Inorganic Flocculants Research Articles

Ammonium Metavanadate Fabricated by Selective Precipitation of Impurity Chemicals on Inorganic Flocculants

High purity ammonium metavanadate (NH4VO3) is the most vital chemical to produce V2O5, VO2, VN alloy, VFe alloy and VOSO4, which have some prospective applications for high strength steel, smart window, infrared detector and imaging, large scale energy storage system. NH4VO3 is usually produced by spontaneous crystallization from the aqueous solution due to its sharp dependence of solubility on the temperature. However, hazardous chemicals in industrial effluent, include phosphorate, silicate and arsenate, causing severe damage to the environment. In this work, these impurities are selectively precipitated onto inorganic flocculants, while the vanadate dissolved in an aqueous solution keeps almost undisturbed. Therefore, high purity NH4VO3 is produced by the crystallization from the purified solution. By screening various flocculants and precipitating parameters, polyaluminum sulfate with an optimal amount of 50 g/L, is demonstrated to selectively remove phosphorate, silicate and arsenate, corresponding to the removing efficiency of 93.39%, 97.11% and 88.31%, respectively. NH4VO3 from the purified solution holds a purity of 99.21%, in comparison with 98.33% in the product from the crude solution. This purifying technology cannot only produce NH4VO3 with high added value, but also reduce the environmental pollution of waste liquid.

Performance Analysis of a Profile Control Agent for Waste Drilling Fluid Treatment

A method for the treatment of hazardous waste drilling fluids, potentially leading to environmental pollution, is considered. The waste drilling fluid is treated with an inorganic flocculant, an organic flocculant, and a pH regulator. The profile control agent consists of partially hydrolyzed polyacrylamide, formaldehyde, hexamethylenetetramine, resorcinol, phenol, and the treated waste drilling fluid itself. For a waste drilling fluid concentration of 2500 mg/L, the gelling time of the profile control agent is 25 h, and the gelling strength is 32,000 mPa.s. Compared with the profile control agent prepared by recirculated water under the same conditions, the present profile control agent displays better stability, salt-resistance, and performance.

Printing Ink Wastewater Treatment Using Hydrodynamic Cavitation and Coagulants/Flocculants

Raw printing ink wastewater (PIW) was treated with various inorganic coagulants and organic flocculants (anionic and cationic polyacrylamides). These processes were also examined as post treatment step following hydrodynamic cavitation. Treatment effectiveness was assessed through color, chemical oxygen demand (COD) and total suspended solids (TSS) removal. The addition of 4500 mg L−1 polyaluminum chloride coagulant in undiluted PIW (COD: 17000 mg L−1) resulted in 99% color removal, 96% COD and TSS removal, after settling for 2 h. The addition of 10 mg L−1 of anionic polyacrylamides in the sample reduced settling time to only 5 min, with concomitant 96–98% removal efficiency. The addition of a 4 min hydrodynamic cavitation pretreatment step reduced coagulant addition by 33%, for the treatment of undiluted PIW (with 10 mg L−1 anionic polyacrylamide), while removals were ranged between 96 and 98%. Economic analysis for the undiluted PIW showed that costs were reduced by ca. 20% with the hydrodynamic cavitation pretreatment step. Moreover, sludge characterization showed the presence of maghemite, aluminum chloride and potassium aluminum silicate. Finally, toxicity tests revealed a significant attenuation of the toxic potential of undiluted PIW, thus indicating the enhanced efficiency of the proposed combined process (hydrodynamic cavitation and coagulation/flocculation).

Thermodynamic and kinetic studies on harmful algal blooms harvesting by novel etherified cationic straw flocculant

Harmful algal blooms (HABs) are growing threats that cause tens of billion dollars economic loss annually. Aiming at efficient disposal of HABs, a cheap and eco-friendly cationic straw was developed by etherification of wheat straw, which replaced hydroxyl groups on cellulose by quaternary ammonium groups. It endowed the cationic straw with high positive charge and achieved 93.92% of harvesting efficiency by enhancing HABs cells aggregation via charge neutralization. Different from inorganic salts-based flocculants, HABs harvesting by the cationic straw is a spontaneous and exothermic process with negative ΔG° and ΔH° under all adsorption conditions. Thermodynamics and kinetics analysis elucidated that HABs adsorption process by cationic straw were mainly driven by physical forces. Together, cationic straw preparation and HABs harvesting processes were comprehensively optimized with orthogonal experiments. The work may inspire cost-effective HABs disposal and fill knowledge gaps of process nature for HABs harvesting.

