Polyaluminum Ferric Chloride Research Articles

Simultaneous enhanced phosphorus removal and hydration reaction: Utilisation of polyaluminium chloride and polyaluminium ferric chloride to modify phosphogypsum-based excess-sulphate slag cement

This study employed polyaluminium chloride (PAC) and polyaluminium ferric chloride (PAFC) for the phosphorus removal released during the hydration of phosphogypsum-based excess-sulphate slag cement (PESSC), as well as microstructure modification. The results indicated that the PESSC samples presented shorter setting times and bleeding rates with further modifier addition due to the effective phosphorus removal and rapid establishment of the flocculated structure. Compressive and flexural strengths were also significantly enhanced in modified samples at each age, where they exceeded 58 MPa and 13 MPa at 180 d, respectively, when PAC and PAFC supplements were within 1.0%. Furthermore, the distinctions in the effect mechanism of two functional compositions (Keggin-Al13 and iron phase) in modifiers have also been studied. In contrast to affecting the microstructure of C-(A)-S-H gel, the released Al(OH)4‐ and Fe(OH)4‐ during hydrolysis often acted with sulphate and portlandite, leading to a higher level of ettringite formation, as well as hydration degree. Comparatively, the introduction of the iron phase adversely impacted pH value development of pore solution and retarded the activation process of slag at early age, while also promoting continuous hydration at later age. The optimisation in the microstructure of PESSC also contributed to impurities solidification, presenting the lower leaching concentration in an acid environment. Overall observations suggested that adding 0.5%–1.0% PAC or PAFC in the PESSC are capable of enhancing not only its engineering properties but also promoting its sustainability.

Enhanced removal of polystyrene microplastics through coagulation using polyaluminum ferric chloride with Opuntia Milpa Alta particles

Microplastics in surface water and groundwater are posing significant risks to both ecological systems and human health. Conventional coagulants are limited in their efficacy for microplastic removal and may potentially lead to secondary pollution. The present study investigated the effectiveness of Opuntia Milpa Alta (OMA) particles, as a natural coagulant, in combination with polyaluminum ferric chloride (PAFC) to remove polystyrene (PS) microplastics. The results demonstrated the pivotal role of OMA in facilitating the coagulation. Specifically, the combination of 15 mg/L of OMA and 30 mg/L of PAFC achieved a removal rate of 94.8 %. Zeta potential analysis, scanning electron microscopy (SEM) characterization, and Fourier transform infrared spectroscope (FTIR) analysis revealed that the promotion mechanisms by OMA primarily involved charge neutralization and adsorption bridging, attributed to the presence of polygalacturonic acid from OMA's mucilage, the rough surface and the mesh structures of OMA. Influences of Cl−, SO42− and HCO3− within the concentration range found in surface and groundwater were also studied. Furthermore, a cost assessment demonstrated that the incorporation of OMA not only enhanced the coagulation performance but also reduced overall costs. These findings will provide valuable insights towards the development of cost-effective techniques for the removal of microplastics from water.

Enhanced dewatering of dredging slurry by Fenton preoxidation and composite coagulants: optimization experiments and dewatering mechanisms.

In this work, the Fenton preoxidation and composite coagulant method was used to carry out the rapid dewatering experiment of Chaohu Lake (China) dredging slurry. The changes in extracellular polymeric substances (EPS), particle size distribution, zeta potential, specific resistance to filtration (SRF), and capillary suction time (CST) of the dredging slurry were characterized. The results showed that the molar ratio of H2O2 and Fe2+ had the greatest effect on the dewatering of dredging slurry by Fenton preoxidation. The coagulant selected through the coagulation test was polyaluminum ferric chloride. The model simulated by the response surface method exhibited significant adaptability and high accuracy (p < 0.01, R2 = 0.9461, accuracy is 12.115). Fenton preoxidation resulted in the transformation of tightly bound EPS to soluble EPS. After preoxidation-coagulation treatment, the dewatering performance of the slurry improved significantly. The EPS quantity rose by 20.3%, while the SRF (3.65 × 109 s2/g), CST (71.25s), and zeta potential (- 28.0mV) shifted to 0.33 × 109 s2/g, 27.60s, and - 14.9mV, respectively. The disintegration of EPS by Fenton peroxidation and the subsequent adsorption bridging and charge neutralization through coagulation were the key mechanism for improving the dewatering performance of the dredging slurry.

