demonstrated that sludge dewaterability was greatly improved by adding the synthesized novel flocculants, and the sludge-specific resistance to filtration, filter cake moisture content and residual turbidity all reached a minimum (68.7%, 5.4 × 1012 m·kg−1, and 2.6 NTU, respectively) at 40 mg·L−1. The PAB flocs were large, compact, difficult to break, and easy to regrow. Furthermore, PAB was more effective in the removal of protein from soluble extracellular polymeric substances (SEPSs). In summary, this study provides a novel solution to synthesize cationic microblock polyacrylamide for improving sludge dewatering.

Synthesis, Characterization, and Solution Behavior of a Long-Chain Hydrophobic Association Anionic Acrylamide/2-Acrylamido-2-Methylpropanesulfonic Acid/n-Octyl Acrylate Terpolymers

A long-chain hydrophobic association anionic terpolymer (PAAO) was synthesized by acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and n-octyl acrylate using the micellar polymerization technique to obtain an oil-displacement polymer with good thermal stability and solution properties. The molecular structure of the terpolymer was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Conventional thermogravimetric analysis measurement was used successfully to characterize the hydrophobic microblock structure of PAAO. The initial decomposition temperature of the polymer was 222 \(^{\circ }\hbox {C}\), higher than that of polyacrylamide \((210\,^{\circ }\hbox {C})\). As indicators of enhanced oil recovery (EOR) technology, polymer concentration, salinity tolerance, temperature, and shear rate were investigated in the aqueous solution. The number of hydrophobic monomers strongly affected the apparent viscosity behaviors of the polymers. PAAO exhibited favorable viscosity enhancement properties, salt tolerance, temperature resistance, and recoverable viscosity after shearing, making it useful in EOR and drilling fluids.

Enhancement of textile-dyeing sludge dewaterability using a novel cationic polyacrylamide: role of cationic block structures

A novel cationic polyacrylamide (CPAM) with a microblock structure was synthesized through ultrasonic-initiated template copolymerization (UTP) using allyltrimethylammonium chloride (TM) and acrylamide (AM) as monomers, and sodium polyacrylate (NaPAA) as a template.