, Aging of nZVI-Ca(OH) 2 particles was carried out in the air at room temperature

, At certain intervals (5 d, 10 d, 20 d and 30 d), 100 mg of aged samples were collected

, Energy dispersive X-ray 150 spectroscopy (EDS) was coupled with SEM to examine the element on the particle 151 surface. The mass ratio of Ca(OH) 2 in the composite of nZVI-Ca(OH) 2 was measured 152 by analyzing the Fe and Ca concentration in acid-digestion solution of nZVI-Ca(OH) 2 153 with Atomic Absorption Spectrophotometer (AAS, PEAA700). The crystalline phases 154 were identified with an X-ray diffractometer (XRD, Philips Electronic Instruments). the Ca(OH) 2 shell, The morphological images of nZVI-Ca(OH) 2 particles were recorded with a 149 scanning electron microscope (SEM

, As observed, there is a strong peak at 44.5° which should be assigned to Fe 166 (0) [29, 30], while no obvious peaks of Ca(OH) 2 were found. Similar phenomena 167 were also reported in other studies [23, 31], in which XRD was used to characterize 168 surface coated nZVI with Ca(OH) 2 and Al(OH) 3, The chemical components of nZVI-Ca(OH) 2 were characterized by the XRD 165 (Fig. 1c)

. Ca, OH) 2 nor Al(OH) 3 was observed. This might be due to their low concentrations or 170 low degree of crystallinity

, In order to figure out the Ca(OH) 2 content coated on nZVI, AAS was used to 172 determine the ratio of Fe and Ca after acid digestion of the nZVI-Ca

, It is clear that the sonication time did significantly affect the 175 coating thickness. The amount of Ca(OH) 2 was 1.31% of the total weight after 0.5 h 176 coating, which rose to 10.19% after 4 h coating. To verify the effect of Ca(OH) 2 177 coating on the mobility of nZVI particles, a simplified sand column test was carried 178 out and the results show that the Ca(OH) 2 coating did improve the transport of nZVI 179 particles in porous media, composites. Fig. 1d shows the content of Ca(OH) 2 coated on the nZVI particles under 174 different sonication time

, However, no obvious difference was observed for the nZVI-Ca(OH) 2 with 181 different amount of Ca(OH) 2 (data not shown). In view of the effect of sonication time 10

, As mentioned above, the sonication time during synthesis can affect the 189 percentage of Ca(OH) 2 on nZVI-Ca(OH) 2 particle surface. It could possibly be a 190 critical factor in SMT removal by nZVI-Ca(OH) 2 activated persulfate. Thus, effect of 191 sonication time on SMT removal was investigated (Fig. 2). As observed, both removal 192 efficiency and reaction rates of SMT

C. The, OH) 2 coating thickness on nZVI surface, it seems had little influence on SMT 196 removal in persulfate system. Since 0.5 h sonication time was long enough to give an 197 excellent performance in SMT removal for nZVI-Ca(OH) 2 , it was selected for the

, As shown in Fig. 3a, the final removal efficiency as well as the removal 11 mechanism, the changes of pH during reaction were monitored, SMT removal experiments were carried out at four different initial pH values, i.e. 3, 5, 201 7 and 9

, min) to around 3.5 and finally maintained in a very narrow pH range of 3.0 206 to 3.2. This should be the reason for the similar SMT removal under various pH 207 conditions. The sharp pH change may, matter at what initial pH value, the solution pH dropped dramatically 205

. Ca, OH) 2 layer would consume protons and then cause a rise in solution pH (Eq. 9), 211 the mass ratio of Ca(OH) 2 is extremely low (1.31%), the influence of Ca(OH) 2 layer last two decades, Water research, vol.75, pp.224-248, 1994.

T. Phenrat and I. Kumloet, Electromagnetic induction of nanoscale zerovalent iron 349 particles accelerates the degradation of chlorinated dense non-aqueous phase liquid: 350 Proof of concept, Water research, vol.107, pp.19-28, 2016.

H. R. Dong, L. Li, Y. Lu, Y. Cheng, Y. Wang et al.,

. Zeng, Integration of nanoscale zero-valent iron and functional anaerobic bacteria for 353 groundwater remediation: A review, Environment International, vol.124, pp.265-277, 2019.

Y. J. Cheng, H. Dong, Y. Lu, K. Hou, Y. Wang et al.,

G. Zhang and . Zeng, Toxicity of sulfide-modified nanoscale zero-valent iron to 356 Escherichia coli in aqueous solutions, Chemosphere, vol.220, pp.523-530, 2019.

L. J. Kong, Y. Zhu, M. Liu, X. Chang, Y. Xiong et al., Conversion of Fe-358 rich waste sludge into nano-flake Fe-SC hybrid Fenton-like catalyst for degradation of 359 AOII, Environmental Pollution, vol.216, pp.568-574, 2016.

