Abstract

Contamination in drinking water from heavy metals like Pb2+ has severe effects on health. In this study, potato peel (PP) was used as the substrate and magnetic iron nanoparticles (MI) were deposited on PP using a co-precipitated method. Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis confirmed the deposition of MI on PP. The L16 (4^4) method of Taguchi design of experiment (DOE) was used for the optimization of adsorption condition, i.e., at 6 pH, 10 min of contact time, and a dose of 15 g/L can give more than 90% removal efficiency of Pb2+ using PP-MI. Contour maps, Taguchi response analysis, and analysis of variance (ANOVA) suggested that pH has a dominant contribution in the removal of Pb2+. The adsorption process was favorable, spontaneous, and exothermic in nature and was followed by pseudo second order kinetics. A comparison of the sorption capacity of PP-MI for Pb2+ with literature values suggested that PP-MI has good potential for the removal of Pb2+.

INTRODUCTION

The cumulative, non-biodegraded, and persistent nature of heavy metals make them an environmental concern even when present in trace amounts (Gupta & Ali 2004). Exposure to heavy metal like Pb2+, even in trace amounts, can cause adverse health effects (Gupta & Ali 2004). Many industries discharge industrial effluents containing Pb2+, which can pose a risk to humans. Therefore, the treatment of Pb2+ prior to discharge is important, but the complex composition of effluents makes treatment difficult (Gupta & Ali 2004). Furthermore, the presence of dissolved organic compounds plays a key role in controlling the physiochemical properties of Pb2+ ions which further enhance the difficulty level for Pb2+ treatment (Gupta & Ali 2004). Out of many treatment methods, adsorption is considered as economic, efficient, and effective for the treatment of heavy metals (Günay et al. 2007; Feng et al. 2010; Dawodu et al. 2012). In the last decade, researchers have improved the quality and cost-effectiveness of adsorbent in the form of zeolites (Panuccio et al. 2009), clay minerals (Hizal & Apak 2006; Dawodu et al. 2012), and organic waste (Mackay et al. 1997). Although these adsorbent techniques are good, because of less surface area, expense, and generation of secondary waste, researchers are now using nano adsorbents (Chang & Chen 2005; Banerjee & Chen 2007; Badruddoza et al. 2011), nano alumina (Mahdavi et al. 2013), functionalized carbon nanotubes (Abbas et al. 2016), and hydroxyapatite nanoparticles (Mohammed et al. 2018). The high absorption abilities of nanoparticles are further enhanced by the use of magnetic nanoparticles which increases the efficiency of solid–liquid separation problems (Plohl et al. 2019). These magnetic particles not only have a large surface area which increases the removal efficiency (%RE) but they are also easily prepared and can be separated from samples to reduce secondary solid waste generation (Plohl et al. 2019). Several attempts have been made to use various forms of nanoparticles, e.g., maghemite nanoparticles (Oukebdane et al. 2018), iron-humic acid, nanopolymers (Rao et al. 2019), etc. In this study, potato peel (PP) (agricultural waste) was used as substrate. Potato is abundantly used as potato chips. Based on the peeling method, 15–40% (% wt) of potato is wasted as potato peel. This potato peel is a major contributor of solid organic waste in food industries (Gebrechristos & Chen 2018). Using potato peel as a substrate will help in reducing solid waste. Magnetic iron (MI) particles were synthesized and coated on PP using the co-precipitated method. The PP-MI was also characterized using FTIR and XRD. The prepared PP-MI is then used as adsorbent material for optimization and isotherm studies for the removal of Pb2+ from drinking water.