Synergistic coagulation of hybrid polyaluminum ferric chloride coagulant for water treatment

Synergistic coagulation of hybrid polyaluminum ferric chloride coagulant for water treatment

Efficient, quick, and low-carbon removal mechanism of microplastics based on integrated gel coagulation-spontaneous flotation process

To address the problems of unstable efficiency, long treatment period, and high energy consumption during microplastics (MPs) removal by traditional coagulation–flotation technology, a gel coagulation–spontaneous flotation (GCSF) process is proposed that employs laminarin (LA) as the crosslinker and polyaluminum chloride (PAC)/polyaluminum ferric chloride (PAFC) as the coagulant to remove MPs. Herein, the effects of GCSF chemical conditions on microplastic-humic acid composite pollutants (MP-HAs) removal were investigated, and the removal mechanisms were analyzed through theoretical calculations and floc structure characterization. Results showed that an LA to PAC/PAFC ratio of 2.5:1 achieved the highest removal of HA (86 %) and MPs (93 %–99 %) in short coagulation (< 1 min) and spontaneous flotation (< 9 min) period. PAC-LA exhibited strong removal ability for MP-HAs while PAFC-LA induced fast flotation speed. The peak intensity and peak shift in Fourier-transformed infrared and X-ray photo-electron spectra indicated that the removal mechanisms of MPs include hydrogen bond adsorption and the sweeping effect, mainly relying on –OH/–C = O on the MPs surface and entrapment of gel flocs with a high degree of aggregation, respectively. The extended Derjaguin-Landau-Verwey-Overbeek calculation also revealed that interactions between PAC/PAFC-LA and MP-HAs were mainly polar interaction (hydrogen bonding) and intermolecular attraction interaction (Lifshitz-van der Waals force), and the sweep effect was reflected by intermolecular interaction. In addition, density function theory calculations indicated that –OH in LA mainly adsorbs DO through a double hydrogen bond configuration, and the crosslinking ligand FeO6/AlO6 assists in DO absorption by –OH.

Recycling of sludge residue as a coagulant for phosphorus removal from aqueous solutions.

Phosphorus pollution poses a significant challenge in addressing water contamination. The coagulant is one of the effective methods to remove phosphorus from wastewater. Abundant Al and Fe oxides in sludge residue make it have great potential to synthesize water treatment coagulants. However, the utilization of sludge residue for preparation of coagulant was seldom investigated. In this study, we fabricated a novel coagulant, polyaluminum ferric chloride (SM-PAC), using sludge residue as a raw material through acid leaching and polymerization processes. Characterization results confirm that the parameters of SM-PAC meet the specifications outlined in the national standard (GB/T 22627-2022). We investigated the effects of pH, dosage, initial phosphorus concentration, and contact time on the removal efficiency of SM-PAC. As anticipated, the prepared SM-PAC exhibited a significant efficacy in removing phosphorus, meeting the discharge standards set for municipal sewage. Furthermore, the adsorption kinetics analysis suggests that the predominant mode of phosphorus adsorption on SM-PAC is chemical adsorption. Furthermore, the SM-PAC was employed in the actual wastewater treatment plant and exhibited excellent efficiency in phosphorus removal. The utilization of SM-PAC can not only effectively address the issue of sludge disposal but also achieve the goal of "treating waste with waste." It is expected that the proposed method of reusing sludge residue as a resource can provide a sustainable way to synthesize a coagulant for phosphorus removal.

