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Open Access Research Article

Comparative Study on Cu(II) and Pb(II) Removal from Water Using MnFe2O4 and MnFe2O4/Zeolite Hybrid Adsorbents

1 * , 1 , 1 , 1,2,3 , 1 , 1 , 3

Received Apr 2, 2026 |Revised May 26, 2026 |Accepted Jun 8, 2026

Copyright © 2026 The Authors. This publication is licensed under CC BY 4.0 .
Published Jul 7, 2026 | DOI: https://doi.org/10.62755/gsm.2026.07
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Abstract

MnFe2O4 and MnFe2O4-Zeolite have been synthesized from sand and zeolite using the co-precipitation method for absorbing ions Pb(II) and Cu(II) in aqueous media. Samples were then characterized using SEM-EDX, XRD, VSM, BET, and AAS. The results of SEM-EDX show that the particle shape of MnFe2O4 and MnFe2O4-Zeolite is not uniform. MnFe2O4 particle size is 5-25 μm, and MnFe2O4-zeolite 2-29 μm, and there are impurities such as Mg, Cl, Ti, and V. XRD results confirm the presence of MnFe2O4 and other phases such as TiO2 and SiO2. VSM measurement shows that both MnFe2O4 and MnFe2O4-Zeolite are soft magnets with coercivity values of 302.12 and 406.04 Oe respectively. While BET analysis shows that the surface area, pore volume, and pore size of MnFe2O4-zeolite are 222.91 m2/g, 0.30 cm3/g, and 2.70 nm, respectively, larger than those of MnFe2O4. Then, the AAS measurement shows the optimum adsorption for Pb and Cu ions using MnFe2O4 at a dose of 100 mg/L are 96.59% and 99.24%, while for the MnFe2O4–zeolite adsorbent for Pb ion at a dose of 100 mg/L is 96.91% and for Cu ion at a dose of 50 mg/L is 99.54%. In general, it was found that the adsorption percentage for both Pb and Cu ions was higher using the MnFe2O4–zeolite than the MnFe2O4.

Keywords:
Co-Precipitation MnFe2O4-Zeolite Adsorbents Pb(II) Removal Cu(II) Removal Heavy Metal Adsorption

1. INTRODUCTION

Lead (Pb) and copper (Cu) are known as toxic heavy metals that pose serious risks to human health. Even at low concentrations, lead exposure can damage vital organs such as the kidneys, liver, and reproductive system, while excessive copper intake may cause gastrointestinal disorders and, in severe cases, death [1,2,3,4,5]. Given the negative impact caused by waste metal ions Pb and Cu, it is important to purify water to remove contaminants from Pb and Cu ions [6]. Various conventional techniques can be carried out, such as reverse osmosis [7], ion exchange [8], chemical precipitation [9], solvent extraction [10], etc. The adsorption method is the most appropriate method for removing heavy metal ions from water, with high effectiveness and economy [11].

Several adsorbents have been used to adsorb heavy metal ions from aqueous solutions; namely, sawdust of eucalyptus, dates, and limes [12], α−Fe3O4 nanoparticles [13,14,15], membrane [16], carbon [17], bentonite [18], zeolite [19][20], manganese ferrite [21], zinc ferrite [22], manganese ferrite-biochar [23] and bentonite-manganese ferrite [24]. Some of these adsorbents have disadvantages such as low adsorption and difficulty in separating from the solution [25]. With the development of research on advanced materials on water pollution by heavy metals, research on manganese ferrite (MnFe2O4) adsorbents continues to grow every year. MnFe2O4 adsorbent can be used to remove heavy metal ions with magnetic separation from the solution [26]. However, the MnFe2O4 adsorbent is easily agglomerated in the liquid phase, reducing the surface area and lowering the adsorption capacity. Zeolite has a larger surface area, more active sites, and high porosity, which can increase the adsorption efficiency [27]. Thus, this study reports the synthesis of MnFe2O4 and MnFe2O4–zeolite from natural iron sand using the co-precipitation method [28,29,30,31], along with the evaluation of their ability to adsorb Pb(II) and Cu(II) ions from aqueous solution.

2. EXPERIMENTAL SECTION

2.1 Materials

The materials used in this study were 200 mesh natural iron sand, 32% HCl (Merck), 25% NH4OH (Technical), MnCl2 98% (Merck), Zeolite Clinoptilolite from PT. Sari Mas in Medan (Indonesia), Ethanol 96% (Technical), and NaOH 98% (Technical).

