Co-Ni LDHs/PES Hybrid Membrane Synergizes With PMS to Effectively Degrade Orange ฀

: The Co-Ni layered double hydroxides (Co-Ni LDHs) were prepared using co- 9 precipitation method and Co-Ni LDHs hybrid polyethersulfone membranes (Co-Ni LDHs/PES) 10 were prepared by phase inversion method, respectively. The products were characterized by FT-IR, 11 XRD, SEM, TEM, EDX, TGA and tensile strength test. Results showed that the Co-Ni LDHs/PES 12 membranes as prepared had excellent mechanical properties. The decrease of membrane contact 13 angle and the increase of membrane water flux indicated that the hydrophilicity of Co-Ni LDHs/PES 14 membrane can be improved. The hybrid membranes showed a good catalytic performance. As the 15 loading of LDHs was 5mg·L -1 , the dosage of PMS and AO7 was 1mmol·L -1 and 0.05mmol·L -1 , 16 respectively, the degradation rate of AO7 can reach 96.58% within 20 minutes. The ion leaching of 17 Co-Ni LDHs/PES was much less than that of Co-Ni LDHs, so, the dosage of the Co-Ni LDHs was 18 much less than of Co-Ni LDHs. After repeated used for four times, Co-Ni LDHs/PES still has good 19 catalytic performance. The effects of Co-Ni LDHs dosage, PMS dosage, initial pH, Cl - and HA on 20 the degradation of AO7 were investigated. The catalytic degradation mechanism of Co-Ni 21 LDHs/PES was studied by free radical quenching experiments and XPS analysis. The main active 22 species in the catalytic oxidation system are SO 4·- ,·OH, 1 O 2 and O 2·- , among which 1 O 2 and O 2·- 23 were the main active species.


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The azo bond and amino group in azo dyes increase the harmful properties of compounds to Si grafted PAN film, which has good storage capacity and repeatable catalytic activity (Li et al. 64 2021b). Subsequently, inorganic nanoparticles have molecular sieving and catalytic properties, and 65 organic polymers have mechanical and processing properties, they further enhance the water flux 66 and selectivity of the catalytic membrane, reduce the fouling tendency of the membrane fouling, 67 and enhance the self-cleaning ability of the membrane (Yi et al. 2011). For example, Kang et al. 68 used chelation assisted in-situ growth to prepare LDHs/PAN, which can be effectively used for 69 desalination in textile wastewater (Kang et al. 2020 The angle between the droplet and the surface was measured after 5s (Ganjali et al. 2020); According 152 to ASTM D412 standard, the mechanical properties of LDHs/PES were studied by using Zwick 153 tensile testing machine (GT-Al-3000, Germany). The effective length of 5cm and width of 1.5cm 154 were prepared, the elongation was measured at 10mm·min -1 at room temperature. The miscibility   The XRD pattern of Co-Ni LDHs was shown in Fig.2a

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The morphology and structure of all samples were characterized by SEM and TEM. As structure. Except for a few aggregated nanoparticles, the lamellar particles had no obvious change.

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The SAED was 0.203nm. It can be seen from SAED that the formation of the diffraction ring was 195 attributed to the crystal structure of LDHs, the fuzzy dispersion of the diffraction ring indicated that 196 the crystallinity was low, which also indicates that there were some defects in LDHs, which is   The increase of hydrophilicity provides better antifouling performance. The pure water layer 226 formed on the super hydrophilic surface can prevent the adsorption and deposition of hydrophobic 227 pollutants on the membrane. When the increase of LDHs was 6.98wt%, the film contact angle was 228 from 87.9° to 53.42° (Fig.5a). The cross-flow filtration device was used to test the membrane sample.

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The membrane sample to be tested was cut into a 50mm disc and embedded in the membrane pool.

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The effective test area of the membrane was 20.25 cm 2 . With deionized water as the filtrate, the 231 quality of permeated water in the inner membrane was tested after preloading for 30min under 232 0.2MPa transmembrane pressure (Ye et al. 2021) (Fig.5b). The results showed that the pure water 233 flux of blank membrane was 66.89L·m -2 h -1 , and the pure water permeability of catalytic membrane 234 was 86.884L·m -2 h -1 , 125.776L·m -2 h -1 , 178.774L·m -2 h -1 , 158.932L·m -2 h -1 . From the above analyses, 235 we can get the results that the surface wettability of the membrane increases with the increase of the     There is a clear relationship between the mechanical properties of the membrane and the 277 durability of the membranes used for pressure driven filtration. Therefore, the typical mechanical 278 properties of the prepared films, including tensile strength, were calculated and listed in Table 4.