Simultaneous removal of suspended fine soil particles, strontium and cesium from soil washing effluent using inorganic flocculants

The purpose of this study was to remove suspended soil, Sr 2 + , and Cs + that may exist in soil-washing effluents using an inorganic coagulant (J-AF). The major chemical constituents of the flocculant J-AF were SO 3 and CaO, and were confirmed to have thenardite (Na 2 SO 4 ), calcium carbonate (CaCO 3 ), and tychite (Na 6 Mg 2 (CO 3 ) 4 (SO 4 )) crystals. When 10 g/L of J-AF was injected into the turbid solution containing unstably suspended soil particles of < 45 μ m , the suspended soil could be completely precipitated. The agglomerates of suspended soil formed using J-AF had a maximum size of more than 1 mm, due to which sedimentation was effective. The precipitation of suspended soil by J-AF was more favorable under acidic conditions, such as pH 2, 3, and 5. Sr 2 + was mainly removed from the supernatant by adsorption using J-AF, and Cs + was precipitated by J-AF while adsorbed on suspended soil and subsequently eliminated from the supernatant. These results provide that J-AF can be used for the simultaneous removal of suspended soil, Sr 2 + , and Cs + from a radioactive soil suspension. • J-AF successfully flocculated and precipitated suspended soil. • Suspended soil precipitated favorably at pH 2, 3, and 5. • Sr 2+ was adsorbed by soil and J-AF, and was partially co-precipitated. • Cs + precipitated while adsorbed onto the soil and separated from the aqueous phase.

Selection of Microalgae Harvesting Technology for Bio-crude Oil Production

Energy consumption of fossil fuel which keeps increasing has led to the urgency of research and development on the field of renewable energy for the future. Microalgae are considered to be the most promising new source of biomass compared with first and second-generation feedstocks. A great challenge is a choice of an effective approach for microalgae harvesting. Additional challenges of microalgae harvesting come from the small size of microalgae cells (3-30µm) and the similarity of the density of the microalgae cells to the growth medium. This research is aimed to determine the appropriate microalgae harvesting technology for bio-crude oil production. Several potential microalgae harvesting technologies are centrifugation, filtration, inorganic flocculation, organic flocculation, bioflocculation, electrocoagulation, and flocculation-sedimentation. The method used in this research is Analytic Hierarchy Process (AHP). The results indicate that the parameters taken into consideration are energy need (0.339), cost (0.214), risk of contamination (0.098), efficiency (0.133), technology availability (0.066), microalgae strain flexibility (0.079), and production time (0.071). In a case study, the pairwise comparison of seven alternatives each for the harvesting and seven criteria are compared. The best alternative that can be recommended as a microalgae harvesting technology is flocculation-sedimentation with a weight of 0.202.

Thalassiosira pseudonana and Skeletonema costatum biomass optimization: Cultivation, harvesting, extraction of oils and biodiesel and pelletization of the residue

Microalgae are one of the most promising feedstocks for biofuel production that can solve the energy crisis, climate change, and the depletion of fossil fuels. Biorefineries have production capacity bottlenecks that prevent them from being economically profitable, without leaving aside the environmental safety of by-products. This research aims to analyze critical stages such as harvesting or lipid extraction from two microalgae species currently unknown, such as Thalassiosira pseudonana and Skeletonema costatum. Inorganic flocculation with a low concentration of iron or aluminum salts (FeCl3 and Al2(SO4)3) was achieved to recover >60% biomass in just 20 min in both cases. Lipids extractions through chloroform: methanol (solvent ratio 2:1) obtained low performance due to the ionic strength medium. The fatty acid composition of the algae extracts showed that stearic acid (C18:0) and palmitoleic acid (C16:1) were predominant in both species. In addition, residues from the lipid extraction process were used for the manufacture of pellets. The data collected showed that these solid biofuels should be combined with other biomass typologies if the end-use are biomass boilers. The development of these studies provides new information on different microalgae species and their potential to use their biomass through an integrated utilization.