2.2 Methods

In this study, the synthesis of MnFe2O4 and MnFe2O4–zeolite has been done using the co-precipitation method. The co-precipitation method has a simple process and can produce particles that are very small grain size and tend to be more uniform. However, the coprecipitation method will not be able to remove impurities completely. MnCl2, iron sand, and clinoptilolite zeolite were used as the main precursors. Iron sand that has passed 200 mesh is dissolved using 17 ml of HCl and stirred at 500 rpm for 30 minutes at 80 oC, then filtered using Whatman filter paper (Grade 40 Circles). The iron sand filtrate was then mixed with MnCl2 solution at a ratio of 2:1 volume. Furthermore, stirring was carried out with a magnetic bar at 500 rpm at room temperature until the solution became homogeneous. MnFe2O4–zeolite was made by adding 1 gram of zeolite to the solution, followed by stirring for 40 minutes at 500 rpm at room temperature. Next, the temperature of the solution was changed to 70°C before adding sodium hydroxide solution (5 mol/L) to adjust the solution pH value to 11, after which the resulting solution was stirred for 1 hour. The precipitated composite was then dried in an oven at 100°C for 24 hours. The composite was then crushed using a mortar and was ready to be used as an adsorbent. Next, prepare the following parameters (pH = 5, T = 25 oC, t = 60 minutes, Ci = 8 mg/L) in the form of a solution and put the absorbent into the next batch absorption test.

2.3 Characterization

The samples were then characterized using X-ray diffraction (XRD, SmartLab Rigaku) and Scanning Electron Microscopes (SEM-EDX, Hitachi SU-3500), Brunauer Emmett-Teller (BET, Micrometrics ASAP 2020, USA), and room temperature hysteresis loop measured by Vibrating Sample Magnetometer (VSM 250). In the batch adsorption process using a shaker carried out at optimum conditions (pH=5, T = 25 oC, t = 60 minutes, Ci= 8 mg/L)[24], [32] and the results will be tested using Atomic Absorption Spectrometry (AAS Agilent Technologies-200 series AAA/240 FS AA).

3. RESULT AND DISCUSSION

3.1 Adsorbent Characterization

The surface morphology of MnFe2O4 and MnFe2O4–zeolite adsorbents obtained from SEM-EDX measurements are shown in Figure 1. Figure 1a shows that the shape of the MnFe2O4 particles is not uniform, the surface is still not uniform. The non-uniformity of the particle shape is indicated by the size range of the MnFe2O4 adsorbent particles from 3 μm to 25 μm. Particles with a large size (21 μm) experience agglomeration, because natural interactions occur between magnetic particles, causing several agglomerated areas [33]. Figure 1b shows the MnFe2O4–zeolite adsorbent also having a non-uniform particle shape and size. The particle size range of the MnFe2O4–zeolite adsorbents is 2 μm to 29 μm. It seems that, on average, the particle size of MnFe2O4-zeolite is larger than that of MnFe2O4. Meanwhile, in Figure 1c is the morphology of zeolite with a magnification of 1000, we can see that zeolite is agglomerated. The zeolite exhibits an irregular surface morphology with no distinct surface pores, which can be attributed to the coverage of pores by adsorbed organic impurities, surface oxides, and water molecules trapped within the zeolite structure.

Figure 1. Surface morphology of adsorbents a) MnFe2O4, and b) MnFe2O4–zeolite, c) Zeolite.
Figure 2. Elemental content of adsorbents a) MnFe2O4, and b) MnFe2O4–Zeolite, c) Zeolite.

The elemental content of MnFe2O4 and MnFe2O4–zeolite adsorbents that are also obtained from SEM-EDX measurements is shown in Figure 2. Figure 2a shows that the MnFe2O4 adsorbent has several elements such as O, Na, Mg, Al (0.72%), Si (0.28%), Cl, Ti, V, Mn, and Fe. All these elements are mostly found in all iron sands with different percentages. The highest percentage of elemental content was in the elements O, Fe, and Mn which are 38.13%, 27.71%, and 8.48%, respectively which confirmed the formation of the MnFe2O4 compound. Whereas Figure 2b shows that the content of Fe (24.77%) and Mn (7.59%) elements decreased, but the content of Al (1.16%) and Si (2.98%) increased. This is due to the presence of Al and Si content in the zeolite. Other elements present in the MnFe2O4–zeolite adsorbent are Na, Mg, Cl, K, Ca, Ti, and V. The elements Na, K, and Ca are cations from zeolite, while the presence of elements Mg, and Ti are predicted to appear from the sand that was used, while Cl probably appears from the use of the HCl solvent during the synthesis process. Element V is thought to have originated from the iron sand milling process which experienced abrasion in the jar mill or ball mill.

