Environmental Science-Water Research & Technology
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2023
·Vol. 10
·期 2
·431-441
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IF 5
Jun Guo,Xia Xu,Shiyao Bu,Ruoying Yang,Yingang Xue,Qiuya Zhang,Mingguo Peng
The use of efficient modification methods determines the wide application potential of zirconium salt coagulants. In this study, zirconium xerogel coagulants were prepared by acetylacetone regulation, and they exhibited application potential in a wider range of pH (pH = 5–9) and higher coagulation performance (residual turbidity < 2 NTU) than ZrCl4 and PAC at a dosage of 0.2 mM. In addition, the acetylacetone-regulated xerogel coagulants were insensitive to changes in organic matter and were effective in removing turbidity even at high organic matter concentrations. The interaction mechanism between the zirconium xerogel coagulants and humic acid involving a complexation effect in the acidic environment and a sweeping effect in the alkaline environment has been proposed. The interpretation of this mechanism further revealed the “protective umbrella effect” of acetylacetone, which might work as a hydrolysis inhibitor to reduce the hydrolysis rate, as a chelating ligand to control the release of H+, and as a barrier to prevent organic matter from coming into direct contact with metal ions. These characteristics provide better stability, a higher effluent pH and higher turbidity removal. This study outlines the interaction mechanism of zirconium xerogel coagulants with humic acid and provides evidence for the contribution of acetylacetone in fabricating efficient gel coagulants.
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CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Yuanbo Zhang,Jiamei Xu,Jicheng Liu,Kun Lin,Zijian Su
Secondary aluminum dross (SAD) is a kind of hazardous waste with high aluminum content produced in the aluminum industry. From another point, SAD is also considered as a valuable aluminum resource, which can be used as high-quality raw material for value-added products such as refractory materials . In this study, a novel route for preparing corundum-spinel heat storage spheres (HSS) using washed residue of secondary aluminum dross (WSAD) as the main raw material was proposed. FactSage 8.1 software was used for the detailed thermodynamic calculation, which provided accurate theoretical guidance for the actual synthesis experiments. The effects of roasting temperature and formula on the main phases, compressive strength , porosity, and bulk density of HSS were systematically analyzed. The strengthening mechanism of the liquid phase on the sintering strength was revealed. The results showed that the HSS with good properties could be obtained with 90 wt% WSAD, 10 wt% kaolin, and 1 wt% bentonite. The HSS mainly consisted of corundum and spinel phases. The synthetic temperature of corundum-spinel ceramic was reduced by more than 200 °C. This study provides a novel way for value-added utilization of SAD as well as realizing the deep detoxification and the removal of nitrogen of it.
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INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2023
·
IF 8.2
Danting Sun,Jia Zeng,Dongjie Yang,Xueqing Qiu,Weifeng Liu
Flocculation is a common process for wastewater treatment. However, the most commonly used organic synthetic flocculants such as polyacrylamide are petroleum-based. In this work, biomass lignin was grafted with cationic starch to synthesize low-cost, green and fully biomass-based multifunctional flocculants. The cationic polyacrylamide was replaced by cheap industrial cationic starch. Hyperbranched multifunctional lignin-grafted cationic starch flocculant (CS-L) was successfully prepared via ring-opening reaction with epichlorohydrin. The mass content of lignin in the grafted product was between 16.6 % and 70.1 %. With the dosage of CS-L between 4.0 and 7.5 mg/l, the turbidity removal rate for 500 mg/l kaolin suspension reached more than 97 %. When the dosage of CS-L was 24 mg/l, the removal rate of 50 mg/l Cu 2+ reached 85.7 %. Importantly, when the mixed solution of kaolin particles and Cu 2+ was treated, the synchronous removal rates of kaolin and Cu 2+ reached 90 % and 72 % respectively in the range of 8.0–12.0 mg/l flocculant addition. The synthesized lignin-grafted cationic starch flocculant showed an excellent multifunctional flocculation function.