I. Mikhailov, S. Komarov, V. Levina, A. Gusev, J. P. Issi et al., 361 Nanosized zero-valent iron as Fenton-like reagent for ultrasonic-assisted leaching of 362 zinc from blast furnace sludge, Journal of hazardous materials, vol.321, pp.557-565, 2017.

H. Dong, Q. He, G. Zeng, L. Tang, L. Zhang et al., 364 Degradation of trichloroethene by nanoscale zero-valent iron (nZVI) and nZVI 365 activated persulfate in the absence and presence of EDTA, Chemical Engineering 366 Journal, pp.410-418, 2017.

N. Barhoumi, N. Oturan, H. Olvera-vargas, E. Brillas, A. Gadri et al.,

. Oturan, Pyrite as a sustainable catalyst in electro-Fenton process for improving 369 oxidation of sulfamethazine. Kinetics, mechanism and toxicity assessment, Water, vol.370, pp.52-61, 2016.

J. Yan, H. Lu, W. Gao, X. Song, and M. Chen, Biochar supported nanoscale 372 zerovalent iron composite used as persulfate activator for removing trichloroethylene, Bioresource technology, vol.373, pp.269-274, 2015.

H. R. Dong, Y. Cheng, Y. Lu, K. Hou, L. Zhang et al.,

G. Ning and . Zeng, Comparison of toxicity of Fe/Ni and starch-stabilized Fe/Ni 376 nanoparticles toward Escherichia coli. Separation and Purification Technology, vol.210, pp.504-510, 2019.

C. Kim, J. Y. Ahn, T. Y. Kim, W. S. Shin, and I. Hwang, Activation of Persulfate by 379 Nanosized Zero-valent Iron (NZVI): Mechanisms and Transformation Products of 380 NZVI, Environmental science & technology, vol.52, pp.3625-3633, 2018.

H. Dong, Y. Xie, G. Zeng, L. Tang, J. Liang et al., 382 The dual effects of carboxymethyl cellulose on the colloidal stability and toxicity of 383 nanoscale zero-valent iron, Chemosphere, vol.144, pp.1682-1689, 2016.

P. Tanapon, S. Navid, S. Kevin, R. D. Tilton, and G. V. Lowry, Aggregation and 385 sedimentation of aqueous nanoscale zerovalent iron dispersions, Environmental 386 science & technology, vol.41, pp.284-290, 2007.

X. Q. Li, D. W. Elliott, and W. X. Zhang, Zero-Valent Iron Nanoparticles for 388 Abatement of Environmental Pollutants: Materials and Engineering Aspects, Critical, vol.20

, Reviews in Solid State & Materials Sciences, vol.31, pp.111-122, 2006.

H. Dong, J. Deng, Y. Xie, C. Zhang, Z. Jiang et al., 391 Stabilization of nanoscale zero-valent iron (nZVI) with modified biochar for Cr(VI) 392 removal from aqueous solution, Journal of hazardous materials, vol.332, pp.79-86, 2017.

Y. Zhang, Y. Li, J. Li, G. Sheng, Z. Yun et al., Enhanced Cr(VI) removal by 394 using the mixture of pillared bentonite and zero-valent iron, Chemical Engineering 395 Journal, pp.243-249, 2012.

L. Changha and D. L. Sedlak, Enhanced formation of oxidants from bimetallic 397 nickel-iron nanoparticles in the presence of oxygen, Environmental science & 398 technology, vol.42, pp.8528-8533, 2008.

H. L. Lien and W. X. Zhang, Nanoscale Pd/Fe bimetallic particles: Catalytic effects of 400 palladium on hydrodechlorination, Applied Catalysis B Environmental, p.77, 2007.

H. Dong, C. Zhang, K. Hou, Y. Cheng, J. Deng et al., 403 Removal of trichloroethylene by biochar supported nanoscale zero-valent iron in 404 aqueous solution, Separation and Purification Technology, vol.188, pp.188-196, 2017.

O. S. Arvaniti, Reductive Degradation of Perfluorinated Compounds in Water 406 using Mg-aminoclay coated Nanoscale Zero Valent Iron, Chemical Engineering 407 Journal, vol.262, pp.133-139, 2015.

H. R. Dong, Q. He, G. M. Zeng, L. Tang, C. Zhang et al., Chromate removal by surface-modified nanoscale zero-valent iron: Effect of 21 410 different surface coatings and water chemistry, Journal of Colloid and Interface, vol.411, pp.7-13, 2016.

. Dong, . Hr;-hou, . Kj;-qiao, Y. Ww;-cheng, L. Zhang et al., , p.413

Q. Ning and G. M. Zeng, Insights into enhanced removal of TCE utilizing sulfide-414 modified nanoscale zero-valent iron activated persulfate, Chemical Engineering 415 Journal, vol.359, pp.1046-1055, 2019.