Figure 3. The pattern of diffraction peaks in MnFe2O4 and MnFe2O4–zeolite samples.

Figure 3 shows the XRD spectra for MnFe2O4 and MnFe2O4–zeolite. It can be seen that MnFe2O4 adsorbent has several diffraction peaks with different intensities. The highest diffraction peak and several other peaks were identified as phases at values 2θ = 35.57°, 46.82°, 56.76°, and 62.13° with hkl planes (311), (331), (511), and (440) which were matched with JCPDS data No. 73-1964 [34]. At 2θ values of 27.40° and 39.80° TiO2 compounds were identified, while at 2θ values of 12.22° and 16.39° SiO2 compounds were identified. The formation of TiO2 (from iron sand) and SiO2 (from zeolite) can be seen from the presence of Ti, Si, and O elements in the sample as shown in the EDX analysis. Furthermore, in the XRD diffraction pattern of the MnFe2O4–zeolite adsorbent, several peaks were also observed at 2θ values, they are at 12.74°, 16.37°, 20.86°, 26.57°, 35.61°, 39,46°,47, 00°, 56.88°, and 62.00°. In the analysis results, new phases appear at values of 2θ 12.74°, 16.37°, 20.86°, and 26.57°, which were analyzed zeolite compounds (Hydrous sodium aluminum silicate) that were matched with JCPDS data No. 00-019-1180 [35]. Analcime zeolite has the smallest pores and exhibits a compact structure. Compared to other zeolites with ideal unit cells Na16[(AlO2)16(SiO2)32].16H2O [36].

Figure 4. Hysteresis curves of adsorbents for MnFe2O4 and MnFe2O4–zeolite.

Furthermore, Figure 4 presents hysteresis curves from VSM measurements for both MnFe2O4 and MnFe2O4–zeolite composites. The loop shapes confirm that both samples are ferrimagnetic and can be classified as soft magnetic materials [37]. The pure MnFe2O4 sample exhibits a saturation magnetization (Ms) of 1.03 emu/g, remanent magnetization (Mr) of 0.05 emu/g, and coercivity (Hc) of 302.12 Oe. In contrast, the MnFe2O4–zeolite composite shows Ms = 1.02 emu/g, Mr = 0.06 emu/g, and Hc = 406.04 Oe. The slight reduction in Ms in the composite is attributed to the dilution by non-magnetic zeolite phases [38]. The low absolute values of Ms, Mr, and Hc for both samples are likely influenced by the presence of gangue or impurity phases, as evidenced by EDX and XRD analyses [39].

Figure 5. Adsorption-desorption isotherms of N2 from adsorbents a) MnFe2O4, and b) MnFe2O4–zeolite.

The adsorption-desorption isotherms of N2 from MnFe2O4 and MnFe2O4–zeolite samples results that are obtained from the BET measurement, are shown in Figure 5. The N2 adsorption-desorption isotherms of the two adsorbents, including the type V isotherm with the H2 hysteresis loop between the adsorption and desorption curves at higher relative pressures, which shows a mesoporous surface with a complex pore structure interconnected with different sizes [40][41]. The mesoporous surface is evidenced by the pore size of the MnFe2O4 and MnFe2O4–zeolite adsorbents, which are 2.63 nm and 2.70 nm. Differences in the shape and size of pores are caused by non-uniform particle size and shape, as shown by the SEM analysis. Calculation of the specific surface area of MnFe2O4–zeolite (222.91 m2/g) is much larger than that of MnFe2O4 (193.03 m2/g). Besides that, the pore volume of MnFe2O4–zeolite (0.30 cm3/g) is larger than that of the MnFe2O4 adsorbent (0.25 cm3/g). This is clearly due to zeolite being a material that has a high specific surface area and high porosity [42].

3.2 Adsorption of Pb and Cu

The Adsorption capacity of Pb and Cu ions by MnFe2O4 and MnFe2O4–zeolite adsorbents is shown in Table 1. The adsorption capacity and removal efficiency are obtained using:

(1)
(2)

with: q = Adsorption capacity (mg/g), Ci = initial concentration (mg/L), Ce = Final concentration (mg/L), V= volume of adsorbate solution (L), W = mass of magnetic powder (g), R = Removal Efficiency (%).