Inorganic flocculant-based soybean urease extraction and its effect on biomineralization

Enzyme induced carbonate precipitation (EICP) based on self-extracted crude soybean urease solution (CSUS) is a promising method for soil improvement. However, the deionized water-extracted CSUS usually contains a large amount of impurities that easily lead to bioclogging during the biogrouting process, resulting in a nonuniform biomineralization effect. In this study, a purification method using inorganic flocculants is proposed to extract CSUS with relatively high purity and urease activity (UA) for EICP method. Seven commonly used inorganic flocculants were adopted in this study, including KAl(SO4)2•12H2O, AlCl3•6H2O, Al2(SO4)3•18H2O, Fe2(SO4)3, poly aluminum chloride, poly ferric sulfate, and poly aluminum ferric chloride. Three sets of tests, including CSUS extraction tests, solution tests, and sand column treatment tests, were conducted to investigate the feasibility and validity of this purification method. The test results show that inorganic flocculants could effectively reduce the turbidity of the extracted CSUS, avoid the bioclogging during biogrouting, and thus improve the biomineralization effect of the CSUS-based EICP method. Compared with deionized water-based CSUS, at least 60% of the impurities in CSUS can be removed at optimal flocculant contents when the soybean powder content is 100 g/L. On the other hand, the flocculants would also cause a reduction in the UA of the extracted CSUS. Considering the UA, turbidity, and biomineralization effect of the extracted CSUS, the optimal inorganic flocculants and their contents are recommended to be 3.0 g/L for KAl(SO4)2•12H2O, 2.0 g/L for AlCl3•6H2O, 2.5 g/L for Al2(SO4)3•18H2O under the tested conditions, respectively.

Electron beam radiation coupled to flocculation for advanced treatment of coking and dyeing wastewater: Performance and synergistic effect

Advanced treatment of industrial wastewater is a tough problem in the field of wastewater treatment. In this study, the electron beam radiation coupled to flocculation process was firstly developed and investigated for the advanced treatment of coking and dyeing wastewater. Three different coupled processes were studied, i.e. electron beam radiation followed by flocculation process (EBF), flocculation followed by electron beam radiation process (FEB), and simultaneous electron beam radiation and flocculation process (SEBF). It was found that different processes had various performances in the removal of targeted organic pollutants. For humic acid, FEB with poly aluminum ferric chloride (PAFC) as flocculants showed the best synergistic effect at 10 kGy, in which the removal of humic acid was 95.2%, while SEBF exhibited the inhibition effect under all the conditions. For Rhodamine B, EBF with PAFC had the highest synergistic effect at 10 kGy, in which the removal of Rhodamine B was 87.4%. For phenol, SEBF with PAFC as flocculants showed the highest synergistic effect at 10 kGy, in which the phenol removal was 64.2%. The transformation of organic pollutants, such as the polymerization was the main reason for the synergistic effect of EBF, while the dissolved iron ions and the enhanced oxidation made major contribution to the synergistic effect of FEB, and the structural change of flocculants and the transformation of organic pollutants during the process of electron beam radiation was mainly responsible for the synergistic effect of SEBF. EBF showed better performance in COD removal for actual coking and dyeing wastewater than FEB, indicating that electron beam radiation could promote the flocculation effect. Considering the operation procedure and treatment cost comprehensively, EBF with PAFC is recommended for the advanced treatment of actual coking and dyeing wastewater. This study could provide a novel and effective method for the advanced treatment of industrial wastewater.

The application of chitosan quaternary ammonium salt to replace polymeric aluminum ferric chloride for sewage sludge dewatering