W. Cai-jie and L. Xiao-yan, Surface coating with Ca(OH)2 for improvement of the 417 transport of nanoscale zero-valent iron (nZVI) in porous media, Water Science &

, Technology A Journal of the International Association on Water Pollution Research, vol.419, p.2287, 2013.

Y. G. Kang, H. Yoon, W. Lee, E. J. Kim, and Y. S. Chang, Comparative study of 421 peroxide oxidants activated by nZVI: Removal of 1,4-Dioxane and arsenic(III) in 422 contaminated waters, Chemical Engineering Journal, vol.334, pp.2511-2519, 2018.

Y. Gao, N. Gao, Y. Deng, Y. Yang, and Y. Ma, Ultraviolet (UV) light-424 activated persulfate oxidation of sulfamethazine in water, Chemical Engineering 425 Journal, pp.248-253, 2012.

Y. Fan, Y. Ji, D. Kong, J. Lu, and Q. Zhou, Kinetic and mechanistic investigations of 427 the degradation of sulfamethazine in heat-activated persulfate oxidation process, Journal of hazardous materials, vol.428, pp.39-47, 2015.

Y. Xie, H. Dong, G. Zeng, L. Zhang, Y. Cheng et al.,

. Deng, The comparison of Se(IV) and Se(VI) sequestration by nanoscale zero-valent 22

, 431 iron in aqueous solutions: The roles of solution chemistry, Journal of hazardous 432 materials, vol.338, pp.306-312, 2017.

J. Deng, H. Dong, C. Zhang, Z. Jiang, Y. Cheng et al., 434 Nanoscale zero-valent iron/biochar composite as an activator for Fenton-like removal 435 of sulfamethazine, Separation and Purification Technology, vol.202, pp.130-137, 2018.

H. Dong, Z. Jiang, J. Deng, C. Zhang, Y. Cheng et al.,

. Zeng, Physicochemical transformation of Fe/Ni bimetallic nanoparticles during aging 438 in simulated groundwater and the consequent effect on contaminant removal, Water, vol.439, pp.51-57, 2017.

H. Dong, C. Zhang, J. Deng, Z. Jiang, L. Zhang et al.,

. Zeng, Factors influencing degradation of trichloroethylene by sulfide-modified 442 nanoscale zero-valent iron in aqueous solution, Water research, vol.135, pp.1-10, 2018.

Y. B. Hu and X. Y. Li, Influence of a thin aluminum hydroxide coating layer on the 444 suspension stability and reductive reactivity of nanoscale zero-valent iron, pp.554-564, 2018.

H. Li, J. Wan, Y. Ma, Y. Wang, and M. Huang, Influence of particle size of zero-7, Chemical Engineering Journal, vol.237, pp.487-496, 2014.

J. Deng, Y. Shao, N. Gao, Y. Deng, C. Tan et al., Zero-valent
URL : https://hal.archives-ouvertes.fr/hal-02278404

, iron/persulfate(Fe 0 /PS) oxidation acetaminophen in water, International Journal of 451 Environmental Science & Technology, vol.11, issue.23, pp.881-890, 2014.

H. J. Fan, S. T. Huang, W. H. Chung, J. L. Jan, W. Y. Lin et al., Degradation 453 pathways of crystal violet by Fenton and Fenton-like systems: Condition optimization 454 and intermediate separation and identification, Journal of hazardous materials, vol.171, pp.1032-1044, 2009.

O. Seok-young, K. Hyeong-woo, P. Jun-mo, P. Hung-suck, and Y. Chohee, 457 Oxidation of polyvinyl alcohol by persulfate activated with heat, Fe2+, and zero-458 valent iron, Journal of hazardous materials, vol.168, pp.346-351, 2009.

Y. X. Pang, Y. Ruan, Y. Feng, Z. Diao, K. Shih et al., 460 Ultrasound assisted zero valent iron corrosion for peroxymonosulfate activation for 461 Rhodamine-B degradation, Chemosphere, vol.228, pp.412-417, 2019.

L. W. Matzek and K. E. Carter, Sustained persulfate activation using solid iron: 463 kinetics and application to ciprofloxacin degradation, Chemical Engineering Journal, vol.464, pp.650-660, 2017.

H. Dong, B. Wang, L. Li, Y. Wang, Q. Ning et al.,

, Activation of persulfate and hydrogen peroxide by using sulfide-modified nanoscale 467 zero-valent iron for oxidative degradation of sulfamethazine: A comparative study

, Separation and Purification Technology, vol.218, pp.113-119, 2019.

S. Bae, R. N. Collins, T. D. Waite, and K. Hanna, Advances in surface passivation of 470 nanoscale zerovalent iron (NZVI): A critical review, Environmental science & 471 technology, vol.52, pp.12010-12025, 2018.

Y. H. Jo, S. H. Do, and S. H. Kong, Persulfate activation by iron oxide-immobilized