Composite Flocculant Research Articles

Design of SiO2-TiO2-P(AM-DMC) cationic composite flocculant and optimization of the flocculation process using response surface methodology

At present, the polymer flocculation technology has been widely used in the treatment of oil sand tailings. However, the current composite flocculant still has the problems of low flocculation efficiency and serious secondary pollution after using. In this article, cationic composite flocculant SiO2-TiO2-P(AM-DMC) with self-degrading characteristics was prepared by the surface photoinitiated polymerization technique. Above all, in order to study the synthesis process of SiO2-TiO2-P(AM-DMC), cationic composite flocculant was characterized by FTIR, TG, TEM, XPS, etc. Furthermore, the central composite design (CCD) and response surface methodology (RSM) were used to optimize the preparation parameters of the cationic composite flocculant. And the optimization results of preparation parameters of cationic composite flocculant showed that the optimal preparation parameters of SiO2-TiO2-P(AM-DMC) were as follows: m DMC: m AM = 5, monomer concentration was 35% and reaction time was 100 min. Ultimately, the flocculation parameters of SiO2-TiO2-P(AM-DMC) were optimized by CCD and RSM. Moreover, the optimization results of flocculation parameters of cationic composite flocculant showed that the optimal flocculation parameters of SiO2-TiO2-P(AM-DMC) were as follows: pH = 5, flocculant dosage was 30 ppm, kaolin concentration was 1.36%. In summary, this work had greatly enriched the knowledge of oil sand tailings treatment, and had the extremely important reference significance for realizing the parameter regulation of high-efficiency flocculation of oil sand tailings.

Impacts of composite flocculant in coagulation/ultrafiltration hybrid process for treatment of humic acid water: the role of basicity

ABSTRACT The effects of the composite flocculant, polyaluminium chloride and poly dimethyldiallylammonium chloride (PACl-PDMDAAC) in comparison with PACl on coagulation efficiencies and membrane fouling in coagulation-ultrafiltration (C-UF) process were analysed, which was conducted in the conditions of different basicity (B) values and the presence of Mg2+. Results showed that PACl-PDMDAAC enhanced the ability of charge neutralization and absorption bridging, and improved the coagulation efficiency. When B value was 1.5, the flocculant hydrolyzed to form more Alb morphology and effectively removed HA molecules. The presence of Mg2+ could improve the coagulation performance through bridging ability. The results of the ultrafiltration test showed that the flux reduction for PACl was 70%, while the flux reduction for PACl-PDMDAAC was 60% in C-UF process. PACl-PDMDAAC could effectively reduce membrane fouling mainly by reducing strongly attached cake/gel layer. When B value was 1.5, the Alb content of the flocculant was higher and the ability of adsorption charge neutralization was strong, resulting in forming a stable cake layer. Therefore, the membrane fouling was the lightest. In addition, the presence of Mg2+ in raw water reduced the membrane fouling.

Preparation of a novel inorganic-biological composite flocculant for the removal of turbidity and organic matter in the surface water

Preparation of a novel inorganic-biological composite flocculant for the removal of turbidity and organic matter in the surface water

A kaolinite-based design of kaolin/TiO2–PAM composite flocculant and the application of the oil sand tailings flocculant

We prepared an efficient kaolin–TiO2–polyacrylamide (PAM) organic–inorganic composite flocculant; the synthesis process is simple and suitable for mass industrial production. First, the surface of kaolin was modified with titanium dioxide, and then the acrylamide monomer was initiated on the surface by a surface-initiated polymerization method; thus, the PAM polymer was successfully grown on the surface of kaolin, thereby effectively improving the water-reducing efficiency. Utilizing good adsorption properties for impurities of kaolin itself and via regulation of the degree of polymerization of the PAM polymer, the cost could be effectively reduced and the water-reducing efficiency could be improved. Further, the microstructure and morphology were observed by scanning electron microscope and transmission electron microscopy, and elemental analysis was carried out by X-ray photoelectron spectroscopy. The results showed that nano-titanium dioxide was successfully loaded onto the surface of kaolin and the surface of the composite particles was successfully coated with PAM. The functional groups before and after the synthesis of the material were characterized. Further confirmed that the surface of the composite ion was successfully coated with PAM. In addition, the thermodynamic stability of the prepared material was analyzed by thermogravimetry; the average PAM content was 53.7 wt%. Furthermore, from the flocculation experiment (tested with simulated oil sand tailings), it was found that the water-reducing rate of the kaolin–TiO2–PAM organic–inorganic flocculant toward the flocculation of oil sand tailings exceeded 85%, and the transmittance increase exceeded 94%. Finally, the flocculation behavior and flocculation mechanism of the kaolin–TiO2–PAM composites under different flocculant dosages and pH conditions were carefully studied.