Inorganic coagulants such as poly aluminum ferric chloride (Al/Fe) are applied conventionally to sewage sludge dewatering and can be retained in the sludge cake, causing its conductivity to increase and generate secondary pollution. To reduce these disadvantages, there is a need to develop alternative, more sustainable chemicals as substitutes for conventional inorganic coagulants. In the present investigation, the application of a polymeric chitosan quaternary ammonium salt (CQAS) is explored as a complete, or partial, replacement for Al/Fe in the context of sludge dewatering processes. Laboratory experiments using digested sewage sludge showed that CQAS could effectively substitute for over 80 % of the Al/Fe inorganic coagulant in the sludge dewatering process. This substitution resulted in a reduction of sludge cake conductivity by more than 50 %. Simulation of sludge dewatering curves and imaging of the sludge surface indicated that the addition of CQAS led to an increase in nanosized pores, and a decrease in the specific resistance of the sludge filter cake as the dosage of Al/Fe decreased to around 30 %. The variations of fluorescence emission, quantum yield and carboxylic and amino groups, suggested that the chelating of Al/Fe decreased due to the bridging effects of CQAS. The CQAS had different flocculation bridging effects on various EPS fractions, which varied the amount of protein chelated with Al/Fe in each fraction. This study provides new information about the benefits of replacing conventional inorganic coagulants with natural organic polymers for sewage sludge dewatering, in terms of reduced sludge cake conductivity and greater dry solids content.

Enhanced Removal of Polystyrene Microplastics from Water Through Coagulation Using Polyaluminum Ferric Chloride with Coagulant Aids

Enhanced Removal of Polystyrene Microplastics from Water Through Coagulation Using Polyaluminum Ferric Chloride with Coagulant Aids

Effective treatment of leachate concentrate from waste incineration plant by combination of coagulation and direct contact evaporation

In order to verify that coagulation as pre-treatment can reduce the temperature of the hot air used for direct contact evaporating the leachate concentrate (LC) and low-grade waste heat such as exhaust steam in the waste incineration plant can be used to evaporate the LC. The supernatants after coagulation using polymerized ferrous sulfate (PFS), polymeric-aluminum (PAC), polymeric silicate aluminum ferric (PSAF) and poly-aluminum ferric chloride (PAFC) as coagulants were further treated in a lab-scale direct contact evaporation system. The results showed that the best performance with removal efficiencies of COD and NH3–N of 58.70% and 29.09% was achieved after coagulation when PAFC dosage = 15 g/L, PAM dosage = 30 mg/L and initial pH of supernatant = 6. After coagulation, a large amount of the fulvic-like acid and aromatic heterocyclic compounds were removed and the degree of complexity and aromaticity of organics decreased. After direct contact evaporation, using PAFC as coagulant still was the best selection due to its lowest concentrations of COD and NH3–N (22 mg/L and 1.02 mg/L) in the condensate produced by this two-stage treatment when initial pH of supernatant was 6 during evaporation and the condensate produced by this two-stage treatment met the water quality standard for using as supplying water for circulating cooling water system when temperature of hot air used for heating LC was at low temperature (250 °C). The fulvic-like acid and aromatic heterocyclic compounds in the condensate continuously reduced. Phenol, adamantane, 1-isocyanato, phthalic anhydrid, tri(2-chloroethyl) phosphat, Heptadecane, 2-methyl, ginsenol and Octadecane, 2-methyl- in the condensate obviously decreased. The effect of four coagulants as pretreatment on reducing the temperature of hot air used for evaporating LC was ranked as PAFC > PFS > PAC > PSAF. PSAF was not recommended due to the large amount of NH3–N produced when using PSAF to treat the LC.

Fluoride removal from coal mining water using novel polymeric aluminum modified activated carbon prepared through mechanochemical process

Defluoridation of coal mining water is of great significance for sustainable development of coal industry in western China. A novel one-step mechanochemical method was developed to prepare polymeric aluminum modified powder activated carbon (PAC) for effective fluoride removal from coal mining water. Aluminum was stably loaded on the PAC through facile solid-phase reaction between polymeric aluminum (polyaluminum chloride (PACl) or polyaluminum ferric chloride (PAFC)) and PAC (1:15 W/W). Fluoride adsorption on PACl and PAFC modified PAC (C-PACl and C-PAFC) all reached equilibrium within 5 min, at rate of 2.56 g mg-1 sec-1 and 1.31 g mg-1 sec-1 respectively. Larger increase of binding energy of Al on C-PACl (AlF bond: 76.64 eV and AlFOH bond: 77.70 eV) relative to that of Al on C-PAFC (AlF bond: 76.52 eV) explained higher fluoride uptake capacity of C-PACl. Less chloride was released from C-PACl than that from C-PAFC due to its higher proportion of covalent chlorine and lower proportion of ionic chlorine. The elements mapping and atomic composition proved the stability of Al loaded on the PAC as well as the enrichment of fluoride on both C-PACl and C-PAFC. The Bader charge, formation energy and bond length obtained from DFT computational results explained the fluoride adsorption mechanism further. The carbon emission was 7.73 kg CO2-eq/kg adsorbent prepared through mechanochemical process, which was as low as 1:82.3 to 1:8.07 × 104 compared with the ones prepared by conventional hydrothermal methods.