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PubMed
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SCIENCE OF THE TOTAL ENVIRONMENT
·
2023
·
IF 9.8
Wei Gao,Aoyun Mo,Jie Jiang,Yuqing Liang,Xiaomu Cao,Defu He
Microplastics (MPs) pose a potential risk to aquatic ecosystems , and there is a growing demand to alleviate the contamination of MPs. Here, we introduce cationic-modified starch (CS) as an eco-friendly bio-coagulant for removing MPs from water. CS with varying degrees of substitution was synthesized and characterized, and its performance in removing MPs was evaluated under different MP sizes, types, and aging, as well as various water conditions. The results indicated that CS efficiently removed MPs, achieving an average removal rate of 65.33 % for polystyrene particles, with higher removal rates for larger, high-density, and aged MPs. The efficiency of CS remained consistent across a wide range of water pH values, but was significantly reduced in the presence of kaolin clay or/and humic acid . The removal efficiency of CS for MPs was enhanced by the non-ionic surfactant, Tween 20, but inhibited by the anionic surfactant, cetyltrimethylammonium bromide. In addition, CS could concurrently remove both MPs and phenanthrene , as a typical water contaminant. Moreover, the applicability of CS was demonstrated in natural water samples from the Ecological Demonstration Zone of the Yangtze River Delta, China, with an average removal rate of 60.13 ± 3.15 %. Taken together, this study offers an environmentally friendly and cost-effective approach for the removal of MPs from water, demonstrating CS has significant application potential as a sustainable solution to mitigate microplastic pollution.
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ENERGY & FUELS
·
2021
·
IF 3.605
Hailing Sun,Liyuan Cao,Yuhao Zhang,Liang Zhao,Jinsen Gao,Chunming Xu
The effect of acid concentration and reaction temperature on the reaction of 1-hexene cracking to propylene was investigated. The catalysts with different acid concentrations were prepared by the alkali ion and phosphorus modification of ZSM-5 zeolite. It was observed that both decreasing the concentration of strong Brønsted acid sites (SBASs) and increasing reaction temperatures can enhance the selectivity and yield of propylene and hinder the formation of side products including hydrogen, C1∼C5 alkanes, aromatics, and coke. The hydrogen transfer reaction had an important effect on the selectivity of C3∼C5 olefins in the high concentration of SBASs. Besides, high temperatures intensified monomolecular reactions and hindered bimolecular or multimolecular reactions.On the basis of product distributions, possible main and side reaction routes were summarized under the real industrial reaction conditions. The conclusion was significant to optimize the catalyst design of olefin cracking or pyrolysis processes and operation conditions for increasing the yield of propylene.
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Journal of Environmental Sciences
·
2021
·
IF 5.565
Xueyi Dong,Xihua Cao,Wenbin Jiang,Xiuxian Song,Zhiming Yu,Shitao Yu
Polyaluminum chloride modified clay (PAC-MC) is a safe and efficient red tide control agent that has been studied and applied worldwide. Although it is well known that the distribution of hydrolytic aluminum species in PAC affects its flocculation , little is known about the influence of particulars aluminum species on the microalgae removal efficiency of PAC-MC; this lack of knowledge creates a bottleneck in the development of more efficient MCs based on aluminum salts. The ferron method was used in this study to quantitatively analyze the distributions of and variations in different hydrolytic aluminum species during the process of microalgae removal by PAC-MC. The results showed that Al a , which made up 5%–20% of the total aluminum, and Al p , which made up 15%–55% of the total aluminum, significantly affected microalgae removal, with Pearson's correlation coefficients of 0.83 and 0.89, respectively. Most of the aluminum in the PAC-MC sank rapidly into the sediments, but the rate and velocity of settlement were affected by the dose of modified clay. The optimal dose of PAC-MC for precipitating microalgae was determined based on its aluminum profile. These results provide guidance for the precise application of PAC-MC in the control of harmful algal blooms .