MATERIAL AND METHODS

The chemicals used during experiments were FeCl3.6H2O, FeSO4.7H2O, ammonia solution, H2SO4, and Pb(NO3)2,were of analytical grade and purchased from Merck, Pakistan. The potato was purchased from the local market and its peel was used for experimentation. All glassware was Pyrex and washed with 2% HNO3 and double rinsed with deionized water before being used in experimentation. The analysis of Pb2+ was performed on an Atomic Absorption Spectrometer (AAS) (Analyst 800, Perkin Elmer) (American Public Health Association 2005) in triplicate after performing the limit of detection (LOD) and quality checks (QC) test. Samples were also analyzed from the chemistry department, UET and Institute of Chemistry Punjab University (PU) to minimize errors. Characterization of PP-MI was performed using FTIR and XRD from the physics department, UET Lahore.

Preparation of the adsorbent

Potato peel (PP) was dried in sunlight for 8 hr daily for 6 days. The average temperature was 37–41 °C during the drying period. After drying, PP was transferred to an oven at 45 °C. The dried PP was then cut into small pieces, ground into powder form and stored in airtight jars to prevent damp. The mesh size of powdered PP was 60–200 micron. Powdered PP (1 g) was added into 200 mL of distilled water and heated at 80 °C. After that, 10 mL of NH4OH was added to maintain a pH of 10. Ferrous sulfate hepta-hydrate (4.2 g) and ferric chloride hexa-hydrate (6.1 g) were mixed in 100 mL de-ionized water, separately. These salts were then slowly mixed with PP solution at 80 °C. After the complete addition of two iron salts, the combined solution was further heated for 30 min at 80 °C. The solution was cooled down and PP-MI nanoparticles were separated from the solution using a magnetic bar. PP-MI was dried and stored in airtight jars. Characterization of PP-MI was performed using FTIR (JASCO, FT/IR-4100 type A) and XRD (Shimadzu, XRD-7000). The composition of PP was determined in terms of carbohydrates (Dubois et al. 1956), proteins (Rice et al. 2017), fats (Soxhlet apparatus), ash, and metals (Rice et al. 2017).

Taguchi method for design of experiments (DOE)

Design of experiments (DOE) for the Taguchi method is used for the optimization of conditions. Four parameters, i.e., pH (2–8), dose of adsorbent (PP-MI) (5–20 g/L), contact time of adsorption (10–40 min) and initial concentration of Pb2+ (70–90 ppm) was selected. The method L16 (4^4) was selected for Taguchi DOE. It has four parameters and four levels. Table 1 contains the various inputs (16) for the optimization of adsorption conditions. Known solutions of various Pb2+ concentrations (10–90 ppm) were prepared using the standard solutions provided by Perkin Elmer, US (Oukebdane et al. 2018). Analysis of iron which may be leached out during the adsorption process was also carried out using an atomic absorption spectrometer.

Table 1

Composition of potato peel in terms of organic and inorganic content

ParameterMass %Method
Moisture 83.29 ASTM D2216 
Dry mass 16.71 ASTM D2216 
Carbohydrates 10.66 ASTM D5896 
Proteins (Ntot1.38 ASTM D5712 
Fats 0.43 ASTM D5555 
Ash content 1.1 ASTM D5347 
Calcium 0.75 *3,500 B Ca2+ 
Magnesium 0.21 *3,500 B Mg2+ 
Zinc 0.002 *3,500 B Zn2+ 
ParameterMass %Method
Moisture 83.29 ASTM D2216 
Dry mass 16.71 ASTM D2216 
Carbohydrates 10.66 ASTM D5896 
Proteins (Ntot1.38 ASTM D5712 
Fats 0.43 ASTM D5555 
Ash content 1.1 ASTM D5347 
Calcium 0.75 *3,500 B Ca2+ 
Magnesium 0.21 *3,500 B Mg2+ 
Zinc 0.002 *3,500 B Zn2+ 

*Standard methods for the examination of water and wastewater, 20th edition.