Using N-TiO2 to enhance the coagulation of Oscillatoria sp. and subsequently degrade cells and their metabolites in sludge under visible light

Oscillatoria, a common genus of filamentous cyanobacteria, has unsatisfactory removal efficiency in drinking water treatment plants, and the cyanobacteria will accumulate and release cyanotoxins into the sludge. This study therefore used photocatalyst particles (nitrogen-doped TiO2 (N-TiO2)) as ballast to enhance the coagulation of Oscillatoria sp. and to degrade both the cells and the metabolites in sludge by visible-light photocatalysis. Results show that combining 100 mg/L N-TiO2 with different coagulants (polyaluminium ferric chloride (PAFC), FeCl3, or AlCl3) was able to improve the Oscillatoria sp. removal efficiency of coagulation to 95 %, and there were no floating flocs. The addition of N-TiO2 resulted in less-negative electrokinetic potentials of Oscillatoria sp. aggregates, enhanced the adsorption bridging effect, and increased the density and compactness of flocs. N-TiO2 had little effect on the integrity of Oscillatoria sp. cells and did not cause the release of cylindrospermopsin (CYN) during coagulation. In the photocatalysis of Oscillatoria-laden sludge 100 mg/L N-TiO2 effectively inactivated Oscillatoria sp. cells within 48 h, regardless of the type of coagulant. After photocatalytic treatment the cell wall was rough and deformed and most of the cell cytoplasm had been removed. Furthermore, the content of extracellular organic matter in sludge supernatant was significantly reduced. After the 48-h treatment 89.2 % of total CYN in the sludge was able to be degraded. This study therefore suggests that N-TiO2 enhances coagulation technology can not only improve the efficiency of removal of filamentous cyanobacteria, but also reduce the ecological risk of sludge discharge and facilitate the reuse of sludge supernatant.

Effective and mechanistic insights into reverse osmosis concentrate of landfill leachate treatment using coagulation-catalytic ozonation-bioaugmentation-based AnMBR

Landfill leachate membrane concentrates containing high concentrations of organics pose a major threat to the environment, and efficient treatment methods are urgent issue. In this study, a coagulation-catalytic ozonation-bioaugmentation-based anaerobic membrane bioreactor (CCOB-AnMBR) process was applied to treat reverse osmosis concentrate (ROC) of landfill leachate. Compared with polyaluminum ferric chloride (PAFC) and prefrontal cortex (PFC), coagulation using polyferric sulfate (PFS) effectively removed refractory contaminants including macro molecular organics (MMOs), benzene ring compounds (BRCs), humic acid (HA), and fulvic acid (FvA) in ROC of landfill leachate, with average 78.3%, 53.5%, 34.7% and 34.3%, respectively. Catalytic ozonation with MnOx-CeOx-Al2O3 increased the biodegradability index by degrading refractory organic compounds, which facilitated subsequent biological treatment of ROC. The oxidation of mostly occurs at the solid–liquid interface and the presence of MnOx-CeOx-Al2O3 nanocatalyst enhanced ozone decay and increased generation of hydroxyl radical (•OH) and singlet oxygen (1O2) in ROC. In addition, bioaugmentation using recombinant genetically engineered Desulfovibrio vulgaris expressing Sat and dsrAB (rGEDEV-sds) promoted metabolism of sulfate by driving transfer sulfate from the environment into the cell and sulfate dissimilation reduction process. Bioaugmentation-based AnMBR (Bio-AnMBR) caused complete degradation of the total organic carbon (TOC), enhanced degradation of leachate pollutions, and decreased the concentration of sulfate in ROC. The macro molecular organics, refractory organic contaminants, the residual coagulation-resistant substances (CRS), and heavy metal were effectively degraded in the Bio-AnMBR system. Furthermore, CCOB-AnMBR exhibits high processing efficiency in the degradation of the contaminants in ROC of landfill leachate. Overall, this excellent performance proves the feasibility and elucidates the mechanism of CCOB-AnMBR process for the removal of contaminants in ROC of landfill leachate.