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ADSORPTION SCIENCE & TECHNOLOGY
·
2021
·
IF 4.232
Shunyu Huang,Jingji Li,Jipeng Wang
Soil leucine aminopeptidase (LAP) is a hydrolytic enzyme involved in the acquisition of nitrogen by microorganisms. In contaminated soils, LAP activity is affected not only by the type and concentration of heavy metals but also by the form of enzyme. Here, we investigated the degree and mechanism of cadmium (Cd) inhibition of soil LAP and purified LAP. We also examined the effect of montmorillonite and kaolinite on LAP and LAP contaminated with Cd. The results showed that Cd inhibition of LAP activity increased with increasing Cd concentration and that Cd exerted noncompetitive inhibition of LAP. The addition of clay minerals decreases LAP activity and the maximum reaction rate (), regardless of the presence of Cd. Montmorillonite decreases the affinity of LAP to the substrate (), while kaolinite increases the affinity of LAP to the substrate. The clay mineral-immobilized LAP showed an increase in resistance to Cd contamination compared with the free LAP. The results obtained in this study may aid in understanding the toxic effects of heavy metals on soil enzymes.
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CELLULOSE
·
2021
·Vol. 28
·期 17
·11097-11108
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IF 5.044
Li Zhen,Gong Wenli,Chen Xuan,Liu Lin,Meng Ranju,Ding Yanhong,Yao Juming
Green bio-flocculants from renewable biomass resources have received the widespread attention for wastewater treatment, which are promising alternatives to petroleum-based synthetic flocculants. In this paper, sustainable cationic cellulose bio-flocculants with various amino group contents were successfully prepared by a feasible chemical crosslinking with polyethyleneimine (PEI). The flocculation performances of diverse PEI-grafting cellulose (CE-PEI) were evaluated to purify turbid Kaolin suspension. Further, the flocculation kinetics and flocculation mechanism were investigated. Benefiting from the high surface positive charges and supramolecular structure, CE-PEI bio-flocculants with amino group contents of 17.5 mmol/g displayed the best turbidity removal efficiency. The residual turbidity of Kaolin suspension decreased from the initial 480–8.6 NTU, a 98.2% reduction with CE-PEI dosage of 0.15 mg/mL, sedimentation time of 30 min at pH 7.0. Flocculation kinetic results indicated that interaction of aggregation and collision between CE-PEI bio-flocculants and Kaolin particles was sufficient for the flocculation process at the optimal CE-PEI dosage. Moreover, charge neutralization was the dominant mechanism for the flocculation of CE-PEI on Kaolin. Thus, this work not only exploits a promising application of cellulose as a bio-flocculant, but also provides a feasible approach to efficiently purify high turbidity wastewater. Graphic abstract
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POLYMER
·
2021
·
IF 4.43
Hongxiang Ou,Jiacheng Xu,Ben Liu,Honglai Xue,Yunxuan Weng,Juncheng Jiang,Guoguang Xu
To improve the flame retardancy of low density polyethylene (LDPE), the intercalation of modified kaolin with urea (KU) was prepared by mechanochemical method and combined with intumescent flame retardant (IFR) as LDPE flame retardant in this paper. KU was used as synergistic flame retardant. The mechanical properties , flame retardant properties and smoke properties of KU/SiO 2 @MAPP/DPER/LDPE composites were investigated. The results demonstrated that the intercalation rate of KU was 63% and the addition of KU effectively improved many aspects of LDPE's performance. When 3 wt% KU were added, the LOI of SiO 2 @MAPP/DPER/LDPE increased from 24.1% to 27.2% and the UL-94 reached V-1. The tensile strength was 16.6 MPa and the elongation at break was 554%. The smoke density test showed that the flue gas emission was obviously improved. Raman test showed that the R value of LDPE3 was 0.96. The addition of KU effectively increased the residual carbon content of composites and thermal stability of the composites.
