Analytical Instrumentation Techniques of FT-IR, XRD, SEM, and EDX for Adsorption Methods of Ni2+ Ions Onto Low Cost Adsorbent

Introduction

Pollution of heavy metals has attracted global attention due to their toxicity, hard decay and accumulation in organisms. Heavy metals accumulate in the tissues of various living organisms and as a result attach to the food chain, affecting humans, posing a health risk ^1-3. Therefore, the treatment of wastewater polluted by heavy metals is an important environmental concern. Ion exchange, solvent extraction, chemical precipitation, ultra-filtration, reverse osmosis, electro dialysis and adsorption are the traditional methods for removing heavy metal ions from polluted water ^4-6. However, absorption is considered to be one of the most popular methods for removing heavy metals from wastewater due to its low cost, in effect, biodegradability, ease of design and high removal efficiency. There are many absorbent materials available, but activated carbon is used to remove heavy metals by the adsorption method because activated carbon has a numerous pores and a large surface area ^{7, 8}.

The literary study shows that no work has been done on Hygrophila auriculata activated nano carbon (HA-ANC) as an adsorbent, as well as low cost and high abundance. Therefore this study focused on the removal of Ni²⁺ ions from the aqueous solution using the HA-ANC by batch adsorption method.

Materials and Methods

Chemicals

Analytical reagent grade chemicals were used. Stock Ni²⁺ ion solution (1000 ppm) was prepared by dissolving required amount of NiSO₄.6H₂O in 1000 ml of double distilled water. Working standards were prepared by diluting the stock solution of Ni²⁺ ions using double distilled water. The ionic solutions of 0.1M HCl and 0.1MNaOH were made for to alter the solution pH.

Procedure for Adsorbent Preparation and Activation

The Hygrophila auriculata stem waste was obtained from the agricultural sites near at Poompuhar, Mayiladuthurai district, Tamilnadu, India. The stem was cut into small pieces, dried in the absence of sunlight and treated with concentrated H₂SO₄ in W/V ratio. The carbonized material washed away by double distilled water until it becomes neutral one and dried further inside the hot air oven at 110 ^oC for 24 hrs. The carbon was activated by using muffle furnace at 1000 ^oC for 6 hours and the activated carbon (HA-ANC) was powdered well and stored in desiccators in order to perform the experiment ⁹.

Batch Adsorption Method

The batch experiments [10] for Ni²⁺ ions removal was determined under various initial pH like 3, 4, 5, 6, 7, 8 and 9 besides temperature ranges from 30 to 60 ^oC at an initial Ni²⁺ ion solution concentration was varied from 10 to 50 ppm with different adsorbent doses and different time intervals such as 15, 30, 45, and 60 minutes. The effect of initial Ni²⁺ ions concentrations was investigated by using 25 mg biomass, initial pH 6 and volume of Ni²⁺ ion solution 50 mL are constant but varied initial Ni²⁺ concentrations at room temperature (30 ^oC). The Ni²⁺ ion solution samples were collected after 60 min. of shaking then centrifuged at 120 rpm, the filtrate was analyzed. The unadsorbed Ni²⁺ ions were measured by using UV-Visible spectrophotometer. The removal percentage and amount of Ni²⁺ ions adsorption were calculated using equation 1 and equation 2 correspondingly.

Mass Balance Relationship Equation Eq. No.

Where, % R is the percentage of removal, q_e is the amount of adsorbed Ni²⁺ ions per unit quantity of adsorbent at equilibrium time (mg g -1), C₀ and C_e are the initial and actual concentration (ppm) of Ni²⁺ ion solutions at equilibrium time, respectively. The V is the volume of the Ni²⁺ ion solution (L), ‘w’ is the weight of the HA-ANC (g).

Analytical Tools for HA-ANC and Ni²⁺/HA-ANC

The determination of surface area, volume and diameter of pores for HA-ANC, BET-BJH methods were used. The FT-IR spectrum is an important tool to study the changes infrequency due to the interaction between adsorbent and adsorbate. The XRD pattern confirms the nature of the adsorbent as well as adsorption of Ni²⁺ ions onto HA-ANC in order to changes of 2θ values. SEM is a substantial tool to evaluate the morphological features and surface characteristics of the fresh adsorbent and treated adsorbent materials and also EDX study gives details about the element compositions ^{11, 12}.