RESULTS AND DISCUSSION

Characterization of PP-MI

Chemical analysis of PP was performed to measure moisture content, carbohydrates, proteins, fats, ash, and heavy metals. The results of the composition are given in Table 1. FTIR analysis of PP and PP-MI indicated the binding of iron magnetic particles on PP. The infrared spectra of PP and PP-MI are given in Figure 1. Both PP and PP-MI showed almost the same FTIR spectra except the broad OH peak of PP at 3,434.76 cm−1 (OH stretch) and a new peak of PP-MI at 575.15 cm−1 (Fe–O). This suggests that the interaction of the hydroxyl groups and metal-oxide was generated during the PP-MI synthesis. The characteristic peaks of XRD (Figure 2) at 6.17°, 44.46°, and 51.46° further supported the deposition of MI on PP. These peaks were characteristic peaks of iron nanoparticles (Gupta & Ali 2012).

Figure 1

FTIR spectra of PP and PP-MI showing the deposition of Fe on PP.

Figure 1

FTIR spectra of PP and PP-MI showing the deposition of Fe on PP.

Figure 2

XRD spectra of PP-MI. Potato peel (PP) did not show any XRD pattern due to the absence of any crystalline structure.

Figure 2

XRD spectra of PP-MI. Potato peel (PP) did not show any XRD pattern due to the absence of any crystalline structure.

Optimization of parameters

Sixteen experimental sets were applied for the removal of Pb2+ from the drinking water. Table 2 shows the %RE for each set. An overall %RE of 38–97 was obtained using these experimental sets. Based on the finding, experimental set 9 (Table 2) gives maximum %RE, i.e., 97%. It appeared that pH was an important parameter for controlling the process of adsorption. The increase in %RE indicated the competition of metal ions with H+ bound to the adsorbent surface. Table 2 showed that at 6 pH, only 10 min was required for the removal of Pb2+ from the solution which indicated that adequate active sites of adsorbent were available for the adsorption. Adsorbent dose (PP-MI) of 15 g/L gave maximum %RE because by increasing the quantity of PP-MI, more active sites are available to adsorb a large quantity of Pb2+. Although the initial concentration of Pb2+ was high (100 ppm), due to a large number of active sites of PP-MI, Pb2+ ions were easily removed. Based on the finding of DOE, contour maps (Figure 3) were plotted for %RE and predicted the best conditions for the removal of Pb2+. The plot of %RE between pH and adsorbent dose (PP-MI) (Figure 3(a)) suggested that pH 6 and dose value of 15 g/L gave up to 90% RE for Pb2+ whereas the same %RE can be obtained after 10 min and with 15 g/L of dose as per plot between time and adsorbent dose (Figure 3(b)). Furthermore, pH 6 and 15 g/L adsorbent dose along with 100 ppm concentration of Pb2+ also gave more than 90% removal efficiency of Pb2+ (Figure 3(d)).

Table 2

Removal efficiency of Pb2+ from drinking water using different experimental sets designed by the Taguchi method

Sr.pHTime (min)Dose (g/L)Conc. (ppm)RE%
1. 10 70 42 
2. 20 10 80 43 
3. 30 15 90 38 
4. 40 20 100 45 
5. 10 10 90 60 
6. 20 100 55 
7. 30 20 70 58 
8. 40 15 80 68 
9. 10 15 100 97 
10. 20 20 90 73 
11. 30 05 80 54 
12. 40 10 70 73 
13. 10 20 80 71 
14. 20 15 70 66 
15. 30 10 100 63 
16. 40 90 60 
Sr.pHTime (min)Dose (g/L)Conc. (ppm)RE%
1. 10 70 42 
2. 20 10 80 43 
3. 30 15 90 38 
4. 40 20 100 45 
5. 10 10 90 60 
6. 20 100 55 
7. 30 20 70 58 
8. 40 15 80 68 
9. 10 15 100 97 
10. 20 20 90 73 
11. 30 05 80 54 
12. 40 10 70 73 
13. 10 20 80 71 
14. 20 15 70 66 
15. 30 10 100 63 
16. 40 90 60 
Figure 3

Contour maps showing effects on removal efficiency using PP-MI: (a) pH vs dose of adsorbent; (b) time vs dose of adsorbent; (c) pH vs concentration of Pb2+; (d) dose of adsorbent vs concentration of Pb2+.