Analysis of the Sedimentation Characteristics of Ultrafine Tailings Based on an Orthogonal Experiment

Due to continuous improvements in the beneficiation process, the size of tailings has decreased. In many mines, more than 50% of the total tailings are finer than 74 μm. Ultrafine tailings exhibit a slow settling velocity and uneven settling, which pose new challenges to the safety and stability of tailings dams. In this paper, ultrafine iron tailings from the Makeng Iron Mine in Longyan City, Fujian Province, were used as the research object. A four-factor, three-level orthogonal test method was used to study the sedimentation characteristics of ultrafine tailings with four common curing agent materials, including polyacrylamide, polyaluminum chloride, polyaluminum sulfate, and polyferric sulfate. The results show that when the pulp concentration is 30%, the polyacrylamide is cationic and the molecular weight is 10 million, the optimal content of the flocculant is 3‰, the optimum dose of the polyaluminum chloride with a content of 28 is 0.1‰, the optimum dose of polyaluminum sulfate is 1‰, and the optimum dose of polymeric ferric sulfate is 1‰. When the flocculant is mixed according to the proportion of 2‰ polyacrylamide, 0.05‰ polyaluminum chloride, 1‰ polyaluminum sulfate, and 1.0‰ polyferric sulfate, the sedimentation speed of the ultrafine tailings is fast, and the supernatant liquid is clear. The results of multivariate nonlinear regression analysis of the sedimentation curve show that the primary and secondary factors affecting sedimentation are polyacrylamide > polyaluminum sulfate > polyaluminum chloride > polyferric sulfate. When the optimal ratio is applied, the cohesion (c) of ultrafine tailings increases from 27 kPa to 68.75 kPa and the internal friction angle (φ) increases from 25.53° to 27.53°, which shows that the shear strength improves and the stability of the tailings dam increases. The economic analysis of the composite flocculant with the optimal ratio shows that the flocculant with the optimal proportion has an obvious economic advantage over polyacrylamide alone.

Magnetic flocculation of algae-laden raw water and removal of extracellular organic matter by using composite flocculant of Fe3O4/cationic polyacrylamide

Algae-laden water with low turbidity is a critical problem in eutrophic lakes of arid regions. Thus, how to effectively separate algae and turbidity is an urgent problem for drinking water production. In the current study, the magnetic flocculation performance of algae-laden raw water purification was investigated by using magnetic composite flocculant Fe3O4/cationic polyacrylamide (CPAM). The Chlamydomonas sp., turbidity and UV254 removal efficiency were evaluated at different Fe3O4: CPAM mass ratios, dosages and pH values. The recovery and reusability of Fe3O4/CPAM in flocculation was tested. Moreover, the saturation magnetization of flocculants and flocs and zeta potential of supernatant in magnetic separation was examined, and the flocculation mechanism of Chlamydomonas sp. was explored accordingly. In addition, the removal efficiency of bound extracellular organic matter (BEOM) and dissolved extracellular organic matter (DEOM) was compared by using Fe3O4/CPAM. The flocculation mechanism and interactions between Fe3O4/CPAM and extracellular organic matters were analyzed according to ultraviolet (UV) spectra, fluorescence three-dimensional excitation emission matrix spectra (EEM), gel permeation chromatography (GPC), and X-ray photo electronic spectroscopy (XPS). Results show that more than 97% of chlorophyll a (Chla), 87% of turbidity, and 65% of UV254 were removed at Fe3O4/CPAM dosage of 1.2 mg/L, Fe3O4: CPAM mass ratio of 1.5:1.0, and pH of 4.0–9.0. Charge neutralization was dominant at pH < 9.0, whereas adsorption through hydrogen bond played an important role at pH > 9.0. Humic acid-like substances and tryptophan-like proteins were the main components of DEOM, whereas fulvic acid-like substances, tryptophan-like proteins and few polysaccharides existed in BEOM. Fe3O4/CPAM exhibited excellent performance in binding with the functional groups in tryptophan-like proteins, such as amino, carboxyl and hydroxyl groups.

Evaluation of carboxymethylpullulan-AlCl3 as a coagulant for water treatment: A case study with kaolin.