Mainstream wastewater treatment by polyaluminium ferric chloride (PAFC) flocculation and nitritation-denitritation membrane aerated biofilm reactor (MABR)

To reduce the carbon emission of sewage treatment, a novel adsorption-biodegradation (A-B) process, flocculation pretreatment as A-stage and nitritation-denitritation MABR as B-stage, was proposed in the study. It was found that 27.37 %–49.69 % of organics can be removed from actual wastewater by flocculation with polyaluminium ferric chloride (PAFC). The pretreated wastewater could be further treated by nitritation-denitritation MABR with low aeration pressure (2–5 kPa) without any extra organics. The NH4+-N, total nitrogen (TN), and chemical oxygen demand (COD) removal efficiency can reach 100 %, 84.04 %, and 98.54 %, respectively. It was also found that the relative abundances of ammonia-oxidizing bacteria (AOB) (3.81 %–4.76 %) and denitrifying bacteria (DB) (4.30 %–5.59 %) were higher than that of nitrite-oxidizing bacteria (NOB) (2.08 %–2.39 %) in the MABR even after 130 days of operation according to the microorganism identification by 16S rRNA sequencing technology. This implied that low oxygen aeration in MABR can prevent NOB from becoming dominant bacteria. Furthermore, it was found that there were indeed traces of anaerobic ammonia oxidation (Anammox) bacteria (0.04 %–0.08 %) and were closely surrounded by other microorganisms in the MABR based on fluorescence in situ hybridization (FISH) technology. In addition, the microbial nitrogen metabolism process in the MABR was further analyzed according to the Kyoto Encyclopedia of Genes and Genomes (KEGG). The promising mainstream A-B process proposed in this study was expected to achieve nitrogen removal with little carbon and energy consumption in wastewater treatment plants (WWTPs).

Optimization of a compact on-site stormwater runoff treatment system: Process performance and reactor design

Stormwater runoff has become a major anthropogenic urban pollution source that threatens water quality. In this study, coagulation-sedimentation, and ammonium ion exchange and regeneration (AIR) modules were coupled as a CAIR system to efficiently treat stormwater runoff. In the coagulation module, 99.3%, 91.7%, and 97.0% of turbidity, total phosphorus, and chemical oxygen demand could be removed at an optimized poly-aluminum ferric chloride dosage of 30 mg/L, and the continuous experiment confirmed that the full load mode was more suitable for its rapid start-up. In the AIR module, dynamic ammonium removal indicated that the breakthrough time decreased with the rising initial concentration and superficial velocity. The Modified Dose Response (MDR) model described the ammonium exchange behavior better than the Thomas and the Bohart-Adams models. Then, a design flow of the ion exchange reactor was constructed by correlating constants in the MDR model with engineering parameters, and the ion exchange reactor was designed for continuous operation of the CAIR system. The average concentrations of chemical oxygen demand, total phosphorus, ammonium nitrogen, and total nitrogen in the effluent of the CAIR system were 7.22 ± 2.26, 0.17 ± 0.05, 1.49 ± 0.01, and 1.62 ± 0.02 mg/L, respectively. The almost unchanged exchange capacity and physicochemical properties after the multicycle operation confirmed the durability of zeolite for ion exchange. Techno-economic analysis suggested that the CAIR system is practically promising for stormwater management with efficient pollutants removal, small footprint, and acceptable operating cost.