Figure 3

Contour maps showing effects on removal efficiency using PP-MI: (a) pH vs dose of adsorbent; (b) time vs dose of adsorbent; (c) pH vs concentration of Pb2+; (d) dose of adsorbent vs concentration of Pb2+.

Figure 4 was plotted using the Taguchi method result analysis and it confirmed that 6 pH (Figure 4(a)), 10 min time (Figure 4(b)), 15 g/L of adsorbent dose (Figure 4(c)), and 100 ppm Pb2+ (Figure 4(d)) concentration gave the maximum %RE. Further analysis of DOE results indicated that pH has a major effect on the %RE (Table 3) as it was ranked first in DOE result analysis. The significance of pH is also indicated by analysis of variance (ANOVA) (Table 4).

Table 3

Analysis design of experiments (DOE) by Taguchi method to check maximum effect of parameters for %RE of Pb2+

LevelpHTimeDoseConc.
32.45 36.20 34.37 35.35 
35.57 35.28 35.37 35.25 
37.23 34.37 36.09 35.00 
36.24 35.64 35.66 35.90 
Delta 4.78 1.82 1.72 0.90 
Rank 
LevelpHTimeDoseConc.
32.45 36.20 34.37 35.35 
35.57 35.28 35.37 35.25 
37.23 34.37 36.09 35.00 
36.24 35.64 35.66 35.90 
Delta 4.78 1.82 1.72 0.90 
Rank 
Table 4

Analysis of variance (ANOVA) for design of experiments (DOE) by Taguchi method for significance of parameters for %RE of Pb2+

SourceDFSeq SSAdj SSAdj MSFP
pH 2,206.3 2,206.3 735.42 15.09 0.026 
Time 416.2 416.2 138.75 2.85 0.207 
Dose 430.7 430.7 143.58 2.95 0.199 
Conc. 122.3 122.3 40.75 0.84 0.557 
SourceDFSeq SSAdj SSAdj MSFP
pH 2,206.3 2,206.3 735.42 15.09 0.026 
Time 416.2 416.2 138.75 2.85 0.207 
Dose 430.7 430.7 143.58 2.95 0.199 
Conc. 122.3 122.3 40.75 0.84 0.557 
Figure 4

Main effects plot for means of adsorption parameters for the removal of Pb2+ from drinking water: (a) pH; (b) time; (c) adsorbent dose; (d) concentration.

Figure 4

Main effects plot for means of adsorption parameters for the removal of Pb2+ from drinking water: (a) pH; (b) time; (c) adsorbent dose; (d) concentration.

All %RE of all parameters were analyzed and only the pH has significantp’ value while all other parameters showed ‘p’ values as not significant. This indicated that only the pH has a major effect on the removal of Pb2+ from drinking water using PP-MI particles.

Isotherm studies

Various isotherms, i.e., Langmuir isotherm, Freundlich isotherm, Temkin isotherm, Dubinin–Radushkevich (D-R) isotherm, and Flory–Huggins isotherm were used to study the mechanism of adsorption. These isotherms of adsorption are very important to discover the behavior of adsorbate on specific adsorbents. To find the maximum adsorption capacity of adsorbents, experiments are performed by varying metal ion concentrations and keeping all other parameters, i.e., pH (6), contact time (10 min), and adsorbent dose (15 g/L) at optimum. The isotherms show the relationship between the amount of Pb2+ taken up by per unit mass of adsorbent (qe) and the equilibrium concentration of adsorbate in the bulk fluid phase (Ce). Table 5 contains the information for the construction of these adsorption models.