A reduction in the use of aluminum (Al)-based flocculants in the treatment of drinking water is considered essential for human health reasons. In this study, a novel composite flocculant, made of carboxymethylpullulan-AlCl3 , is evaluated in a lab-scale, jar test system for the flocculation of kaolin. The results showed that the coagulation efficiency of carboxymethylpullulan-AlCl3 was more effective in reducing turbidity than the solo use of carboxymethylpullulan or AlCl3 . The optimum treatment conditions assessed by a response surface methodology were obtained at pH 6.50, 13.03mg/L carboxymethylpullulan, and 94.87mg/L AlCl3 . Zeta potential measurements and photometric dispersion analysis demonstrated that AlCl3 had a more significant influence on charge neutralization than carboxymethylpullulan, whilst carboxymethylpullulan facilitated absorption and the development of particle bridges. Thus, the composite flocculant possessed both advantages that enhanced flocculation, and decreased the dosage of AlCl3 , thereby reducing the potential for secondary environment pollution. When 90mg/L carboxymethylpullulan-AlCl3 was added to the model kaolin suspension characterized by a turbidity of 50 nephelometric turbidity units, the zeta potential and the maximum flocculating activity were determined as -2.28mV and 98.0%, respectively. The results provide insight into the development of an environment-friendly composite flocculant prepared from water-dissolved polysaccharide and inorganic flocculants. PRACTITIONER POINTS: A novel composite flocculant CMP-AlCl3 was achieved by combining CMP and AlCl3 for water treatment. The coagulation efficiency of CMP-AlCl3 was more effective in reducing turbidity than the solo use of CMP or AlCl3 . The flocculation efficiency and mechanism were investigated by Zeta potential analysis, surface morphology, electron microscopy, and coagulation.

Design of SiO2-TiO2-PAM composite flocculant with self-degrading characteristics and optimization of the flocculation process using a combination of central composite design and response surface methodology

Nowadays, the polymer flocculation technology has been widely used in the treatment of oil sand tailings pollutants. However, the most commonly used polyacrylamide flocculant has encountered some problems, such as low flocculation efficiency and severe secondary pollution. In this paper, an organic-inorganic composite high-efficiency flocculant with self-degradation was designed and prepared. Furthermore, in order to analyze the synthesis mechanism of the composite material, the functional groups of the material were investigated by Fourier transform infrared spectroscopy (FTIR). At the same time, the morphology and structure were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Meanwhile, the crystal structure was recorded by XRD. In addition, the flocculation efficiency of the composite flocculant was determined by measuring the turbidity removal of the kaolin suspension. Apart from this, the flocculation parameters were optimized by central composite design (CCD) experimental design and response surface methodology (RSM). Finally, the self-degrading property of the flocculant was tested under light conditions. The characterization data of the material indicated that the synthesis mechanism is that under the ultraviolet light condition, the acrylamide monomer undergoes free radical polymerization under the action of active free radicals on the surface of the core-shell structure SiO2-TiO2 to form an organic-inorganic composite flocculant. In addition, the optimized experimental results showed that the optimal turbidity removal conditions were followed: VTBOT/mSiO2 of 6.66 mL/g, flocculant dosage of 50 ppm and kaolin suspension concentration of 1.5 wt%. Ultimately, the degradation experiment showed that the prepared organic-inorganic composite flocculant has nice self-degradation performance, and the self-degradation efficiency reaches over 90% within two hours. In summary, this work has greatly enriched the knowledge of oil sand tailings treatment.

Cationic starch-grafted-cationic polyacrylamide based graphene oxide ternary composite flocculant for the enhanced flocculation of oil sludge suspension

In this study, a novel, highly efficient and environmentally friendly ternary composites flocculant, namely, cationic starch-grafted-cationic polyacrylamide/graphene oxide (CS-g-CPAM/GO), was synthesized by ammonium persulfate initiation polymerization and condensation reaction. First, CS-g-CPAM was polymerized with cationic starch (CS), acrylamide (AM) and diallyl dimethyl ammonium chloride (DMDAAC), and CS-g-CPAM/GO was then synthesized by condensation reaction. The influence factors of graft polymerization were investigated, including total monomer concentration, initiator dosage, monomer mass ratio of mAM: mCS: mDMDAAC, post-polymerization temperature and post-polymerization time. The chemical structures and morphologies of the samples were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The CS-g-CPAM/GO was used to flocculate the oil sludge suspension, the effects of CS-g-CPAM/GO dosage, temperature and pH value on the flocculation performance were investigated, and the flocculation mechanism of CS-g-CPAM/GO was also analyzed. The results show that CS-g-CPAM/GO has outstanding flocculation effect, and CS-g-CPAM/GO flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.