Results and Discussions

The equilibrium data was calculated with the help of batch methodology it’s incorporated some of the effective parameters such as contact time, solution pH, adsorbent dose, temperature ¹³. The data was given in table 1, the result says that the nature of effectiveness of Hygrophila auriculata activated nano carbon (HA-ANC), which indicates the amount of adsorbed Ni²⁺ ions onto HA-ANC increased with increasing temperature. The removal was high (90.737%) at 60 ^oC it’s also declared the removal of Ni²⁺ ions onto adsorbent favored in elevation of temperature as well as low concentration of Ni²⁺ ion solution by 25 mg of adsorbent.

Table 1: Equilibrium Data for the Adsorption of Ni²⁺ ions onto HA-ANC

C0	Ce (Mg / L)				qe (Mg / L)				Removal %
	30oC	40oC	50oC	60oC	30oC	40oC	50oC	60oC	30oC	40oC	50oC	60oC
10	1.804	1.463	0.976	0.926	16.393	17.075	18.048	18.147	81.963	85.375	90.238	90.737
20	5.363	4.877	4.408	3.414	29.275	30.246	31.184	33.173	73.188	75.614	77.960	82.932
30	11.149	10.630	9.263	8.582	37.702	38.741	41.475	42.836	62.836	64.568	69.125	71.393
40	17.103	15.641	14.837	13.917	45.793	48.718	50.327	52.166	57.241	60.897	62.908	65.208
50	25.350	24.471	23.931	22.510	49.300	51.059	52.139	54.981	49.300	51.059	52.139	54.981

According to the BET-BJH method, the surface area, volume and diameter of pores was obtained as 90.067 m²/g, 0.115 cc/g and 3.520 nm, respectively.

Fourier transform infrared (FT-IR) was used to determine the changes of vibration frequency in the functional groups of the adsorbent due to Ni²⁺ ions adsorption. The FT-IR spectrum within 500–4000 cm^-1 for the HA-ANC before and after the adsorption of Ni²⁺ is shown in order to fig. 1, and fig. 2. The peak point of frequency; 2500 to 4000 cm^-1 indicates the single bonds (C-H, O-H, N-H), 2000 to 2500 cm^-1 indicates the triple bonds (C≡C, C≡N), 1500 to 2000 cm^-1  indicates the double bonds (C=C, C=N, C=O) and 500 to 1500 cm^-1 indicates fingerprint region. The FT-IR spectrum of HA-ANC indicates that there is remarkable change in the  peaks at 2997.49 cm-1, 2888.47 cm-1, 1860.25 cm-1, 1560.72 cm-1, 1184.19 cm-1, 1123.42 cm-1, 1035.85 cm-1, 795.09 cm-1, and 525.96 cm-1 respectively which it can be due to Ni2+ binding with functional groups adsorbent. The formation of new peaks, demolition of old peaks and higher to lower as well as lower to higher shifting of peaks were reason for that HA-ANC adsorbed with Ni²⁺ions ^14-16.

Figure 1: FT-IR for HA-ANC Click here to View figure

Figure 2: FT-IR for Ni2+/HA-ANC Click here to View figure

The result of XRD diffractogram for HA-ANC (fig. 3) revealed that the Hygrophila auriculata activated nano carbon is crystalline in nature and resembles the graphite structure ^17-19. After adsorption of Ni²⁺ ions (fig. 4) the surface of adsorbent was disturbed this one leads to new theta values, HA-ANC given in table 2 and Ni²⁺/HA-ANC given in table 3 respectively.