Table 5

Mathematical models/equations for various isotherms used in the study

Sr.IsothermMathematical equationRef.
1. Langmuir  Jalees et al. (2019)  
2. Freundlich  
3. Temkin  
4. Dubinin–Radushkevich (D-R)  
5. Flory–Huggins  
Sr.IsothermMathematical equationRef.
1. Langmuir  Jalees et al. (2019)  
2. Freundlich  
3. Temkin  
4. Dubinin–Radushkevich (D-R)  
5. Flory–Huggins  

Equation (1): 1Ce: Equilibrium concentration of adsorbate (mg/L); qe: amount of metal adsorbed per gram of adsorbate at equilibrium; qm: maximum monolayer coverage capacity (mg/g); b: Langmuir isotherm constant.

Equation (2): Kf: Freundlich isotherm constant; n: adsorption intensity.

Equation (3): β: Temkin constant.

Equation (4): qs: theoretical isotherm saturation capacity; Kad: Dubnin–Radushkevich isotherm constant; ɛ: Dubnin–Radushkevich.

Equation (5): θ: degree of surface coverage; n: number of ions occupying adsorption sites; KFH: Flory–Huggin isotherm constant.

The Langmuir adsorption model was adopted for the homogenous monolayer adsorption process (Theivarasu & Mylsamy 2011). The model equation is given in Table 5. The linear plot of Ce vs Ce/qe is given in Figure 5. The values (Table 6) of qm and b were calculated using the slope and intercept of the plot (Figure 5(a)). The value of RL was less than zero, which suggested the adsorption was favorable (Theivarasu & Mylsamy 2011).

Table 6

Various constants and parameters calculated for different isotherm used for the removal study of Pb2+ using PP-IM

LangmuirFreundlichDubinin–Radushkevich
Slope 0.74 Slope −0.27 Slope 5.00 × 10−06 
Intercept −2.93 Intercept 0.32 Intercept 0.44 
Qmax 1.35 −3.67 5.00 
R2 0.99 Kf 2.09 Qm 1.55 
−0.25 R2 0.97 0.32 
RL −0.086 – – R2 0.85 
Temkin
Flory–Huggins
Slope −2.0 Slope −1.07   
Intercept 6.49 Intercept −5.64   
R2 0.98 R2 0.97   
Α 0.74 13.78   
Β 6.49 Kfh 35.42   
– – ΔG −12.81   
LangmuirFreundlichDubinin–Radushkevich
Slope 0.74 Slope −0.27 Slope 5.00 × 10−06 
Intercept −2.93 Intercept 0.32 Intercept 0.44 
Qmax 1.35 −3.67 5.00 
R2 0.99 Kf 2.09 Qm 1.55 
−0.25 R2 0.97 0.32 
RL −0.086 – – R2 0.85 
Temkin
Flory–Huggins
Slope −2.0 Slope −1.07   
Intercept 6.49 Intercept −5.64   
R2 0.98 R2 0.97   
Α 0.74 13.78   
Β 6.49 Kfh 35.42   
– – ΔG −12.81   
Figure 5

Isotherms’ response for the removal of Pb2+ using PP-IM: (a) Langmuir isotherm; (b) Freundlich isotherm; (c) Dubinin–Radushkevich isotherm; (d) Tempkin isotherm; (e) Florry Huggins isotherm. Calculated values for various isotherms are given in Table 6.

Figure 5

Isotherms’ response for the removal of Pb2+ using PP-IM: (a) Langmuir isotherm; (b) Freundlich isotherm; (c) Dubinin–Radushkevich isotherm; (d) Tempkin isotherm; (e) Florry Huggins isotherm. Calculated values for various isotherms are given in Table 6.

The Freundlich isotherm model was adopted to calculate adsorption intensity on the adsorbent surface. The plot of logCe vs logQe was used for this purpose (Figure 5(b)). The values of n and Kf were calculated from the slope and intercept of the graph, respectively. The value of n was smaller than zero, which suggested a favorable adsorption process.

