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. 2022 Jun 11;12(1):9676.
doi: 10.1038/s41598-022-13664-6.

Highly efficient engineered waste eggshell-fly ash for cadmium removal from aqueous solution

Adina-Elena Segneanu  1 , Catalin Nicolae Marin  2 , Gabriela Vlase  3 , Claudiu Cepan  4 , Maria Mihailescu  4 , Cornelia Muntean  4 , Ioan Grozescu  4
Affiliations

Highly efficient engineered waste eggshell-fly ash for cadmium removal from aqueous solution

Adina-Elena Segneanu et al. Sci Rep. .

Abstract

Sustainable waste and water management are key components of the newest EU policy regarding the circular economy. Simple, performant and inexpensive water treatment methods based on reusing waste are prerequisites for human health, sustainable development and environmental remediation. The design of performant, cost-effective absorbents represents a topical issue in wastewater treatment. This study aimed to investigate the development of a newly engineered adsorbent by functionalizing two different types of waste (industrial and food) with magnetic nanoparticles as environmentally friendly, highly efficient, cheap material for cadmium removal from aqueous solutions. This nano-engineered adsorbent (EFM) derived from waste eggshell and fly ash was used to remove the cadmium from the aqueous solution. SEM analysis has demonstrated that magnetite nanoparticles were successfully loaded with each waste. In addition, was obtained a double functionalization of the eggshell particles with ash and magnetite particles. As a result of this, the EFM surface area substantially increased, as confirmed by BET. A comprehensive characterization (BET, FT-IR, SEM, XRD and TGA) was performed to study the properties of this newly engineered adsorbent. Batch experiments were conducted to investigate the influence of different reaction parameters: temperature, pH, contact time, dosage adsorbent, initial concentration. Results showed that cadmium adsorption reached equilibrium in 120 min., at pH 6.5, for 0.25 g of adsorbent. The maximum efficiency was 99.9%. The adsorption isotherms research displayed that the Cd2+ adsorption fitted on the Freundlich model indicated a multi-molecular layer adsorption process. In addition, the thermodynamic study (ΔG < 0, ΔH > 0; ΔS > 0) shows that cadmium adsorption is a spontaneous and endothermic process. The adsorbent kinetic study was described with the pseudo-second-order model indicating a chemisorption mechanism. Desorption results showed that the nano-engineered adsorbent (EFM) can be reused. These data confirmed the possibility to enrich relevant theoretical knowledge in the field of waste recovery for obtaining newly designed adsorbents, performant and inexpensive for wastewater remediation.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
The nitrogen adsorption–desorption isotherms for EFM adsorbent.
Figure 2
Figure 2
XRD spectra of magnetite.
Figure 3
Figure 3
XRD spectra of eggshell.
Figure 4
Figure 4
XRD spectra of fly ash sample.
Figure 5
Figure 5
(a) XRD spectra of M1. (b) XRD spectra of M2. (c) XRD spectra of magnetite, eggshell, fly ash, M1 and M2.
Figure 6
Figure 6
Two-dimensional image of the magnetite particle obtained by the SEM technique.
Figure 7
Figure 7
Two-dimensional image of the ash fly particle obtained by the SEM technique.
Figure 8
Figure 8
EDS spectra of fly ash sample.
Figure 9
Figure 9
(a) Two-dimensional image of the eggshell particle obtained by the SEM technique. (b) Two-dimensional image of the eggshell particle obtained by the SEM technique.
Figure 10
Figure 10
(a) Two-dimensional image of M1 particle obtained by the SEM technique (magnitude 3 µm). (b) Two-dimensional image of M1 particle obtained by the SEM technique (magnitude 5 µm).
Figure 11
Figure 11
SEM M1- Live map.
Figure 12
Figure 12
(a) Two-dimensional image of M2 particle obtained by the SEM technique (magnitude 3 µm). (b) Two-dimensional image of M2 particle obtained by the SEM technique (magnitude 5 µm).
Figure 13
Figure 13
M2 SEM—Live map.
Figure 14
Figure 14
(a) Two-dimensional image of M1 particle obtained by the SEM technique (magnitude 30 µm). (b) Two-dimensional image of M2 particle obtained by the SEM technique (magnitude 50 µm).
Figure 15
Figure 15
IR spectra for adsorbent raw material samples (magnetite, eggshell and fly ash).
Figure 16
Figure 16
FT-IR spectra of adsorbent (both molar ratios: M1 and M2) and its raw materials.
Figure 17
Figure 17
(a) Thermogravimetric analysis of the fly ash sample in the range of 30–500 °C with a heating rate of 10 °C/min in open aluminum crucibles in the air atmosphere. (b) Thermogravimetric analysis of the eggshell with a heating rate of 10 °C/min up to 500 °C.
Figure 18
Figure 18
Thermogravimetric analysis for eggshell: fly ash binary mixture in a 1: 3 mass ratios obtained in the range of 30–500 °C.
Figure 19
Figure 19
Thermogravimetric analysis for eggshell: fly ash binary mixture in a 3:1 mass ratio obtained in the range of 30–500 °C.
Figure 20
Figure 20
The hysteresis loop of sample M2.
Figure 21
Figure 21
The hysteresis loop of sample M1.
Figure 22
Figure 22
The hysteresis loop of magnetite.
Figure 23
Figure 23
Frequency dependence of the magnetite, M1, M2 of the complex magnetic permeability.
Figure 24
Figure 24
(a) The relationship between different material dosage and the cadmium removal efficiency. (b) The relationship between different material dosage and the cadmium adsorption capacity.
Figure 25
Figure 25
(a) Relationship between initial concentration and removal efficiency (%). (b) Relationship between initial concentration and adsorption capacity (mg/g).
Figure 26
Figure 26
(a) Effect of pH variation on cadmium removal efficiency. (b) Effect of pH variation on adsorption capacity.
Figure 27
Figure 27
(a) Effect pf contact time on cadmium adsorption capacity (mg/g). (b) Effect of contact time on cadmium removal efficiency (%).
Figure 28
Figure 28
(a) Relationship between temperature and heavy metal removal efficiency. (b) Relationship between temperature and heavy metal adsorption capacity.
Figure 29
Figure 29
Relationship between adsorbents removal efficiency and contact time.
Figure 30
Figure 30
(a) Pseudo first-order model fitting diagram. (b) Pseudo second-order model fitting diagram. (c) Intraparticle diffusion model fitting diagram.
Figure 31
Figure 31
(a) FT-IR spectra of adsorbent (both molar ratios: M1 and M2) prior adsorption. (b) FT-IR spectra of adsorbent (both molar ratios: M1 and M2) after cadmium adsorption.
Figure 32
Figure 32
(a) Two-dimensional image of M1 particle obtained by the SEM technique (magnitude 10 µm) before adsorption. (b) Two-dimensional image of M1 particle obtained by the SEM technique (magnitude 10 µm) after adsorption.
Figure 33
Figure 33
(a) Two-dimensional image of M2 particle obtained by the SEM technique (magnitude 5 µm) before adsorption. (b) Two-dimensional image of M2 particle obtained by the SEM technique (magnitude 5 µm) after adsorption.
Figure 34
Figure 34
(a) EDX spectra of M1prior adsorption. (b) EDX spectra of M2 prior adsorption.
Figure 35
Figure 35
(a) EDX spectra of M1 after adsorption. (b) EDX spectra of M2 after adsorption.
Figure 36
Figure 36
(a) The relationship between the desorption rate and time. (b) Reuse of EFM.
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