Removal of cd(ii) from water by using graphene oxide–mnfe2o4 magnetic nanohybrids - Nguyen Huu Hieu

Journal of Science and Technology 55 (1B) (2017) 109–121 REMOVAL OF Cd(II) FROM WATER BY USING GRAPHENE OXIDE–MnFe2O4 MAGNETIC NANOHYBRIDS Nguyen Huu Hieu1, 2, *, Tran Ba Kiet1, Nguyen Hoan Kiem1, Nguyen Thi My Huyen2 1Faculty of Chemical Engineering, HCMUT–VNUHCM 268 Ly Thuong Kiet Street, Ward 14, District 10, Ho Chi Minh City, Vietnam 2Key Laboratory of Chemical Engineering and Petroleum Processing, HCMUT–VNUHCM 268 Ly Thuong Kiet Street, Ward 14, District 10, Ho Chi Minh City, Vietnam *Email: nhhieubk@hcmut.edu.vn Received: 30 December 2016; Accepted for publication: 3 March 2017 ABSTRACT In this work, graphene oxide–manganese ferrite (GO–MnFe2O4) magnetic nanohybrids were synthesized by co–precipitation technique. The adsorption properties of GO–MnFe2O4 for efficient removal of Cd(II) from contaminated water were investigated. The nanohybrids were characterized by using X–ray diffraction, Fourier transform infrared spectroscopy, Brunauer– Emmett–Teller specific surface area (BET), transmission electron microscopy, and vibrating sample magnetometry (VSM). VSM result showed the high saturation magnetization values Ms = 27.1 emu/g, the BET specific surface area was 84.236 m2/g. Adsorption experiments were carried out to evaluate the adsorption capacity of the GO–MnFe2O4 magnetic nanohybrids and compared with MnFe2O4 nanoparticles and GO nanosheets. The equilibrium time for adsorption of Cd(II) onto the nanohybrids was 240 minutes. Experimental adsorption data were well–fitted to the Langmuir isotherm and the pseudo–second–order kinetic equation. The experimental results showed that adsorption of Cd(II) using GO–MnFe2O4 magnetic nanohybrids was better than MnFe2O4 and GO with a maximum adsorption capacity of 121.951 mg/g at pH 8. Reusability, ease of magnetic separation, high removal capacity, and fast kinetics lead the GO– MnFe2O4 nanohybrids to be promising adsorbents for removal heavy metals from contaminated water. Keywords: cadmium removal, adsorption, magnetic nanohybrids, graphene oxide, manganese ferrite. 1. INTRODUCTION The strong development of industrialization and urbanization has made emissions into the environment large amounts of heavy metals. Thus, using contaminated water can have serious health effects. Among all heavy metals such as As, Pb, Ni, Cu, Hg, Cd, cadmium is considered one of the most toxic heavy metal with acceptable levels one–tenth those of most of the other toxic metals [1, 2]. The maximum permissible value for worker according to German law is 15 μg/L. For comparison: Non–smokers show an average cadmium blood concentration of Removal of Cd(II) from water by using graphene oxide–MnFe2O4 magnetic nanohybrids 110 0.5 μg/L [3]. Severe risks of cadmium on human health such as vomiting, diarrhea, shortness of breath, lung edema, destruction of mucous membranes, kidney damage, “itai–itai” disease [4, 5]. Therefore, it is necessary to remove Cd(II) from contaminated water. To remove the heavy metals from contaminated water, many studies