Optimization of Microalgal Harvesting with Inorganic and Organic Flocculants Using Factorial Design of Experiments

Microalgae have a lot of potential as a source of several compounds of interest to various industries. However, developing a sustainable and efficient harvesting process on a large scale is still a major challenge. This is particularly a problem when the production of low-value products is intended. Chemical flocculation, followed by sedimentation, is seen as an alternative method to improve the energetic and economic balance of the harvesting step. In this study, inorganic (aluminum sulfate, ferric sulfate, ferric chloride) and organic (Zetag 8185, chitosan, Tanfloc SG) flocculants were tested to harvest Chlorella vulgaris in batch mode. Preliminary assays were conducted to determine the minimum dosages of each flocculant that generates primary flocs at different pH. Except for chitosan, the organic flocculants required small dosages to initiate floc formation. Additional studies were performed for the flocculants with a better performance in the preliminary assays. Zetag 8185 had the best results, reaching 98.8% and 97.9% efficiencies with dosages of 50 and 100 mg L−1, respectively. Lastly, a 24 full factorial design experiment was performed to determine the effects of the flocculant dosage, settling time, and mixing time on the Zetag 8185 harvesting efficiency. The harvesting efficiency of C. vulgaris was optimal at a dosage of 100 mg L−1 and 3 min of rapid mixing.

Preparation and performance evaluation of hybrid polymer flocculants (PAC‐PAM), and comparison experiments with other flocculants

AbstractUsing the initiator system of potassium persulfate, a new PAC‐PAM organic–inorganic hybrid flocculant was synthesized. This flocculant is used in sewage disposal. When the dosage was 10 mg/L and initial turbidity was 160 NTU, the turbidity removal rate of the heterogeneous flocculant reached the highest point of 95.04%, the water treatment effect of the hybrid flocculant is higher than that of other flocculants. The optimal experimental conditions in this experiment were as follows: the ratio of AM monomer to PAC was 8:2, the mass fraction of the added initiator was 0.2 wt%, the reaction temperature was 50°C, the reaction time was 4 h, and the pH of the effluent was neutral or weakly basic. Under the same dosage and different initial turbidity, the turbidity removal effect of hybrid flocculant is better than compound flocculant and PAM or PAC. The results show that the hybrid flocculant is a new material, which is different from the compound flocculant. Moreover, the hybrid flocculant is almost non‐corrosive to the equipment and has the prospect of industrial application.

Removal of Microcystis aeruginosa cells using the dead cells of a marine filamentous bacterium, Aureispira sp. CCB-QB1.

Inorganic and synthetic flocculants are widely investigated for removing harmful microalgae, such as Microcystis aeruginosa. However, their toxicity and non-biodegradability are shortcomings. Bioflocculants based on extracellular polysaccharides have attracted much attention as alternative flocculants. However, its high production cost is a limiting factor for applying bioflocculants. Here, we investigate the potential of the dead cells of a marine filamentous bacterium, Aureispira sp. CCB-QB1, as a novel flocculant on M. aeruginosa cells. The removal efficiency of M. aeruginosa cells by the dead cells was measured by mixing and shaking both components in a buffer with 5 mM CaCl2 in different incubation times and concentrations of the dead cells. After that, the minimum effective concentration of CaCl2 was determined. The combination effect of FeCl3 and the dead cells on the removal efficiency was tested. The structure of cell aggregates consisted of the dead cells and M. aeruginosa cells were also observed using a scanning electron microscope. The maximum removal efficiency (75.39%) was reached within 3 min in the presence of CaCl2 when 5 mg/ml of the dead cells (wet cells) were added. The optimal concentration of CaCl2 was 5 mM. The combination of the dead cells and a low concentration of FeCl3 (10 mg/L) with 5 mM of CaCl2 significantly improved the removal efficiency by about 1.2 times (P < 0.05). This result indicates that the combination usage of the dead cells can reduce the use of FeCl3. These results indicated that the dead cells could potentially be a novel biolfocculant to remove M. aeruginosa cells.