Table 1. The adsorption capacity of Pb and Cu ions by MnFe2O4 and MnFe2O4 – Zeolite adsorbents.
Dose (mg) pH Contact Time (minutes) MnFe2O4 MnFe2O4 – Zeolite
Concentration (mg/L) Adsorption Capacity (mg/g) Concentration (mg/L) Adsorption Capacity (mg/g)
Pb Cu Pb Cu Pb Cu Pb Cu
Ci Ce Ci Ce Ci Ce Ci Ce
50 5 60 8 0.276 8 0.061 2.57 2.44 8 0.248 8 0.037 2.58 2.65
100 5 60 8 0.273 8 0.064 3.86 3.97 8 0.261 8 0.040 3.88 3.98
150 5 60 8 0.282 8 0.069 7.72 7.94 8 0.263 8 0.047 7.74 7.96

As can be seen from Table 1 for MnFe2O4 the optimum adsorption capacity values were obtained at a dose of 50 mg/L for both Pb (7.72 mg/g) and Cu (7.94 mg/g) respectively. For MnFe2O4–zeolite, the optimum adsorption capacity was also observed at a dose of 50 mg/L for Pb (7.74 mg/g) and Cu (7.96 mg/g). The adsorption capacity decreased by increasing the dose in both absorbents. This is predicted due to all the active sites are completely exposed at lower doses, whereas only a small proportion of active sites are exposed at higher doses. Thus, higher adsorbent doses can cause aggregation, which decreases the total surface area of the adsorbent and causes a decrease in adsorption [43]. Another possibility could be caused by the unsaturation of adsorption sites through adsorption reactions [44].

The optimum adsorption capacity value obtained for MnFe2O4–zeolite adsorbent is slightly larger compared to the MnFe2O4 adsorbent for both Pb and Cu. This is due to the addition of zeolite to the adsorbent which increases the surface area, pore volume, and pore size thereby increasing the number of active sites on the surface, which can increase the adsorption capacity [27].

Figure 6. The removal efficiency of Pb(II) and Cu(II) metal ions for MnFe2O4 dan MnFe2O4-Zeolite adsorbents.

The removal efficiency of Pb(II) and Cu(II) metal ions for MnFe2O4 and MnFe2O4-Zeolite adsorbents at pH=5, T=25 °C, t= 60 minutes, Ci= 8mg/L is shown in Figure 6. From Figure 6, It can be seen that the removal efficiency of Cu(II) ions using both MnFe2O4 and MnFe2O4 -Zeolite adsorbents is higher than the removal efficiency of Pb(II) ions. This is due to the smaller radius of Cu(II) ions (0.72 Å) compared to Pb(II) (1.29 Å) so that Cu(II) metal ions can easily occupy the adsorption active sites on the adsorbent surface [31][32]. The removal efficiency value is also increased when the adsorbent dose increases from 50, 100, and 150 mg/L. By increasing the adsorbent dose, the number of active sites is also increased. Then particle aggregation will occur, which makes the adsorption efficiency of Pb and Cu increase.

The removal efficiency is also influenced by the use of adsorbent pH, where if the pH used is more than 6, Pb(II) ions will precipitate in the form of hydroxide Pb(OH)2, which will reduce the concentration of Pb ions in the solution and then decrease the removal efficiency [1]. The presence of hydrogen ions (H+) from the deprotonation of hydroxyl groups in water also affects the removal efficiency, where H+ ions will compete with Pb(II) and Cu(II) ions to occupy active sites on the adsorbent [33].

The removal efficiency of Pb and Cu ions using MnFe2O4-zeolite is higher than MnFe2O4 adsorbent, which is also due to the addition of zeolite increases the surface area, thus increasing the number of adsorption active sites on the adsorbent surface [32], and also with the presence of Na+ cations from zeolite analcime can be exchanged with Pb2+ (1.29A) or Cu2+ (0.72A) cations [34][35]. Where the radius of Na ions is 1.02 Å, the addition of zeolite increases the surface area and increases the number of active adsorption sites on the surface of the adsorbent, thereby increasing the adsorption capacity.