show that the magnetic nanohybrids of iron oxide–based materials (Fe3O4) or ferrite materials (MFe2O4, M = Ni, Mn, Zn, Co) were effective adsorbents [6, 7]. One of them, the manganese ferrite MnFe2O4 were used as adsorbent with many advantages such as high magnetic permeability, low magnetic losses, more the active functional groups on the surface [8]. However, magnetic nanohybrids MnFe2O4 showed some disadvantages such as instability and agglomeration. Another adsorbent is graphene oxide (GO) can be used. GO has a large number of oxygenated functionalities and high surface area. Therefore, GO can be a good adsorbent for many ion heavy metals, but after the treatment is still challenging about recovering and agglomeration. To overcome the disadvantages of both GO and magnetic nanohybrids MnFe2O4, GO– MnFe2O4 magnetic nanohybrids adsorbent was synthesized and investigated their usage for removal of Cd(II) from contaminated water. GO–MnFe2O4 synthesized by co–precipitation technique was characterized using X–ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller specific surface area (BET), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Adsorption experiments were carried out to evaluate the adsorption capacity of the GO–MnFe2O4 magnetic nanohybrids and compared with MnFe2O4 nanoparticles and GO nanosheets. 2. MATERIALS AND METHODS 2.1. Materials Graphite (particle size < 20 µm) was purchased from Sigma Aldrich, Germany. Sulfuric acid (98 wt%), hydrogen peroxide (30 wt%), sodium nitrate (99 wt%), malachite green (99 wt%), potassium iodide (99 wt%), ascorbic acid (99 wt%), PVA (molecular weight 80,000, degree > 98 %), ferric chloride hexahydrate (99 wt%), manganese chloride (99 wt%), sodium hydroxide (99 wt%), and cadmium nitrate (99 wt%) were purchased from Xilong Chemical, China. Ethanol (96 vol%) and potassium permanganate (99 wt%) were purchased from ViNa Chemsol, Vietnam. 2.2. Synthesis of graphene oxide GO was synthesized by using modified Hummer’s method [9]. In brief, 2.5 g of graphite powder and 1.25 g of sodium nitrate were mixed together. After that, the mixture was added 150 mL of sulfuric acid under constant stirring and the temperature less than 5 °C. After 15 minutes, 7.5 g of KMnO4 was added gradually to the above solution while keeping the temperature less than 20 °C to prevent overheating and explosion. The mixture was sonicated at 35 °C for 2 h. The second oxidation was carried out by adding slowly 7.5 g of KMnO4, and then the mixture was sonicated at 35 °C for 4 h. The resulting solution was diluted by adding 500 mL of water under vigorous stirring. To ensure the completion of the reaction with KMnO4, 30% H2O2 (10 mL) was added. The resulting mixture was washed with H2O and ethanol respectively, then dried. GO sheets were obtained. Nguyen Huu Hieu, Tran Ba Kiet, Nguyen Hoan Kiem, Nguyen Thi My Huyen 111 2.3. Synthesized of MnFe2O4 nanoparticles The MnFe2O4 nanoparticles were synthesized by a co–precipitation method [10]. Briefly, 2.7 g FeCl3.6H2O and 0.99 g MnCl2.4H2O were dissolved in 500 mL of deionized water. The mixture was stirred in