Effect of Suspended Solids and Organic Matter in Water on the Removal of ZnO-NPs by Coagulation

Background: Zinc oxide nanoparticles (ZnO-NPs) have been shown to have a non-negligible impact on the environment Objective: Kaolin and humic acid were used in the aqueous environment to study their effects on the removal of ZnO-NPs. Method: In this work, polyaluminum ferric chloride (PAFC)/cationic polyacrylamide (CPAM) coagulants were used together with kaolin and humic acid were used to study their effects on the removal of ZnO-NPs and to analyze their mechanism of action. Results: The results showed that the removal rate of ZnO-NPs in the humic acid system decreased by about 30% compared to that in the pure water system, and increasing the ionic strength and humic acid concentration was not conducive to removing ZnO-NPs. On the other hand, the ZnO-NPs removal rate in the kaolin system was up to 96.28%, and increasing the ionic strength and kaolin concentration contributed to the removal of ZnO-NPs. In the humic acid and kaolin systems, the effects of coagulant dosage and pH on the removal of ZnO-NPs were about the same as in the pure water system. Moreover, 5 mg/L humic acid inhibited floc growth during removal of ZnO-NPs by coagulation with PAFC/CPAM. In contrast, 5 mg/L kaolin promoted flocs growth, resulting in stronger and more stable flocs and a 5.25% increase in the fractal dimension compared to the pure water system. Conclusion: These results suggested that suspended solids and natural organic matter in the water could directly affect the effectiveness of coagulation to remove ZnO-NPs.

Red mud-based polyaluminium ferric chloride flocculant: Preparation, characterisation, and flocculation performance

In this study, red mud was used as a raw material to extract Al and Fe using hydrochloric acid. A highly efficient polyaluminium ferric chloride (PAFC) flocculant was prepared by adjusting the pH of a leaching solution, the molar ratio of Al to Fe, and the polymerisation temperature. The effects of synthesis and flocculation conditions on the flocculation performance of aged landfill leachate were investigated. The results confirmed that PAFC flocculant prepared at a polymerisation pH of 2.5, Al/Fe molar ratio of 8, and polymerisation​ temperature of 70 °C had the optimum effect. The effect of PAFC and commercial polyaluminium ferric chloride flocculants used under different flocculation conditions were compared. The chemical oxygen demand, UV 254 , chroma, total organic carbon, and PAFC settlement height at a flocculant concentration of 1.2 g/L and solution pH of 6 were 72.2%, 79.2%, 82.9%, 82.6%, and 9.5 cm (within 90 min), respectively. The PAFC performed excellently at flocculation and can be used as a simple and potentially low-cost wastewater treatment agent in industrial applications. • Red mud was used to synthesise polyaluminium ferric chloride (PAFC) flocculant. • The COD and TOC of PAFC to landfill leachate were 72.2% and 82.6%, respectively. • PAFC have advantages over commercial PAFC in settlement velocity and TOC removal efficiency.

Preparation of Poly Aluminum-Ferric Chloride (PAFC) Coagulant by Extracting Aluminum and Iron Ions from High Iron Content Coal Gangue.

Poly aluminum-ferric Chloride (PAFC) is a new type of high efficiency coagulant. In this study, high iron type gangue is used as a main raw material. It is calcined at 675 °C for 1 h and 3% CaF2 is added to the calcined powder and reacted with 20% hydrochloric acid at 93 °C for 4 h. The leaching ratio of aluminum ions is 90% and that of iron ions is 91%. After Fe2+ ions are oxidized in the filtrate, CaCO3 is used to adjust the pH of the filtrate to 0.7. The microwave power is adjusted to 80 W and the filtrate is radiated for 5 min. After being aged for 24 h, PAFC product is obtained. The prepared PAFC is used to treat mine water and compared with the results of PAC and PAF, the turbidity removal ratio of PAFC is 99.6%, which is greater than 96.4% of PAC and 93.7% of PAF. PAFC is a mixture with different degrees of polymerization. It demonstrates that extracting aluminum and iron ions from high iron content gangue to prepare PAFC by microwave is efficient and feasible.

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.