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Journal of Magnesium and Alloys
·
2021
·
IF 10.088
Xiang Liu,Tian C. Zhang,Yuxin Zhang,Jinsong Rao,Shaojun Yuan
Superhydrophobic coating has been widely studied for its great applicational potential, such as for corrosion protection of magnesium alloys while it has been restrained by expensive materials, sophisticated preparation process and infirm rough structures. In this study, the electrochemical method was adopted by using a two-electrode system for rapid hydrophobic modification to obtain superhydrophobic kaolin. By mixing the modified superhydrophobic kaolin with commercial epoxy resin and polydimethylsiloxane glue, a paint can be formed and easily used on various substrates for preparation of superhydrophobic coating via spraying method. The influence factors on wettability of the modified kaolin and the mixing ratio of each component of the coating were explored. Also, the wettability, durability and anticorrosion of the prepared coating were evaluated comprehensively. The coating was able to maintain superhydrophobic after immersed in HCl solution at pH 1, the NaOH solution at pH 14, and 3.5 wt.% NaCl solution for 16, 21, 30 days, respectively. In addition, the coating exhibited 4A grade adhesion, high hydrophobicity after abraded for 200 cycles on a 600-mesh sandpaper with 100 g weight, and 99.86% anticorrosion efficiency after soaked in 3.5 wt.% NaCl solution for 20 days, demonstrating a good robustness and anti-corrosion property. Furthermore, the coating showed good transparency, flexibility and was easy to make in a large scale by the spraying method, which is of great significance to promote the practical application of superhydrophobic coatings and the anticorrosion Mg alloys.
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IRANIAN POLYMER JOURNAL
·
2021
·Vol. 30
·期 7
·675-683
·
IF 1.899
Wei Liu,Jinju Ma,Hongjian Pang,Zongwu Wang,Xinding Yao
A degradable flocculant was prepared by natural renewable products (starch) and a cationic polymer. A cationic polyamine polymer was prepared by reaction of bis(hexamethylene)triamine with epichlorohydrin. The influence of substrate ratio and molecular weight of cationic polymer on flocculation was investigated and the optimum molecular weight was about 4000. Polyamine-modified starch flocculant was prepared by etherification reaction of cationic polyamine polymer and corn starch. The influence of substitution degree (DS) of starch on flocculation was investigated and the maximum DS was 0.18. The structure of starch-modified flocculant was characterized by XRD and the results confirmed that the plasticized samples contained some crystalline structures that were not destroyed by the etherification reaction process and some newly formed V-type crystalline structures were mainly induced by processing. Flocculation performance was evaluated in simulated kaolin suspension and was compared with that of commercial cationic polyacrylamide (CPAM) and polyaluminium chloride (PAC) flocculants. The flocculation effects of polyamine-modified starch flocculants and commercial flocculants under different dosages and pH values were compared. The results showed that the starch-modified flocculant had the best effect and the cationic starch derivatives flocculation performance increased with increasing DS, and exhibited steady flocculation performance to kaolin suspension in the broad pH range from 4 to 10. The preparation method of starch-modified flocculant is simple in preparation process, low in production cost and pollution-free, and facilitates industrial production.
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FIBERS AND POLYMERS
·
2021
·Vol. 22
·期 6
·1518-1525
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IF 2.153
Chen Chaoying,Zhang Xiumei,Deb Hridam,Liang Fugen,Zhu Haidong,Cui Kecong,Zhang Yong,Yao Juming
Flocculation is the first and important step to remove suspended and slightly soluble pollutants in industrial wastewater treatment. Flocculant is just the key element for flocculation process. Polyacrylamide (PAM) is the most widely used flocculant. But it still holds some potential flaws which are ignored by people. An eco-friendly bamboo cellulose-grafted-ployacrylamide flocculant (BC-g-PAM) was then synthesized by free-radical graft copolymerization in homogeneous aqueous solution. The optimal synthesis conditions of the BC-g-PAM was investigated. FTIR, TG, XRD and FESEM were employed to characterize and define its molecular structure and physical characteristics. The BC-g-PAM was also adopted to treat an actual papermaking wastewater. The positive results showed that the BC-g-PAM exhibited an excellent flocculation performance on the papermaking wastewater. The average turbidity removal rate reached 99.7 % and related suspended solids exhibited the corresponding decline. This flocculation also caused a positive effect on the reduction of COD Cr and BOD 5 of the wastewater. Meanwhile, the BC-g-PAM exhibited an excellent biodegradability. Its degradation rate reached 63.4 % at 90 d in soil extracting solution.
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