ambient atmosphere for 30 min so that the molar ratio of Mn:Fe in the solution was 1:2. The solution was then constantly stirred and heated to 80 °C. Then, 2 M NaOH solution was slowly added to the mixture to raise pH of the solution to 10.5. The color of the solution changed immediately from orange to dark brown. The reaction was continued for 1 hours. The precipitated particles were collected by a magnet and washed 5 times with deionized water before being dried at 80 °C for 1 h. The MnFe2O4 nanoparticles were obtained. 2.4. Synthesis of GO–MnFe2O4 nanohybrids GO–MnFe2O4 nanohybrids were synthesized by a modified co–precipitation method [11]. Brief, 0.5 g GO was added to 400 mL of water and dispersed by ultrasonication for 30 min. In turn, 2.7 g FeCl3.6H2O and 0.99 g MnCl2.4H2O were added to the colloidal GO solution and stirred for 30 min. The solution was then constantly stirred and heated to 80 °C. Then, 2 M NaOH solution was slowly added to the mixture to raise pH of the solution to 10.5. The reaction was continued for 1 h. The precipitate was collected by a magnet and washed 5 times with deionized water before being dried at 80 °C for 1 h. The GO–MnFe2O4 nanohybrids were obtained. 2.5. Characterization XRD patterns were recorded on an Advanced X8 Bruker machine at wavelength (λ) of 0.154 nm at a step of 0.02° (2ߠ) at room temperature at Institute of Applied Materials Science (IAMS–VAST), Ho Chi Minh city. FTIR spectra were obtained in the wavenumber range from 4000 cm–1 to 500 cm–1 during 64 scans on an Alpha–E spectrometer (Bruker Optik GmbH, Ettlingen, Germany) at Institute of Chemical Technology (ICT–VAST), Ho Chi Minh city. TEM images were taken using a JEM–1400 at accelerating voltage of 100 kV at Institute of Applied Materials Science (IAMS–VAST), Ho Chi Minh city. The specific surface area was measured on an Altamira–AMI 200 machine at The Center for Molecular and Nanoarchitecture (MANAR), Viet Nam National University Ho Chi Minh City (VNUHCM). Magnetization curves of MnFe2O4 nanoparticles and GO–MnFe2O4 nanohybrids were measured by MicroSense Easy VSM version 9.13 L machine at Advanced Institute for Science and Technology (AIST–HUST), Ha Noi. 2.6. Adsorption studies Batch adsorption studies experiments were conducted in 250 mL flasks, each containing 20 mL known concentration of Cd(II) in solution. The amount of GO, MnFe2O4, and GO–MnFe2O4 absorbent materials used for the experiment was fixed at 0.02 g. First, kinetic experiments (time: 0–480 min, pH: 6.5, C0: 250 ppm). Secondly, effects of pH (pH: 2–8, C0: 250 ppm, equilibrated time), the solution pH was adjusted by using 1 M NaOH and 1 M HCl. Thirdly, adsorption isotherm (pH: 8, C0: 10–400 ppm, equilibrated time). Afterward, the adsorbent was magnetically separated from the aqueous solution, and the residual concentrations of metal ions were determined by UV–VIS spectrophotometer (UV–VIS–T70+). The quantity of ions Cd2+ adsorbed per unit mass of used adsorbent at equilibrium time were calculated as follows equation: Removal of Cd(II) from water by using graphene oxide–MnFe2O4 magnetic nanohybrids 112 