A comparison study between bioflocculants and PAM for dewatering of ultrafine phyllosilicate clay minerals

Several environmental problems have been reported when synthetic organic and inorganic flocculants are used to treat fluid fine tailings (FFT), especially phyllosilicate clay minerals, generated in the mining plants. These hazardous issues have increased the importance of using natural flocculants from renewable sources (biopolymers). This investigation has explored the impact of proteins (protamine and lysozyme) and polysaccharides (chitosan, pectin, lignin, and alginic acid) as natural flocculants and compared their results in the same conditions by using Polyacrylamide (PAM) as a traditional organic polymer. Ultrafine kaolinite and serpentine particles (−10 μm) were chosen as the challenging gangue minerals for chalcopyrite copper ore (CuFeS2) and pentlandite nickel ore ((Fe, Ni)9S8)), respectively. Capillary suction timer (CST) and filtration tests were considered for comparative assessments. Assessments indicated that PAM in shear rate ~ 20 (1/s) has a viscosity ~90 times higher than the examined biopolymers. This high viscosity limited PAM distribution as a flocculant through the suspensions. Results highlighted that PAM had the highest flocculation activity in low dosages (0.05 and 0.1 wt%) while in dosages above 0.25 wt%, cationic biopolymers; protamine, and lysozyme for kaolinite and anionic pectin for serpentine showed a higher performance than the other polymers. The addition of Ca2+ could increase the dewatering of the clay minerals and promote the flocculation strength of the biopolymers. Generally, results indicated that the flocculation function of protamine and lysozyme (cationic proteins) at the optimum dosage (0.5 wt%) was higher than other tested biopolymers, while pectin (an anionic polysaccharide) improved the dewatering of serpentine particles. Outcomes of this study proved that commercially available bioflocculants have a significant potential to use in the treatment of FFTs and decrease environmental problems that occur by using inorganic and organic flocculants.

Pilot-scale microsand-ballasted flocculation of wastewater: turbidity removal, parameters optimization, and mechanism analysis.

The flocs formed during microsand-ballasted flocculation (MBF) have attracted much attention. However, few studies have reported on comprehensive process parameters of MBF and its mechanism is still not well understood. Jar test and pilot-scale continuous experiments were here conducted on two kinds of simulated wastewater, labeled S1 (21.6-25.9 NTU) and S2 (96-105 NTU). Results revealed the hydraulic retention time ratio in the coagulation cell, injection and maturation cell, lamella settler of pilot-scale MBF equipment was 1:3:7.3. The optimum poly aluminum chloride doses for samples S1 and S2 were 0.875 g/L and 1.0 g/L. Besides, the optimum size of microsand was 49-106 μm and the optimum dose was 1.0 g/L. Under aforementioned conditions, the effluent turbidity of S1 was below 0.47 NTU, even lower than the Chinese drinking water standard; that of S2 was below 1.7 NTU, meeting the Chinese recycled water standard. Turbidity removal ranged from 98.0 to 98.8% for S1 and 98.5 to 99.5% for S2 when microsand was added. Therefore, microsand addition enhances MBF performance, where microsand serves as an initial core particle. Some microsand core particles bond together to form a dense core structure of micro-flocs by the adsorption bridging of inorganic polymeric flocculant. Moreover, the size of the largest micro-flocs may be controllable as long as the effective energy dissipation coefficient is adjusted appropriately through specific stirring speeds. This work provides comprehensive pilot-scale process parameters for using MBF to effectively treat wastewater and offers a clearer explanation of the formation mechanism of microsand-ballasted flocs.