Research on self-degradation of RGO/TiO2-P(AM-DAC) organic-inorganic composite flocculant prepared by surface initiated polymerization and its flocculation mechanism of oil sand tailings

In recent years, compared to commercial flocculants, organic-inorganic composite flocculants exhibit unique advantages in the field of oil sand tail flocculation, instilling technical strength of the new era into the traditional petrochemical industry. However, there are also defects in organic-inorganic composite flocculants, such as insufficient adsorption of tailings particles by polymers, and weak interface bonding between inorganic particles and polymers. In addition, the residual macromolecule in the solution after flocculation causes serious harm to the environment. In order to solve the above problems, the free radicals generated by RGO/TiO2 inorganic particles under illumination are used to initiate the copolymerization of AM and DAC monomers, which enables the copolymer P(AM-DAC) to grow in situ on the surface of inorganic particles, thereby preparing organic-inorganic composite flocculant that is closely bonded at the interfaces and able to electrostatically adsorb oil sand tailings particles. In this paper, the structure of the product is characterized by infrared spectrum, thermal analysis and XPS. The bonding of organic and inorganic interfaces is observed by TEM. The zeta potential is used to study the charged properties of the material. In addition, the simulated oil sand tailings are used to evaluate the effect of the proportion of cationic monomer on the flocculation, and the self-degradation performance of the material is tested under illumination as well as the degradation mechanism is analyzed by infrared spectroscopy with different illumination time. The results found that method can copolymerize both monomers in situ on the surface of the inorganic particles to form a copolymer and the organic-inorganic two-phase interface is tightly combined. The introduction of the cationic monomer (DAC) increases the flocculant cationicity and zeta potential. When the content of the cations is 30%, the flocculation effect reaches the highest. The photo-degradation test shows that the RGO/TiO2-P(AM-DAC) flocculant is capable of self-degradation under illumination conditions. After 8 h of illumination, the degradation rate is 26.1%. The work provides a theoretical basis and technical prototype for the development of polymerization technology and the design of a new generation of dedicated flocculant for oil sand tailings.

Design and preparation of flocculant with self-degrading characteristics for dewatering of oil sand tailings

Polymer flocculation technology is widely used in the treatment of oil sand tailings pollutants. However, the most commonly used polyacrylamide flocculants have problems of secondary pollution. In this paper, under ultraviolet light, the composite was prepared by photoinitiated precipitation polymerization of acrylamide on the surface of nano TiO2, providing a facile strategy for the synthesis of organic-inorganic hybrid flocculants. A series of organic-inorganic hybrid materials with different light sources, UV irradiation times, TiO2 contents and AM contents were synthesized, and connected by covalent bonds. In addition, in order to analyze the synthesis mechanism of the composite material, the functional groups of the material were investigated by Fourier transform infrared spectroscopy (FTIR), the morphology and structure were observed by transmission electron microscopy (TEM), and thermodynamic stability was analyzed by thermogravimetry. The flocculation mechanism was studied by testing the zeta potential and GPC spectrum of the organic-inorganic composites. Moreover, the composite material increased the transmittance by 74.33% and decreased the water volume by 84% for simulated oil sand tailings. Ultimately, the degradation experiments showed that the prepared organic-inorganic composite flocculant had nice self-degradation performance, which efficiency could reach over 90% within 2 hours. In conclusion, this material can be employed to enhance the recovery of water from oil sand tailings, also with outstanding degradation characteristics.

Influence of composite flocculant FeCl3–APAM on vacuum drainage of river-dredged sludge

Sludge is an inevitable product of river dredging and is characterized by a high water content, high fluidity, and high heavy metal content. Its treatment requires consideration of the economic and environmental implications. In this study, a composite flocculant comprising anionic polyacrylamide (APAM) and FeCl3 was used in combination with vacuum preloading to conduct indoor tests on the treatment of dredged sludge. The monitored parameters included the water drainage rate and sludge settlement, and the water content and shear strength after testing. The addition of the composite flocculant was found to effectively enhance the flocculation of the soil and increase the soil particle size, resulting in accelerated water drainage, thus improving the treatment effect and the solidification of the contained heavy metals. The treatment was found to be optimized by an APAM:FeCl3 ratio of 1:5 in the composite flocculant, under which the moisture content of the sludge was reduced from 140% to 50%, and the solidification rate of the heavy metals exceeded 88%.