ࢗࢋ ൌ ሺ࡯࢕ି࡯ࢋሻࢂ࢓ (1) where C0 is the initial concentration (mg/L) of Cd2+, Ce is the concentration (mg/L) of Cd2+ after the adsorption, V volume of solution (mL) and m is the weight of GO–MnFe2O4 (g). The adsorption kinetics of Cd2+ onto the surface of GO–MnFe2O4 nanohybrids was studied by pseudo first order and second order equations. The pseudo first order equation can be described as: ܔܖሺࢗࢋ െ ࢚ࢗሻ ൌ ࢒࢔ࢗࢋ െ ࢑૚࢚ (2) The pseudo second order equaiton can be described as: ࢚࢚ࢗ ൌ ૚ ࢑૛ࢗࢋ૛ ൅ ૚ ࢗࢋ ࢚ (3) where qe and qt are the amounts of Cd2+ adsorbed on the surface of GO–MnFe2O4 nanohybrids at equilibrium and at time t (mg/g), respectively and k1, k2 are the rate constants of the pseudo first order (min–1), second order model for adsorption (g.mg–1.min), respectively [12, 13]. In order to evaluate the adsorption capacity of sorbent, the Langmuir and Freundlich models were used. The Langmuir isotherm model is expressed as follows: ࡯ࢋࢗࢋ ൌ ࡯ࢋࢗ࢓ࢇ࢞ ൅ ૚ ࢗ࢓ࢇ࢞࢑࢒ (4) where qe and qm are the amounts of Cd2+ (mg/g) absorbed on the adsorbent at the equilibrium and maximum adsorption capacity, Ce is the equilibrium concentration of Cd2+ in the aqueous solution (mg/L), and kL is the Langmuir binding constant (1/mg). The Freundlich isotherm model is expressed as follows: ࢒࢔ࢗࢋ ൌ ࢒࢔࢑ࢌ ൅ ૚࢔ ࢒࢔࡯ࢋ (5) where the Ce is the equilibrium concentration of Cd2+(mg/L), qe is the amount of Cd2+ (mg/g) absorbed on the adsorbent at the equilibrium adsorption capacity. The kf is the Freundlich binding constant (1/mg) and 1/n is a constant related to the surface heterogeneity. 3. RESULTS AND DISCUSSION 3.1. Characterization of materials 3.1.1. XRD patterns XRD patterns of GO, MnFe2O4, and GO–MnFe2O4 were analyzed for the confirmation of the crystal structure. Figure 1a shows the XRD pattern of the GO, the characteristic peak of GO at 9.86° correspond to (002) reflection from graphitic planes. Figure 1b shows the XRD pattern of MnFe2O4 and GO–MnFe2O4. The diffraction intensity of characteristic peak of GO disappeared due to the loading of MnFe2O4 nanoparticles on the surface of GO sheets, thus increasing the distance between the layers in framework. Further, the diffraction peaks of the GO–MnFe2O4 nanohybrids at 12.02°, 16.83°, 26.92°, 35.38°, 36.05°, 39.53°, 52.05°, 56.47°, and 61.56° can be assigned to the crystalline planes of (101), (111), (220), (311), (222), (400), (422), (511), and (440) of MnFe2O4. These peaks were in agreement the cubic spinel ferrite structure of MnFe2O4 [14, 15]. Fi 3.1 Ad spe (ep rem an (63 O 3.1 in ind are nan d s con gure 1. XRD .2. FTIR sp FTIR spe sorption pea ctra of pure oxy) and C ained in the d 481.23 cm 3.27 cm–1) a or Mn–O in .3. TEM im The morp Figure 3. Th icates that i as, it is the oparticles. how the im firmed the Nguye patterns of (a ectra ctra of GO, ks appearin GO are at –O (alkoxy FTIR spect –1 were the nd low freq octahedral a Figure 2 ages hology of G e TEM ima t is thin 2–d agglomeratio This image ages of GO– homogenou n Huu Hieu, ) GO sheets a MnFe2O4, a g at 3449, 1 tributed to O ) stretching ra of GO–M characteristi uency bond nd tetrahedr . FTIR spect