Study on the Effect of Flocculation and Sedimentation on the Mechanical Properties of Iron Tailing Sand

Tailings sand is the dam‐building material of the tailings dam accumulation sub‐dam, and its mechanical properties directly affect the safety and stability of the whole tailings dam. With the improvement of mineral sorting technology, the content of fine and ultrafine particles in the tailings gradually increases, which will affect the mechanical strength of tailings accumulation sub‐dam. To improve the settling effect of tailings accumulation in the Chengchao iron ore mine (China), the effect of iron tailings flocculation and settling law on the mechanical properties of tailings sand was studied. Polymerized iron sulfate (PFS) as an inorganic polymer flocculant, compared with the traditional flocculant, has a stronger flocculation and adsorption capacity, is widely used in drinking water, industrial wastewater, and domestic sewage treatment, is an anionic polyacrylamide (APAM‐800) for polymer compounds, mainly divided into nonionic, cationic, and anionic three, and is commonly used mine flocculant at home and abroad. Through different flocculants, PFS, and APAM‐800 compound flocculation and settling experiments, the effect of the flocculant‐dosing scheme on the settling rate and turbidity of clarified liquid was determined, and the change in tailings consolidation shear strength of the best dosing scheme was measured. The experimental results showed that the settling rate of iron tailings was the fastest when PFS was used in combination with APAM‐800 at 1.2 g L−1 and 0.20 g·L−1 dosages, respectively. The direct shear test results showed that the internal friction angle of tailings sand increased by 2.18°, the cohesion increased by 5.814 kPa, and the shear resistance of flocculated settled tailings increased, which can effectively improve the safety factor of tailings sand pile sub‐dam.

The Study of Optimization of Flocculation and Destabilization Technology of Waste PEM Drilling Fluid in Bohai Oilfield

In light of the difficulty of solid-liquid separation of waste PEM drilling fluid in the Bohai oilfield, constructing an inorganic-organic flocculation system is proposed and the processing method of destabilization technology is optimized. The biggest influence factor on the flocculation process of PEM drilling fluid was determined by designing an orthogonal test. The flocculation mechanism was researched through single factor optimization, combined with zeta potential and particle size distribution test. The results showed that the most significant factors affecting the flocculation of waste PEM drilling fluid were the dosage of inorganic flocculant CaCl2 and flocculation pH value. When the dosage of inorganic flocculant CaCl2 was 1.2% (w/v), the dosage of organic flocculant SDYJ-2 was 0.05%, the flocculation pH value was 3, and the flocculation time was 5 min, the flocculation technology reached the optimization and then the liquid yield can reach 70.96%. The mechanism of flocculation and destabilization was as follows: the inorganic flocculant of CaCl2 mainly reduced the zeta potential of clay particles through electric neutralization. 1% CaCl2 could reduce the potential mean value of drilling fluid system from -38.1 mV to -32.5 mV, and then decrease the repulsion among suspensions. Through bridging curling and electric neutralization, the organic flocculant of SDYJ-2 can absorb and wrap the clay particles after flocculation destabilization to form a network spatial structure, which made clay particles aggregate into large flocs and particles. D50 can increase by 21.5 times, when the concentration of SDYJ-2 was 0.15%.

Construction and Application of Flocculation and Destability System of Biodrill-A Drilling Fluid in Bohai Oilfield

To protect the marine ecological environment of Bohai Bay, the waste drilling fluid in Bohai oilfield have to be treated. In the light of the composition characteristics of Biodrill-A drilling fluid, the compounding method of the inorganic–organic flocculants was adopted to assist the flocculation and solid–fluid separation of Biodrill-A drilling fluid. Through the orthogonal test design, the main factors impacting the flocculation effect on Biodrill-A drilling fluid were found to the concentration of inorganic flocculant CaCl2 and the flocculation pH value. The optimal flocculation treatment was further obtained through single-factor optimization. Specifically, when the inorganic flocculant CaCl2 concentration was 0.9 w/v%, the organic flocculant concentration was 0.01 w/v%, the flocculation pH was 8, and the flocculation time was 7 min. Eventually, the final dewatering rate could reach 84.02%. In the optimized compound flocculants, the inorganic flocculant CaCl2 reduced the zeta potential of clay particles by electric neutralization to decrease the repulsion among particles, and the organic one could absorb and wrap the clay particles through bridging curling and electric neutralization after flocculation destabilization. Both inorganic and organic flocculants facilitated the large flocs and particles of clay particles. The field test showed that the inorganic–organic flocculants were suitable for the on-line flocculation treatment process based on centrifugal machine. The waste drilling fluid was reduced by 82%, and the water content of the separated solid phase was as low as 25.7%.