The Dubinin–Radushkevich isotherm model was used for porosity and energy of adsorption measurements. The plot between ɛ2 vs LnQe was used (Figure 5(c)). The values of Kad and qm were calculated using the slope and intercept of the graph, respectively (Table 6). The value of E (mean free energy of adsorption) was 0.32 kJ/mol.

The Temkin isotherm model was used to predict the uniform distribution of binding energy over the population of surface binding adsorption (Theivarasu & Mylsamy 2011). The plot of LnCe vs Qe was used (Figure 5(d)). The values of α and β were calculated using the slope and intercept of the plot, respectively (Table 6).

The Flory–Huggins isotherm model was used for the degree of surface coverage of adsorbate on the adsorbent. The plot of Ln(1θ) vs Ln(θ/Co) was used (Figure 5(e)). The values of KFH and n can be calculated by slope and intercept, respectively (Table 6). The value of ΔG indicated a spontaneous exothermic condition.

Kinetics

Kinetics of removal of Pb2+ was studied at optimized condition (mentioned in the previous section) at a concentration of 60 ppm of Pb2+. The pseudo first order (Equation (6)) and pseudo second order (Equation (7)) kinetics were studied using the following equations (Jalees et al. 2019): 
formula
(6)
 
formula
(7)

The plot of t vs log(QeQt) and t vs T/Qt was used for pseudo first (Figure 6(a)) and second order (Figure 6(b)), respectively. Various kinetic parameters measured from these plots are given in Table 7. The regression values suggested that the adsorption followed pseudo second order kinetics as R2 value was very close to 1.

Table 7

Kinetics parameters for the removal of Pb2+ using PP-IM

Pseudo first orderPseudo second order
R2 0.367 R2 0.957 
Qe 0.454 Qe 0.254 
K1 0.003 K2 1.026 
Qe(exp) 0.353 Qe(exp) 0.353 
Pseudo first orderPseudo second order
R2 0.367 R2 0.957 
Qe 0.454 Qe 0.254 
K1 0.003 K2 1.026 
Qe(exp) 0.353 Qe(exp) 0.353 
Figure 6

Kinetics for the removal of Pb2+ using PP-MI: (a) pseudo first order; (b) pseudo second order.

Figure 6

Kinetics for the removal of Pb2+ using PP-MI: (a) pseudo first order; (b) pseudo second order.

Various researchers have used different nanoparticles for the removal of Pb2+ from drinking water (Table 8). A comparison of removal capacity by each methodology is given in Table 8. Simple nanoparticles to the composite nanoparticle, membrane/substrate supported nanoparticles, and bio-nanoparticles are available in the literature for the removal of Pb2+ in water. The removal capacity of PP-IM is better than the compared literature values which clearly indicates the good removal potential of PP-IM for Pb2+.

Table 8

Comparison of removal capacity of PP-IM for Pb2+

Adsorbent materialPb2+ (mg/g)Reference
PP-IM 97 Present study 
Fe nanoparticles using C. lemon peel 59.4 Lung et al. (2018)  
Fe iron particles 39 Moezzi et al. (2017)  
L-Cyst-Fe3O4 18.8 Bagbi et al. (2017)  
MgFe2O4–NH2 10 Nonkumwong et al. (2016)  
Polyaniline grafted chitosan 16.07 Karthik & Meenakshi (2015)  
Sulfur-modified magnetic nanoparticle 14.03 Jafarinejada et al. (2017)  
Nanostructured graphite oxide 82.59 Sheet et al. (2014)  
Magnesium oxide nanoparticles 21.78 Dargahi et al. (2016)  
Phyto-inspired iron oxide nanoparticles 93 Das & Rebecca (2018)  
Adsorbent materialPb2+ (mg/g)Reference
PP-IM 97 Present study 
Fe nanoparticles using C. lemon peel 59.4 Lung et al. (2018)  
Fe iron particles 39 Moezzi et al. (2017)  
L-Cyst-Fe3O4 18.8 Bagbi et al. (2017)  
MgFe2O4–NH2 10 Nonkumwong et al. (2016)  
Polyaniline grafted chitosan 16.07 Karthik & Meenakshi (2015)  
Sulfur-modified magnetic nanoparticle 14.03 Jafarinejada et al. (2017)  
Nanostructured graphite oxide 82.59 Sheet et al. (2014)  
Magnesium oxide nanoparticles 21.78 Dargahi et al. (2016)  
Phyto-inspired iron oxide nanoparticles 93 Das & Rebecca (2018)  