O, MnFe2O4 ge of GO sh imensional s n of the thi indicates the MnFe2O4 n s distributio Tran Ba Kie nd (b) MnFe2 nd GO–Mn 722.41, 162 H, C=O (c vibrations, nFe2O4 nano c peaks of t (481.23 cm– al sites, resp ra of GO and , and GO–M eets in Figu heets. How n GO sheets agglomerat anohybrids u n of MnFe t, Nguyen H O4 nanopartic Fe2O4 nano 8.32, 1383.4 arbonyl and respectivel hybrids. Th he spinel str 1) are in acc ectively [16] GO–MnFe2O nFe2O4 nan re 3a show ever, on the . Figure 3b ion of the M nder differe 2O4 nanopar oan Kiem, N les and GO–M hybrids are 6, and 1056 carboxylic y [10]. All e additional ucture. The ordance with . 4 nanohybrid ohybrids wer s transparent thin sheets shows a TEM nFe2O4 nan nt magnific ticles on the guyen Thi M nFe2O4 nan showed in F .19 cm–1 in groups), C= these band peaks at 633 high frequen the vibratio s. e observed sheets and still remain image of M oparticles. F ations. Thes surface of y Huyen 113 ohybrids. igure 2. the FTIR C, C–O s almost .27 cm–1 cy bond n of Fe– as shown wrinkles the black nFe2O4 igure 3c, e images the GO Re 11 she ind int Mn Fi 3.1 m2 Ta moval of Cd 4 ets and red ependent M eractions be Fe2O4 nano gure 3. TEM .4. BET spe The BET /g. This resu ble 1. The s (II) from wat uce agglom nFe2O4 nano tween MnF particles obt images of (a) cific areas Table 1. BE Materia MnFe2O4 MnFe2O Rice Straw/ MnO2/Fe3O Fe3O4/G CoFe2O4 NiFe2O4/ specific sur lt in medium pecific surfa er by using g eration both particles ou e2O4 nanop ained is abo GO, (b) MnF T specific sur ls BET /GO 4 Fe3O4 4/GO O /Ge Ge face area of level in co ce area of M raphene ox of MnFe2O tside the GO articles and ut 10–15 nm e2O4, and (c, face area of M specific surf 84.2 37. 54.7 60. 119 126. 57.1 GO–MnFe2O mparison w nFe2O4/GO ide–MnFe2O 4 nanopartic sheets wer GO sheets . d) GO–MnFe nFe2O4/GO a ace area (m2 36 8 6 1 .5 36 1 4 nanohybr ith the other much highe 4 magnetic n les and GO e observed, w . The avera 2O4 under di nd other mat /g) Refere Present [16 [17 [17 [17 [18 [18 ids was obta materials, w r than MnF anohybrids sheets. Th hich indica ge particles fferent magni erials. nce work ] ] ] ] ] ] ined as up t hich were s e2O4 nanopa ere is no tes good size of fications. o 84.236 howed in rticles in com Mn nan 3.1 ma ma nan pro Mn Mn Fe3 Co NiF parison w Fe2O4 nano oparticles w .5. Magneti Figure 4 terial behav gnetization oparticles G cess and re Mate Fe2O4/GO Fe2O4 nanop O4/GO Fe2O4/Ge e2O4/Ge Nguye ith previous particles we as decrease zation by VS shows that ior with sm values (M O–MnFe2O cycled by ap Fig Figure Table 2. rials articles n Huu Hieu, publication re anchored d while the s M the GO–M all coercive s) of GO–M 4 can be ea plying exter ure 4. Magne 5. Images of t The saturatio Sat Tran Ba Kie s [16]. Thi on the surfa pecific surfa nFe2O4 nan force (Hc = nFe2O4 w sily remove nal magneti tic hysteresis he magnetic p n magnetizat uration mag t, Nguyen H s result can ce of GO sh ce area was ohybrids s 0.41 Oe). F as of 27.1 d after the c field (see F loops of GO– roperties of G ion MS (emu/ netization M 27.1 53 32.7 32.79 24.28 oan Kiem, N be