Enhanced coagulation for TiO2-NPs removal by using a hybrid flocculant

A hybrid flocculant, PAC-CA, with the advantages of inorganic and organic flocculants, was prepared, and the coagulation behavior and floc characteristics of PAC-CA for removing titanium dioxide nanoparticles (TiO2-NPs) under different conditions were studied. The effects of monomer mass ratio, initiator concentration, hydroxyl aluminum ratio, reaction temperature, and polymerization time on the coagulation performance for TiO2-NP removal were studied. PAC-CA was characterized through SEM, FT-IR, TG-DSC, XRD, XPS, and Ferron complex colorimetric characterization. The characterization results showed that PAC-CA was successfully copolymerized using AlCl3, carboxymethyl chitosan, and acrylamide. The high content of Alb in PAC-CA helped improve the coagulation performance. When the dosage was 30 mg/L, the pH was 8, the stirring intensity was 200 s−1, and the settling time was 30 min, the optimal removal rates for TiO2-NPs and turbidity were 87.30% and 91.72%, respectively. Kaolin could effectively improve the TiO2-NP removal efficiency and promote the density and particle size of flocs. Humic acid exerted an inhibitory effect on coagulation efficiency with loose and small flocs.

Aspergillus oryzae, a novel eco-friendly fungal bioflocculant for turbid drinking water treatment

• An eco-friendly fungal bioflocculant was developed for turbid water purification. • More than 85% turbidity can be removed in a wide pH value (4.0–9.0). • Adsorption and charge attraction played dominant role in flocculation process. • The functional groups on fungal pellets contributed to turbidity flocculation. • Fungal pellet can be directly used as bioflocculant rather than fungal metabolites. The residuals of aluminum (Al), iron (Fe), and acrylamide are always present when traditional inorganic coagulants and organic polyacrylamide flocculants are used, causing environmental security problems. Nevertheless, most microbial flocculants are nontoxic, cause no secondary pollution, and easily biodegrade, and thus efficient and eco-friendly bioflocculants are valuable. Herein, Aspergillus oryzae , a food fermentation fungus, was cultured and developed as a bioflocculant for turbid drinking water treatment. The physical and chemical structures of A. oryzae was characterized, and flocculation performance was evaluated in turbid drinking water treatment. Flocculation efficiency of 91.09% was obtained in the fungal pellets at a culture time of 72 h, flocculant dosage of 3.2 g/L, and pH of 5.0. More than 85% flocculation efficiency was achieved in a wide pH range from 4.0 to 9.0. The removal mechanism was investigated through zeta potential, field emission scanning electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. Results showed that functional groups, such as hydroxyl, amide, and carboxyl, in the metabolites secreted by the fungal pellets contributed to the flocculation process through adsorption. Zeta potential analysis indicated that electrostatic force contributed a positive effect. Fungal hyphae can be directly used as bioflocculants rather than fungal metabolites. This feature is favorable and convenient to drinking water treatment.