CONCLUSION

The use of agro-nanoparticles for the removal of Pb2+ from drinking water shows good results. Characteristic peaks of FTIR and XRD confirmed the deposition of MI on PP. The Taguchi design of experiment (16 experiments) was performed, which indicated that at pH 6, the contact time of 10 min and an adsorbent dose of 15 g/L can give more than 90% removal efficiency of Pb2+ using PP-MI. Contour maps, Taguchi response analysis, and ANOVA showed the dominant contribution of pH in the removal of Pb2+ from drinking water. Isotherm studies indicated that the adsorption process was favorable and consists of heterogeneous binding sites of multilayers adsorbent with 0.32 KJ/mol free energy as a spontaneous exothermic process. Kinetics studies showed that the adsorption process was followed by pseudo second order kinetics. A comparison of the sorption capacity of PP-MI for Pb2+ with literature values suggested that PP-MI has good potential for the removal of Pb2+ from drinking water. The overall results indicated that the use of potato peel (considered as waste) as a substrate for nanoparticles will be helpful in the treatment of heavy metals in water.

REFERENCES

REFERENCES
Abbas
A.
Al-Amer
A. M.
Laoui
T.
Al-Marri
M. J.
Nasser
M. S.
Khraisheh
M.
Atieh
M. A.
2016
Heavy metal removal from aqueous solution by advanced carbon nanotubes: critical review of adsorption applications
.
Separation and Purification Technology
157
,
141
161
.
American Public Health Association
2005
3500 B Pb Standard Methods for the Examination of Water and Wastewater
.
American Public Health Association (APHA)
,
Washington, DC
,
USA
.
Bagbi
Y.
Sarswat
A.
Mohan
D.
Pandey
A.
Solanki
P. R.
2017
Lead and chromium adsorption from water using L-cysteine functionalized magnetite (Fe3O4) nanoparticles
.
Scientific Reports
7
(
1
),
7672
.
doi:10.1038/s41598-017-03380-x
.
Banerjee
S. S.
Chen
D.-H.
2007
Fast removal of copper ions by gum arabic modified magnetic nano-adsorbent
.
Journal of Hazardous Materials
147
(
3
),
792
799
.
Dargahi
A.
Golestanifar
H.
Darvishi
P.
Karami
A.
Hasan
S. H.
Poormohammadi
A.
Behzadnia
A.
2016
An investigation and comparison of removing heavy metals (lead and chromium) from aqueous solutions using magnesium oxide nanoparticles
.
Polish Journal of Environmental Studies
25
(
2
),
557
562
.
Das
M. P.
Rebecca
L. J.
2018
Removal of lead (II) by phyto-inspired iron oxide nanoparticles
.
Nature Environment and Pollution Technology
17
(
2
),
569
574
.
Dawodu
F.
Akpomie
G.
Ogbu
I.
2012
Isotherm modeling on the equilibrium sorption of cadmium (II) from solution by agbani clay
.
International Journal of Multidisciplinary Science and Engineering
3
(
9
),
9
14
.
Dubois
M.
Gilles
K. A.
Hamilton
J. K.
Rebers
P. T.
Smith
F.
1956
Colorimetric method for determination of sugars and related substances
.
Analytical Chemistry
28
(
3
),
350
356
.
Feng
Y.
Gong
J.-L.
Zeng
G.-M.
Niu
Q.-Y.
Zhang
H.-Y.
Niu
C.-G.