Table 2. The comparison of adsorption capacity with various adsorbents for Pb(II), and Cu(II).
No Sample Adsorption capacities (mg g−1) ref
Pb Cu
1 chitosan/graphene oxide composites 76.9 [45]
2 GO 328 [46]
3 EDTA−GO 479 [46]
4 EDTA−RGO 204 [46]
5 amino-functionalized carbon nanotubes 58.3 [47]
8 Fe3O4/Cu-MOFs 219.00 [49]
9 ZnO/MMT 88.50 54.06 [50]
10 CG 16.95 6.64 [51]
11 CG-0.5GEC 16.95 7.91 [51]
12 CG-1.0GEC 17.01 7.54 [51]
13 CG-2.0GEC 17.70 8.64 [51]
14 CMS@CS 63.7 [52]
15 CMS@CS-F 66.7 [52]
16 PANI@APTS-Fe3O4/ATP-0.7 (288K) 265.25 180.18 [53]
17 PANI@APTS-Fe3O4/ATP-0.7 (298K) 270.27 189.03 [53]
18 PANI@APTS-Fe3O4/ATP-0.7 (308K) 273.22 198.80 [53]
19 EDTA-mGO (298K) 481.2 246.1 [54]
20 EDTA-mGO (308K) 548.1 289.4 [54]
21 EDTA-mGO (318K) 508.4 301.2 [54]
22 chitosan-pyromellitic dianhydride 66.7432 [55]
23 CFZ10-68 109.890 57.803 [56]
24 ZRef – FAU 103.093 57.803 [56]
25 Oxidized MWCNT/SDBS 66.95 [57]
26 Oxidized MWCNT 17.5 [58]
27 Activated carbon/zeolite 549.11 [59]
28 MnFe2O4 7.72 7.94 This work
29 MnFe2O4 – Zeolite 7.74 7.96 This work

In Table 2, the comparison of adsorption capacity with various adsorbents for Pb(II), and Cu(II). As can be seen from Table 2, the adsorption capacity of Pb and Cu by several researchers using different samples. For example, in sample CG, batch mode adsorption studies of Cu(II), Ni(II), Pb(II), and Co(II) were conducted at 25°C using 200 ml of metal ion solutions with concentrations ranging from 10-50 mg/L and 400 mg of adsorbent with an adsorption capacity of 16.95 mg/g for Pb metal and 6.64 mg/g for Cu metal [44]. Compared to the results of our research which was also conducted at 25°C using a 1L water solution has a fairly good adsorption capacity for MnFe2O4 absorbent of 7.72 mg/g for Pb metal and 7.94 mg/g for Cu metal. While MnFe2O4-Zeolite absorbent has an absorption capacity of 7.74 mg/g for Pb metal and 7.96 mg/g for Cu metal. The amount of both absorbents was 150 mg, and the initial concentration of Pb and Cu metal was 8 mg/L as seen in Table 1. We didn’t do the variation concentration in this work due to the limitations of the samples of Pb and Cu Metals.

4. CONCLUSION

In this study, MnFe2O4 and MnFe2O4–zeolite were successfully synthesized from sand and zeolite using the Co-precipitation method for use as adsorbents for the adsorption of Pb(II) and Cu(II) ions from aqueous media. The results of the SEM-EDX analysis showed that the MnFe2O4 and MnFe2O4–zeolite particles had non-uniform particle sizes with some impurities present. XRD analysis confirmed the presence of impurities with the appearance of TiO2 and SiO2 peaks. Both adsorbents are ferrimagnetic and show soft magnet behavior, with the coercivity value of MnFe2O4–zeolite being larger than that of MnFe2O4. The BET analysis also showed that the surface area, pore volume, and pore size of the MnFe2O4-zeolite adsorbent are larger than those of the MnFe2O4 adsorbents. From the adsorption test with the influence of the adsorbent dose, there was an increase in the percentage of optimum adsorption on Pb and Cu by using the MnFe2O4-zeolite adsorbent. From this study, it was found that MnFe2O4-zeolite is a very effective sorbent in removing Cu and Pb ions from aqueous solution. This is because it has a good absorption capacity, which is above (>95%) for each heavy metal, and increased absorption after compositing with zeolite.

Acknowledgments

The research/publication of this article was a collaboration between the National Research and Innovation Agency (BRIN) and Universitas Sriwijaya, and part is funded by DIPA of Public Service Agency of Universitas Sriwijaya 2023. Nomor SP DIPA-023.17.2.677515/2023, On November 30, 2022. By the Rector’s Decree Number: 0188/UN9.3.1/SK/2023, On April 18, 2023.

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