Efficient separation performance of suspended soil and strontium from aqueous solution using magnetic flocculant

This study aimed at magnetically separating suspended soil and Sr2+ from a soil suspension using a magnetic flocculant (MNP/IF). MNP/IF was prepared using the electrostatic interaction between the magnetite particles and the inorganic flocculant (IF) based on CaCO3 and Na2SO4. By analyzing the physical properties of MNP/IF, it was confirmed that MNP/IF was successfully imparted with magnetism and had excellent adsorption capacity for Sr2+. The optimal MNP/IF dosage for the sedimentation of suspended soil was determined to be 0.3 g/g (mass ratio of flocculant to soil). Compared with raw IF, MNP/IF showed better flocculation performance to suspended soil for a shorter sedimentation time. The lower the pH, the more favorable the flocculation-sedimentation process of the suspended soil by MNP/IF, since Ca2+ and Mg2+, which are the most common strong flocculators, were further eluted from IF under acidic conditions. MNP/IF also showed excellent removal performance for Sr2+, exhibiting maximum Sr2+ adsorption capacities of 163.6 mg/g in the flocculation-sedimentation reaction of suspended soil. The Sr2+ adsorption process was consistent with the Langmuir model and followed the pseudo-second-order kinetics. These results provide that MNP/IF can be used for the simultaneous removal of suspended soil particles and Sr2+ from a radioactive soil suspension.

Preparation of fly ash-based flocculant and flocculation performance

Using fly ash from a thermal power plant in Yingkou City as raw material, The inorganic polymer flocculant polyaluminum ferric chloride (PAFC) was prepared by sodium carbonate impregnation, high temperature roasting activation, and acid leaching. The influence of activation temperature and activation time on the leaching of aluminum and iron was investigated through single factor test and orthogonal test. The PAFC preparation conditions were optimized, and the prepared PAFC flocculant product was applied to kaolin turbidity water. The test results showed that the content of aluminum in fly ash was 7.08%, and the content of iron was 4.95%. The mass ratio of the activator sodium carbonate and fly ash was 10:7, the activation temperature was 800°C, and the activation time was 2h. The leaching rates of aluminum and iron were the highest, 88.31% and 53.66% respectively. The optimal conditions for the preparation of the flocculant were as follows: the molar ratio of aluminum to iron was 5.7:1, and the reaction time was 1.5h. The liquid product obtained under these conditions was yellowish brown, and the solid product obtained after being dried was yellow powder.

Synthesis of a new polyunsaturated cationic crosslinker by a new micro‐polycondensation reaction as a critical modifier of polycationic flocculant for purifying dyeing wastewater

AbstractBACKGROUNDThis work explored a complete evolutionary process, from discovering a new reaction and synthesizing a new crosslinker intermediate, to product application in the purification of dyeing wastewater.RESULTSA new micro‐polycondensation reaction between propylacryloyloxypropyldimethylamine and epichlorohydrin was first observed, forming a new polyunsaturated cationic crosslinker (poly (2‐hydroxypropylacryloyloxypropyldimethylammonium chloride) (PHPAC), abbreviating HPAC unit as the repeating unit); meanwhile, this new PHPAC crosslinker was just a critical modifier of a polycationic flocculant. When the thimbleful of PHPAC crosslinkers containing only 0.2% molar percentage of HPAC units were incorporated into a polycationic skeleton of poly (acryloyloxyethyltrimethylammonium chloride) (PDAC), the application properties of the obtained modified product (known as SC‐PDAC) were greatly improved compared to the unmodified product of PDAC. The cost for preparing the modified product of SC‐PDAC was hardly increased because the quantity of HPAC modifier used was minimal. The multi‐dimension flocculation interactions of SC‐PDAC with the anionic dyes allowed the SC‐PDAC to realize a more efficient purification of dyeing wastewater than the unmodified PDAC. The obtained SC‐PDAC could remove 99.10% of the dyes Reactive Scarlet 3BS and 96.69% of the dyes Methyl Blue when used for purifying the dyeing wastewater. In real engineering applications, the further complex interactions of SC‐PDAC with certain inorganic flocculants and coagulant aids would allow the flocs to be quickly formed, condensed, and aggregated, so as to realize a fast purification of dyeing wastewater within 10 s. The successful implementation of a simulation amplification experiment for treating a 4.0 L dye solution further confirmed that the SC‐PDAC had good potential to be applied in real water treatment engineering.CONCLUSIONSTherefore, as expected, it could be regarded as an economic and facile modification way to obtain the efficient organic cationic flocculant by selecting the PHPAC crosslinker as a critical modifier. © 2021 Society of Chemical Industry (SCI).