Deng
J.-H.
Yan
M.
2010
Adsorption of Cd (II) and Zn (II) from aqueous solutions using magnetic hydroxyapatite nanoparticles as adsorbents
.
Chemical Engineering Journal
162
(
2
),
487
494
.
Gebrechristos
H. Y.
Chen
W.
2018
Utilization of potato peel as eco-friendly products: a review
.
Food Science & Nutrition
6
(
6
),
1352
1356
.
Gupta
V. K.
Ali
I.
2004
Removal of lead and chromium from wastewater using bagasse fly ash – a sugar industry waste
.
Journal of Colloid and Interface Science
271
(
2
),
321
328
.
Gupta
V. K.
Ali
I.
2012
Environmental Water: Advances in Treatment, Remediation and Recycling
.
Elsevier
,
Amsterdam
,
The Netherlands
.
Jafarinejada
S.
Farajib
M.
Jafaria
P.
Mokhtari-Aliabadc
J.
2017
Removal of lead ions from aqueous solutions using novel-modified magnetic nanoparticles: optimization, isotherm, and kinetics studies
.
Desalination and Water Treatment
92
,
267
274
.
Jalees
M. I.
Farooq
M. U.
Basheer
S.
Asghar
S.
2019
Removal of heavy metals from drinking water using Chikni Mitti (kaolinite): isotherm and kinetics
.
Arabian Journal for Science and Engineering
.
https://doi.org/10.1007/s13369-019-03722-z
Mackay
D.
Shiu
W. Y.
Ma
K.-C.
1997
Illustrated Handbook of Physical-Chemical Properties of Environmental Fate for Organic Chemicals
, Vol.
5
.
CRC Press
,
Boca Raton, FL
,
USA
.
Mahdavi
S.
Jalali
M.
Afkhami
A.
2013
Heavy metals removal from aqueous solutions using TiO2, MgO, and Al2O3 nanoparticles
.
Chemical Engineering Communications
200
(
3
),
448
470
.
Moezzi
A.
Soltanali
S.
Torabian
A.
Hassani
A.
2017
Removal of lead from aquatic solution using synthesized iron nanoparticles
.
International Journal of Nanoscience and Nanotechnology
13
(
1
),
83
90
.
Mohammed
E.
Bouazza
T.
Khalil
E.-H.
2018
Structural and vibrational study of hydroxyapatite bio-ceramic pigments with chromophore ions (Co2+, Ni2+, Cu2+, Mn2+)
. In:
Advanced Intelligent Systems for Sustainable Development, AI2SD 2018
(
Ezziyyani
M.
eds).
Advances in Intelligent Systems and Computing, Springer
,
Cham
,
Switzerland
, pp.
62
70
.
Oukebdane
K.
Belyouci
O.
Didi
M. A.
2018
Liquid-solid adsorption of Cd (II) by maghemite
.
Current Nanomaterials
3
(
2
),
95
102
.
Panuccio
M. R.
Sorgonà
A.
Rizzo
M.
Cacco
G.
2009
Cadmium adsorption on vermiculite, zeolite and pumice: batch experimental studies
.
Journal of Environmental Management
90
(
1
),
364
374
.
Rao
B. S.
Kalahasti
S.
Rao
E. V.
Prasad
K. R.
Sandhya
J.
2019
Polymer nano composites for water pollution applications
.
Journal of Water Pollution & Purification Research
5
(
3
),
7
9
.
Rice
E.
Baird
R.
Eaton
A.
2017
Standard Methods for the Examination of Water and Wastewater
.
American Water Works Association
,
Washington, DC
,
USA
.
Theivarasu
C.
Mylsamy
S.
2011
Removal of malachite green from aqueous solution by activated carbon developed from cocoa (Theobroma Cacao) shell-A kinetic and equilibrium studies
.
Journal of Chemistry
8
(
S1
),
S363
S371
.