explaine eets, the agg increased. amples exhi igure 4 also emu/g. W completion igure 5). MnFe2O4. O–MnFe2O4 g) of material s (emu/g) guyen Thi M d as follow regation of M bited soft shows the s ith this va of the adso . s. Refe Prese [ [ [ [ y Huyen 115 s: when nFe2O4 magnetic aturation lue, the rption of rences nt work 19] 20] 18] 18] Re 11 nan mu sat 3.2 3.2 equ 0.9 nan moval of Cd 6 Table 2 s ocomposite ch lower th uration mag . Adsorptio .1. Effect of As shown ilibrium ad The corre 9995. This ohybrids w (II) from wat hows that t is medium an that of M netization of n Test contact time in Figure 6 sorption tim Figu lation coeff indicates th ell fit with th er by using g he saturation compared to nFe2O4. Thi MnFe2O4/G on adsorpt , most of th e was 240 m re 6. Effect o Figure 7. icient (R2) f at the adso e psedo sec raphene ox magnetiza GO and Ge s is due to th O [21]. ion capacity e Cd2+ rem ins. f contact time Pseudo secon or the psed rption proc ond order m ide–MnFe2O tion, MS (em . Additional e presence and adsorp oval took pl on adsorptio d order kinet o second or ess of Cd2+ odel (see Fig 4 magnetic n u/g), of ob ly, the Ms of of GO which tion kinetics ace within f n capacity. ics. der model h onto surfa ure 7). anohybrids tained MnF the MnFe2O led to the r irst 60 mins ad high val ce of GO–M e2O4/GO 4/GO is educe in and the ue, R2 = nFe2O4 3.2 GO eff cap Mn wh low OH the gro ion op .2. Effect of pH is one –MnFe2O4 ect of pH w acity of GO Fe2O4 have en dispersed pH with a 2+ and –CO surface and ups are ion s was decr timum pH co The mach On the su On the su Nguye pH on adso of the mos process. Pre as examine –MnFe2O4 a lot of –O MnFe2O4 large numb OH2+ . Ther the adsorpt ized to –O– eased. Ther ndition for anisms of ad rface of MnF ۻെ rface of GO ۵۽ ૛۵۽ ۵۽ െ ۱۽ ૛۵ ۵۽ െ n Huu Hieu, rption capac t important cipitation o d from 3 to increased w H groups o nanoparticle er of H+ ion efore, Cd2+ i ion capacity and –COO efore, the a adsorption o sorption we e2O4 nanop ۻെ۽۶ ൅ ૛ۻെ ۽۶ ൅ ۽۶ ൅ ۱܌૛ା [11]: െ ۱۽۽۶ ൅ െ ۱۽۽۶ ൅ ۽۶ ൅ ۱܌૛ା ۵۽ െ ۽۶ ൅ ۽ െ ۽۶ ൅ ۽۶ ൅ ۱܌૛ା Figure 8. Eff Tran Ba Kie ity controlling p f cadmium 8. The resu ith increasi f GO and M s in water s, –OH and ons had to reduced. W –, leading to dsorption c f Cd2+ on th re showed th articles (M i ۱܌૛ା ⇌ ۻ ۱܌૛ା ⇌ ሺۻ ൅ ۶૛۽ ⇌ ۱܌૛ା ⇌ ۵ ۱܌૛ା ⇌ ሺ۵ ൅ ۶૛۽ ⇌ ۱܌૛ା ⇌ ۵ ۱܌૛ା ⇌ ሺ۵ ൅ ۶૛۽ ⇌ ect of pH on t, Nguyen H arameters i starts at pH lts were sho ng pH of s nFe2O4 (M [22]), add to –COOH gro compete wit hen the pH the compe apacity was e surface of e following s Mn or Fe) െ ۽۱܌ା ൅ െ ۽ሻ૛۱܌ ൅ ۻ െ ۽۱܌۽ ۽ െ ۱۽۽۱܌ ۽ െ ۱۽۽ሻ૛ ۵۽ െ ۱۽۽۱ ۽ െ ۽۱܌ା ൅ ۽ െ ۽ሻ૛۱܌ ۵۽ െ ۽۱܌۽ adsorption ca oan Kiem, N n adsorption 8.2 [19]. Th wed in Figu olution. On n–OH and that –COO ups become h H+ ions fo was increase tition betwe enhanced. GO–MnFe2O reactions: [10]: ۶ା ૛۶ା ۶ ൅ ૛۶ା ା ൅ ۶ା ۱܌ ൅ ૛۶ା ܌۽۶ ൅ ૛۶ ۶ା ൅ ૛۶ା ۶ ൅ ૛۶ା pacity. guyen Thi M of Cd on s us, in this re 8, the ad the surface Fe–OH wer H groups o positively c r adsorption d, –OH and en Cd2+ ion Thus, pH 4. ା y Huyen 117 urface of study the sorption of GO– e formed f GO. At harged – sites