Figure 3: XRD for HA-ANC Click here to View figure

Figure 4: XRD for Ni2+/ HA-ANC Click here to View figure

Table 2: XRD measurements of HA-ANC

Pos. [°2θ]	Height [cts]	FWHM Left [°2θ]	d-spacing [Å]	Rel. Int. [%]
25.2589	1233.20	8.7438	3.52305	100.00
43.5468	384.92	4.5991	2.07663	31.21

 

Table 3: XRD measurements of Ni²⁺/ HA-ANC

Pos. [°2θ]	Height [cts]	FWHM Left [°2θ]	d-spacing [Å]	Rel. Int. [%]
5.0131	23772.90	0.0520	17.61333	100.00
20.3762	708.42	3.3002	4.35492	2.98
23.8854	1206.41	5.9034	3.72244	5.07
26.5138	209.24	9.0362	3.35909	0.88
42.5192	718.56	0.9656	2.12441	3.02

 

SEM images have been used for morphological study of HA-ANC. The SEM micrographs of HA-ANC before and after adsorption of Ni²⁺ ions are shown in Fig. 5,and Fig.6, respectively. In the SEM image of HA-ANC, the porous structure is obvious, but in the case of the used particles, the pores have been covered by the Ni²⁺ions ^{20, 21}.

Figure 5: SEM image for HA-ANC in different magnifications 10 µm, 1 µm and 300 nm Click here to View figure

Figure 6: SEM image for Ni2+/ HA-ANC in different magnifications 10 µm, 1 µm and 300 nm Click here to View figure

The EDX spectrum ^{22, 23} of HA-ANC before and after adsorption of Ni²⁺ ions were evaluated shown in fig. 7 and fig. 8 respectively. The spectrum clearly indicates the peak of element C, there was significant reduction in the intensity of peak of C in the after adsorption of Ni²⁺ ions comparing with the before adsorption. And also the peak of Ni²⁺ ions was notable on the after adsorption of Ni²⁺ ions onto HA-ANC in addition the elemental compositions statistics were given in Table 4 and Table 5 respectively for before and after adsorption Ni²⁺ ions onto HA-ANC. In addition the atomic percentage of carbon reduced form 99.7% to 88.8% bassed on Table 4 and Table 5, it can be usable as remarkable reduction.

Figure 7: EDX for HA-ANC Click here to View figure

Figure 8: EDX for Ni2+/HA-ANC Click here to View figure

Table 4: EDX of Smart Quant Results for HA-ANC

Element	Weight %	Atomic %	Error %	Kratio
C K	85.6	89.7	4.4	0.5959
O K	11.7	9.2	13.9	0.0133
MgK	0.5	0.2	13.2	0.0029
AlK	0.4	0.2	13.2	0.0026
SiK	0.7	0.3	7.2	0.0056
S K	0.3	0.1	18.3	0.0028
ClK	0.4	0.1	19.9	0.0035
CaK	0.4	0.1	27.7	0.0034

Table 5: EDX of Smart Quant Results for Ni2+/HA-ANC

Element	Weight %	Atomic %	Error %	Kratio
C K	84.8	88.8	4.0	0.6254
O K	13.5	10.6	13.6	0.0158
AlK	0.4	0.2	9.9	0.0031
S K	0.4	0.2	15.4	0.0038
ClK	0.2	0.1	30.2	0.0020
NiK	0.6	0.1	20.0	0.0062

 

Conclusion

The Hygrophila auriculata activated nano carbon (HA-ANC)has been used successfully as an adsorbent for the removal of Ni²⁺ ions. The removal of Ni²⁺ ions was found to be 90.737% with an initial concentration of 10 ppm at pH 6 in 60 minutes. The appearance, disappearance and shifting of peaks in the FT-IR spectrum confirmed the adsorption of Ni²⁺ ions onto HA-ANC as well as XRD analysis also provided reasonable evidence for adsorption to the adsorbent. In addition to supporting, the SEM study gives difference in the surface morphology of the adsorbent before and after the adsorption of Ni²⁺ ions as well as EDX also given elemental composition evident of removal of Ni²⁺ ions onto HA-ANC. Finally, it was concluded that the present adsorbent HA-ANC could be a good alternative adsorbent for the removal of heavy metals from aqueous solutions in a very efficient and economical manner.