Advanced treatment process for papermaking wastewater by composite photoelectrocatalysis and heterogeneous photocatalysis of nano-TiO2 colloid and its pilot-scale system

It is difficult for papermaking wastewater to reach the discharge standard with only a sequencing batch reactor activated sludge process (SBR). This study developed an advanced wastewater treatment system with nano-TiO2 colloid photoelectrocatalysis and heterogeneous photocatalysis (PEPC). First, the performances of different flocculation processes and their influences on the subsequent PEPC process were studied. The recycling of the nano-TiO2 colloid photocatalyst was further investigated. The results showed that the ternary composite flocculation process using both the inorganic flocculant and the nano-TiO2 colloid (1 × 10-3 wt%) had the best flocculation effect with a suspended solid (SS) removal rate of 93.5% and a chemical oxygen demand (COD) removal rate of 66.9%. It also achieved the best PEPC treatment performance with a COD removal rate of 93.6% in 90 min with the 0.05 wt% dosage of the nano-TiO2 colloid photocatalyst. Moreover, the COD removal rate reached 88.5% after four recyclings of the nano-TiO2 colloid photocatalyst, which demonstrated the excellent reusability of the nano-TiO2 colloid photocatalyst. Finally, based on the PEPC process, an automatic and continuous pilot-scale system was established. Its successful operation suggests the feasibility of operating PEPC technology at an industrial scale.

Drinking water treatment by stepwise flocculation using polysilicate aluminum magnesium and cationic polyacrylamide

In the current work, polysilicate aluminum magnesium (PSAM) and cationic polyacrylamide (cPAM) were stepwise used for drinking water treatment. The flocculant was characterized by fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. PSAM-cPAM was then applied to flocculate the simulated water sample. The simulated water sample was prepared by kaolin and sodium humate. The efficiency of flocculation treatment was highly dependent on the flocculation conditions. Important parameters, such as the pH value of simulated water sample, temperature, settling time, the total dosage of flocculant, and flocculant types, were optimized to ensure an effective flocculation performance. Under optimized conditions, the removal efficiency (more than 98%) was outstanding in terms of turbidity and color removal. In addition, charge neutralization, bridging effect, and co–precipitation interaction could play crucial roles in the flocculation process. Composite flocculants consisting of PSAM and cPAM were found to be environmentally friendly, highly efficient, and fast settling in drinking water treatment.

Optimization of Polyaluminum Chloride-Chitosan Flocculant for Treating Pig Biogas Slurry Using the Box⁻Behnken Response Surface Method.

Flocculation can remove large amounts of nitrogen and phosphorus from wastewater, and the resulting nitrogen- and phosphorus-rich floc can be used to produce organic fertilizer. For biogas slurries containing high levels of nitrogen and phosphorus, ordinary flocculants can no longer meet the flocculation requirements. In this study, to fully utilize the advantages of the two flocculants and achieve efficient removal rates of nitrogen and phosphorus from a biogas slurry, chitosan (CTS) and polyaluminum chloride (PAC) were used as a composite flocculation agent to flocculate pig biogas slurries. The response surface method was used to study the effect of PAC added (PACadded) to the composite flocculant (CF), composite flocculant added (CFadded) to the biogas slurry and the pH on flocculation performance, and optimize these three parameters. In the tests, when the PACadded was 6.79 g·100 mL−1CF, the CFadded was 20.05 mL·L−1 biogas slurry and the pH was 7.50, the flocculation performance was the best, with an absorbance of 0.132 at a wavelength of 420 nm. The total phosphorus (TP) concentration was reduced from 214.10 mg·L−1 to 1.38 mg·L−1 for a removal rate of 99.4%. The total ammonia nitrogen (TAN) concentration was reduced from 1568.25 mg·L−1 to 150.27 mg·L−1 for a removal rate of 90.4%. The results showed that the CF could form larger flocs, and had greater adsorption capacity and more stable flocculation performance than ordinary flocculants. Furthermore, the CF could exhibit better chelation, electrical neutralization and bridge adsorption.

A Molecular-Based Design of RGO/TiO2-PAM Composite Flocculant with Photocatalytic Self-Degrading Characteristics and the Application of the Oil Sand Tailings Flocculant

Polymer flocculation technology has a very broad application in the flocculation industry of oil sand tailings at present. Nevertheless, the most commonly used commercial polyacrylamide flocculant ...