on –COOH s and H+ 8 is the (6) (7) (8) (9) (10) (11) (12) (13) (14) Re 11 3.2 con inc inc La ad Fre T F moval of Cd 8 .3. Effect of Figure 9 centration o reased and reased and t As shown ngmuir plot sorption of undlich isot able 3. Adso kl (l/mg) 0.0172 igure 10. (a) (II) from wat initial conc indicates f Cd2+. At l at higher c end to reach Figure 9. Ef in Table 3 (R2 = 0.9 Cd2+ on G herm model rption constan Langmu qm (mg/g 121.951 Langmuir iso er by using g entration of the adsorp ow concentr oncentration equilibrium fect of initial and Figure 881) compa O–MnFe2O . ts and correl ir ) R 0.9 therm and (b) raphene ox Cd2+ tion capaci ation (0–15 (> 150 m . concentration 10, the high red to Freu 4 well fit w ation coefficie models 2 881 Freundlich i ide–MnFe2O ty was inc 0 mg/L), the g/L), the a of Cd2+ on a er correlatio ndlich plot ith Langm nt (R2) with L . N 1.689 sotherm of ad 4 magnetic n reased wit adsorption dsorption c dsorption cap n coefficien (R2 = 0.94 uir isotherm angmuir and Freundl kf (mg/g)(L 4.356 sorption of Cd anohybrids h increasin capacity wa apacity was acity. t was obtain 36). There model m Freundlich i ich /mg)1/n 1 2+ on GO–M g initial s rapidly slightly ed from fore, the ore than sotherm R2 0.9436 nFe2O4. ab iso an (12 sur GO pre FT VS spe con she int The maxi out 121,951. Figure 11 therm (R2 = d MnFe2O4 1.951 mg/g face of GO sheets and Table Sil Fig In this wo cipitation m IR spectra i M result sh cific surfac firmed the ets, reducin eractions be Nguye mum adsorp This result indicated th 0.9935 and (107.527 m ). The resul sheets, resu increased ad 4. Maximum Mate MnFe2O Graphen CoFe2O NiFe2O Graph icate MCM–4 SWC SWCNT– ure 11. Langm rk, the GO– ethod. XRD ndicated the owed the h e area of GO homogenou g of agglo tween MnFe n Huu Hieu, tion capacity is compared e adsorption 0.9881, res g/g and 34 ts are explai lting in decr sorption site adsorption ca rials 4/GO e oxide 4/Ge 4/Ge ene 1, mesoporou NT COOH uir isotherm 4. MnFe2O4 ma patterns sh existence o igh saturat –MnFe2O4 s distributio meration bo 2O4 nanopar Tran Ba Kie , qm (mg/g) with some o of Cd2+ on pectively). B .364 mg/g ned, when M eased aggre s. pacity qm (mg qm (m 121. 106 105 74. 188. s 10 24. 55. of adsorption CONCLU gnetic nano owed the cr f oxygen–co ion magneti nanohybrid n of MnFe th of MnF ticles and G t, Nguyen H , of obtained ther materia GO and MnF ut the max , respectivel nFe2O4 nan gation of bo /g) of MnFe2O g/g) 951 .3 .26 62 679 0 07 89 of Cd2+ on (a SIONS hybrids wer ystal structu ntaining fu zation value s was obtain 2O4 nanopar e2O4 nanopa O sheets wer oan Kiem, N MnFe2O4/G ls presented e2O4 also w imum adsorp y) are less oparticles w th of MnFe2 4/GO and ot Referenc Present w [23] [18] [18] [24] [25] [26] [26] ) GO and (b) e successfull re of GO–M nctional grou s MS = 27 ed as 84.23 ticles on the rticles and e very stron guyen Thi M O nanocom in the Table ell fit with L tion capaci than GO–M ere anchore O4 nanopart her materials. es ork MnFe2O4. y synthesize nFe2O4 was ps in this m .1 emu/g. T 6 m2/g. 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