Acknowledgement

The authors sincerely thank the Government of Tamil Nadu Adi Dravidar and Tribal Welfare Department for providing the fund from Full Time Ph.D Scholars incentive Scheme.

Conflict of Interest

There is no conflict of interest.

Funding Sources

There is no funding source.

References

1. Mousa WM, Soliman SI, El-Bialy AB, Hanaa A Shier. Journal of Applied Sciences Research, 2013; 9(3):1696-170.
2. Pandharipande SL, Rohit P, Kalnake P. International Journal of Engineering Sciences & Emerging Technologies, 2013; 4(2):83-89.
3. Babel S, Kurniawan TA. Journal of Hazardous Materials, 2003; 97:219-243.
   CrossRef
4. Figoli A, Cassano A, Criscuoli A, Mozumder MSI, Uddin MT, Islam MA, Driolo E. Water Research, 2010; 44:97-104.
   CrossRef
5. Arivoli S, Venkatraman BR, Rajachandrasekar T, Hema M. Research Journal of Chemistry and Environment, 2007; 17:70-78.
6. Arivoli S, Kalpana K, Sudha R, Rajachandrasekar T.  E-Journal of Chemistry, 2007; 4:238-254.
   CrossRef
7. Coogan TP, Latta DM, Snow ET, Costa M, Lawrence A. Critical Reviews in Toxicology, 1989; 19:341-384.
   CrossRef
8. Savolainen H. Reviews on environmental health, 1996; 11:167-173.
   CrossRef
9. Arivoli S,  Hema M, Parthasarathy S, Manju N. Journal of Chemical and Pharmaceutical Research, 2010; 2(5):626-641.
10. Arivoli S, Hema M. International Journal of Physical Sciences, 2007; 2:10-17.
11. Nhamo Chaukura, Edna C. Murimba, Willis Gwenzi, Applied Water Science, 2017; 7:2175–2186
    CrossRef
12. Chantakorn Patawat, Ketsara Silakate, Somchai Chuan-Udom, Nontipa Supanchaiyamat, Andrew J. Hunt, Yuvarat Ngernyen, RSC Advances, 2020; 10:21082–21091.
13. Arivoli S, Viji Jain M, Rajachandrasekar T. Material Science Research India, 2006; 3:241-250.
    CrossRef
14. El-Sadaawy M, Abdelwahab O, Alexandria Engineering Journal, 2014; 53(2):399–408.
    CrossRef
15. Gonzalez JF, Silvia R, Gonzalez G, Carmen M, Nabais JM, Valente, Luis OA. Industrial & Engineering Chemistry Research, 2009; 48:7474-7481.
    CrossRef
16. Muniandy L, Adam F, Mohamed AR, E-P Ng. Microporous and Mesoporous Materials, 2014; 197:316–323.
    CrossRef
17. Pavan Kumar GVSR, Komal Avinash Malla, Bharath Yerra, Srinivasa Rao K, Applied Water Science, 2019; 9(3):44,1-9.
    CrossRef
18. Qu D. Journal of Power Sources, 2002; 109:403-411.
    CrossRef
19. Bratek W, Świa̧ tkowski A, Pakuła M, Biniak S, Bystrzejewski, Szmigielski R, Journal of Analytical and Applied Pyrolysis, 2013; 100:192-198.
    CrossRef
20. El-Araby H.A, Ibrahim AMMA, Mangood AH, Abdel-Rahman AAH, Journal of Geoscience and Environment Protection, 2017; 5:109-152.
    CrossRef
21. Gil R R, Ruiz B, Lozano MS, Fuente E, Journal of Analytical and Applied Pyrolysis, 2014; 110(1): 194–204.
    CrossRef
22. Agegnehu Alemu, Brook Lemma, Nigus Gabbiye, Melisew Tadele Alula, Minyahl Teferi Desta. Heliyon, 2018; 4(e00682):1-22.
    CrossRef
23. Xie Youping, Li Hang, Wang Xiaowei, Ng I-Son, Lu Yinghua, Jing Keju. Journal of the Taiwan Institute of Chemical Engineers, 2014; 45(4):1773–1782.
    CrossRef

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