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Compared with the membrane without nano fillers, it was found that the mechanical standard of the of LDHs content from 1.23wt% to 6.98wt%, which can be described by the aggregation of LDHs.
287 The TGA results (Fig.7) showed that the blank membrane and catalytic membrane showed a   Co-Ni LDHs/PES synergized with PMS to degrade AO7 to evaluate the catalytic behavior of 307 the catalytic membrane. As shown in Fig.8a, the removal rates of catalyst, blank membrane and 308 catalytic membrane were 6.32%, 43.55% and 48.95% respectively after 20min of reaction. The 309 removal rates of blank membrane and catalytic membrane doped with Co-Ni LDHs did not change 310 significantly. The Co-Ni LDHs and PES membranes showed a rather limited role in the physical 311 adsorption process. When the addition of PMS was 1mmol·L -1 , the removal rate of AO7 reached 312 13.06% after 20min; the results showed that the amount of PMS was not enough to produce 313 abundant active species in the self-decomposition process. When the catalytic membrane with 4.76%

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LDHs was used, the diameter of the membrane was 50mm and the net weight was 0.05g, it can be 315 seen that the removal rate of AO7 can reach 96.58% within 20min when the catalyst 5mg·L -1 was 316 added, the TOC removal rate can reach 54.76% after 30 minutes of degradation, Under the same 317 conditions, the removal rates of AO7, TOC were 98.19%, 50.29% respectively. When LDHs was 318 5.88wt%, the degradation rate increased from 0.034min -1 to 0.3685min -1 , indicating that the Co-Ni   can inhibit the static interaction between LDHs and AO7 or PMS, which was not conducive to the 343 oxidation reaction. Under acidic condition, the reaction is as follows:

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The main reason was that HA consumed the free radicals in the reaction system, thus inhibiting the 362 degradation rate of AO7. The NOM content of conventional water was usually below 20mg·L -1 with 363 the extension of reaction time. AO7 can still be completely degraded within 20min, which showed 364 the excellent treatment effect of Co-Ni LDHs/PMS system.   T=10℃  T=20℃  T=25℃  T=30℃  T=40℃   T=10℃  T=20℃  T=25℃  T=30℃  T=40℃ C/C0 that may be generated in the catalytic degradation process. In the catalytic membrane/PMS system, 398 it generally generated SO 4 ·-, ·OH , 1 O2 and O 2 ·-. As can be seen from Fig.11 results showed that the production of PMS mainly occurs on the surface of the catalyst, and the 407 activation of PMS produces SO 4 ·-, ·OH ; When 30mmol·L -1 furfuryl alcohol was added to the reaction system, the removal rate of AO7 decreased to 25.92% after 20min, the catalytic degradation 409 was greatly inhibited; When 100mmol·L -1 p-benzoquinone was added, we found that the 410 degradation rate of AO7 by LDHs was 2.22% within 20min, which showed that there was O 2 ·in 411 the degradation process.

Analysis of reaction mechanism 422
Firstly, AO7 was adsorbed on the surface of the catalytic membrane with large specific surface 423 area and strong adsorption capacity. The catalytic mechanism of LDHs/PES catalytic membrane 424 was revealed by comparing the surface element valence of the catalyst before and after the reaction.

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In general, the peaks of Ni2p3/2 and Ni2p1/2 correspond to 854.23eV and 860.78eV, the spin indicated that the Co(Ⅲ)/Co(Ⅱ) and Ni(Ⅲ)/Co(Ⅱ) cycles were involved in the activation of PMS 438 by LDHs. The reduction of Co(Ⅱ) was attributed to the reduction of Co(Ⅱ) to Co(Ⅲ), which led to the oxidation cycle of Co 2+ -Co 3+ -Co 2+ .

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The reaction mechanism was as follows (Fig.13  According to the Table 5 and Figure.14a, Co-Ni LDHs degrades AO7 at a higher rate than Co-   487 Availability of data and materials The datasets used and/or analyzed during the current study 513 are available from the corresponding author on reasonable request.