Application of composite flocculants for removing organic matter and mitigating ultrafiltration membrane fouling in surface water treatment: the role of composite ratio

Coagulation prior to the ultrafiltration (UF) process was implemented to improve natural organic matter (NOM) removal and membrane permeability.

Application of Chitosan Composite Flocculant in Tap Water Treatment

The chitosan is a good flocculant for tap water treatment because of its properties such as faster deposition rate and higher removal efficiency for COD (organic matter), SS (suspended solids), and metal ions. However, its high price limits the use in tap water treatment. In this paper, in order to reduce costs, chitosan (CTS), polyaluminum chloride (CF-PAC), and modified rectorite (Al(OH)3 + HCl) were combined to prepare the flocculant for tap water treatment. In order to get the optimal composite flocculant formula, first, we combined these flocculants in two-by-two schema and then we combined all the three flocculants together with various dosing amounts. Through comparison between different combination schemas, the best formula of the composite chitosan flocculant was found to be CTS (ml) : CF-PAC (ml) : modified rectorite (Al(OH)3 + HCl) (ml) = 1 : 30 : 5, with a turbidity removal rate of 96.38% and a removal rate of aluminum up to 80.1%, while the treatment cost is the lowest. In addition, we have designed a cost-effective method for the treatment cost evaluation. As raw water, we used water from the Han River, which is used as raw water at Zonguan Waterworks. In order to show the effectiveness of our optimal composite chitosan formula, we have compared our treatment results to those of the aluminum polyaluminum chloride flocculant currently used in Zonguan’s water treatment plants.

Synthesis and evaluation of a novel inorganic–organic composite flocculant, consisting of chitosan and poly‐ferric cerium silicate

AbstractBACKGROUNDCoagulation/flocculation is widely used in the treatment of dye wastewater because of the low cost, high efficiency, short process and convenient operation. However, with the increase of pollutants in water and in recent years the higher requirement for environment protection, traditional flocculants have found it difficult to meet the processing requirements. Therefore, to develop new, efficient, stable and environment‐friendly flocculants is very necessary and urgent.RESULTSDecoloration performance and mechanism, stability and structure of flocculants were determined from experimental data, and the results indicated that chitosan and poly‐ferric cerium silicate (CTS‐PFCS) flocculant, a three‐dimensional chain‐net structure with bar‐like branches, was a complex compound rather than a simple mixture of raw materials. The decoloration performance and stability of this flocculant was superior to that of poly‐ferric cerium silicate (PFCS) when treating Direct Red dye wastewater, and also it had a wide range of pH application. The main mechanism for flocculation is charge‐neutralization and chemical adsorption in the initial stage of flocculation and later bridge‐aggregation.CONCLUSIONA novel inorganic–organic composite flocculant CTS‐PFCS was successfully synthesized by the combination of chitosan and homemade PFCS. The potential use of chitosan as an organic additive for modifying inorganic polymers flocculant in the clarification of wastewater was demonstrated. © 2018 Society of Chemical Industry

Optimization of flocculation conditions for soluble cadmium removal using the composite flocculant of green anion polyacrylamide and PAC by response surface methodology

In this work, we describe a flocculation performance evaluation of a novel anionic polyacrylamide (APAM) synthesized using low dose γ-ray initiation. The APAM structure and morphology were characterized using Fourier transform-infrared spectroscopy (FTIR), High performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) techniques. In comparison to commercially purchased APAM (Mw = 1.0 × 107), γ-ray initiation was demonstrated to be a more effective method to increase molecular weight, decrease the residual acrylamide monomer, and improve thermal stability. Flocculant performance was evaluated by assessing their ability to remove Cd(II) from water. We utilized the Plackett-Burman (PB), steepest ascent, and response surface methodology (RSM) experimental design to identify the optimal flocculating conditions for the removal of soluble Cd(II). Under optimal conditions [26.84 mg L−1 CaO, 71.28 mg L−1 polyaluminium chloride (PAC) and 2.87 mg L−1 APAM], the maximum percent removal of Cd(II) was observed to reach 93.65%. A potential flocculation mechanism for the Cd(II) removal from water was further studied by evaluating the colloid Zeta potential. Results from these studies demonstrated that PAC had a greater capability to change the Zeta potential of collide under alkaline conditions, while APAM played a critical role in the bridging, enmeshment, and sweeping effect. The composite of two types of predominance makes considerable sense in regards to enhancing flocculating efficiency, decreasing secondary pollution, and reducing flocculant cost.