- Open Access
Nanoscale zero-valent iron-impregnated agricultural waste as an effective biosorbent for the removal of heavy metal ions from wastewater
© Kumar et al. 2016
Received: 16 December 2015
Accepted: 3 March 2016
Published: 15 March 2016
A novel, nanoscale zero-valent iron-impregnated cashew nut shell (NZVI-CNS) was synthesized towards the removal of Ni(II) ions from aqueous solution using impregnation procedure. The factors affecting Ni(II) ion adsorption in a batch mode were studied including the initial metal ion concentration, solution pH, temperature, adsorbent dosage, and contact time. The adsorption isotherm and kinetics could be described well with Freundlich and pseudo first-order, respectively. The maximum monolayer adsorption capacity for the removal of Ni(II) ions was found to be 70.05 mg/g. The calculated thermodynamic parameters showed that the removal of Ni(II) ions by the NZVI-CNS was spontaneous, feasible, and exothermic in nature. The amount of adsorbent needed to treat the known volume of the effluent was calculated by using single-stage batch adsorber design. The experimental results specifies that the NZVI-CNS have a high adsorption capacity for the removal of Ni(II) ions from aqueous solution.
In recent decades, industrialization and urbanization have grown exponentially to meet the human needs. As a result, the environmental impact has been increasing dramatically due to the direct discharge of toxic effluent into the water bodies. The toxic substances are mostly hazardous to human health which includes heavy metals, pharmaceuticals, pesticides, and dyes. Among which, heavy metals received a special attention by many researchers because they are persistent nature due to lack of biodegradability (Martins et al. 2013; Singh and Das 2013; Gong et al. 2013). In recent years, these heavy metals play a vital role in most of the industries. Particularly, nickel is widely used in diverse metal products and processes. Few of their applications are in industries such as electroplating, batteries manufacturing, mining, metal finishing, porcelain enameling, and paint formulations. The toxicity of nickel ions will cause severe health issues such as dermatitis, allergies, renal disturbances, hepatitis, infertility, lung cancer, stomatitis, gingivitis, insomnia, nauseas, and different poisoning degrees to the kidney and cardiovascular system (Paulino et al. 2007; Fu et al. 2015; Jeon and Cha 2015). Hence, the effluents with nickel ions should be treated before letting them into the receiving water bodies. According to the US EPA, the permissible limit of nickel in wastewater effluent is 2 mg/L for short-term effluent reuse and 0.2 mg/L for long-term effluent reuse (El-Sadaawy and Abdelwahab 2014; U.S EPA 2004). According to the Bureau of Indian Standards, the maximum permissible limit for Ni(II) ions in drinking water has been fixed at 0.02 mg/L (BIS 1994). Therefore, many technologies such as chemical precipitation (Purkayastha et al. 2014), ion exchange, electrochemical technologies (Fu and Wang 2011), adsorption (Bilal et al. 2013), and membrane filtration process such as microfiltration (Tashvigh et al. 2015), reverse osmosis (Wei et al. 2014), ultrafiltration (Tanhaei et al. 2014), nanofiltration (Alzahrani and Mohammad 2014), and electrodialysis (Dermentzis 2010) have been employed for both removal and recovery of Ni(II) ion from aqueous environment. Most of these technologies are expensive and incompatibility to remove the trace level of heavy metal ions. Among these technologies, many researchers focused on adsorption technology which offers simplicity, technical feasibility, economical viability, and social acceptability and also got high removal efficiency of heavy metal from aqueous solution. On the other hand, the main advantage of this process is reversible, because the adsorbents used for metal ions removal can be regenerated by employing appropriate desorption process (Barakat 2011; Zhou et al. 2015; Mahmoud et al. 2015). The commercial adsorbent such as activated carbons (Rajkumar et al. 2014), polymeric materials (Anitha et al. 2015), clays (Lee and Tiwari 2012), biosorbents (Kumar et al. 2015), and other adsorbents have been commonly used for this adsorption process. Many adsorbents usually have lower adsorption capacity, higher cost, longer equilibrium time, poor regeneration abilities, and separation problems (Prabu et al. 2015, 2016). Hence, adsorbents qualifying the aforementioned problems were synthesized and employed for removal of metal ions from aqueous environment.
Nanoscale zero-valent iron (NZVI) is a promising technology because many researchers focused on this process and implemented in the treatment of hazardous contaminants from wastewater. This increase in interest on the use of NZVI is owing to its higher surface area, lower cost, non-toxic, and higher reactivity (Uzum et al. 2009; Boparai et al. 2011; Arshadi et al. 2014; Prabu et al. 2016). The removal mechanism is directional transfer of electrons from NZVI to the contaminants and then the contaminant is transformed into non-toxic or less-toxic species. In addition, it also degrades and oxidize the organic compounds in the presence of dissolved oxygen (DO) (Fu et al. 2014; Prabu et al. 2015, 2016). Mostly, direct of use of NZVI is restricted due to its lack of stability, easy aggregation, and facing difficulties in separating NZVI from treated effluents. To mitigate these issues, NZVI is impregnated with supporting material such as cashew nut shell (CNS) with the help of sonication operation. This does not only provide better operation but enhances the reduction ability of NZVI (Fu et al. 2014; Prabu et al. 2016). Finally, the efficient removal of nickel ions in aqueous environment can be achieved by utilizing the synthesized nanoscale zero-valent iron-impregnated cashew nut shell (NZVI-CNS). In this research, the batch adsorption studies for the removal of Ni(II) ions were investigated by using the several parameters such as initial Ni(II) concentration, solution pH, temperature, adsorbent dose, and contact time. The adsorption isotherm, kinetics, design, and thermodynamic studies have been discussed to explain the adsorption process.
Chemicals and equipment
The chemical nickel(II) sulfate hexahydrate [NiSO4·6H2O] was used to prepare the stock solution of Ni(II) ions. The nickel salt was taken in a measured amount and diluted in double distilled water. To make the desired Ni(II) ions concentration solution (25–150 mg/L), the stock solution was further diluted with distilled water. The pH of the different ion concentration solution was measured with a pH meter (Elico Limited, India) and was adjusted using 0.1 N NaOH and 0.1 N HCL solutions. The concentration of Ni(II) ions onto the ions solution before and after adsorption process was measured with an atomic adsorption spectrophotometer (AAS, SL 176 Model, Elico Limited, Chennai, India).
Preparation of the adsorbent
The CNS system was completely washed using distilled water followed by a wash with methanol to prevent the corrosion formation. At last, the CNS system was dried and stored in an oxygen-free nitrogen environment. This prepared material was abbreviated as NZVI-CNS (NZVI-impregnated CNS). During the synthesis of ZVI, the particles of boron were formed. These particles are toxic in nature, so special care must be needed for separating the boron particles.
Batch adsorption studies
where C o (mg/L) and C e (mg/L) are the initial and equilibrium concentrations of Ni(II) ion solution, respectively.
Adsorption equilibrium experiments
The adsorption isotherm studies were performed in a series of 100 mL Erlenmeyer flasks by adding 0.2 g of adsorbent material (NZVI-CNS) into 100 mL of the Ni(II) ion solution with the various initial Ni(II) ion concentrations in the range of 25 to 150 mg/L at an optimum condition, and then, the mixtures were kept in a temperature-controlled shaking incubator until its equilibrium time. Once the equilibrium time is reached, the flasks were withdrawn from the incubation shaker and the adsorbent material NZVI-CNS was centrifuged to separate the supernatant and the spent adsorbent. The concentration of Ni(II) ion in the supernatant was examined by using atomic adsorption spectrophotometer (AAS) (SL 176 Model, Elico Limited, Chennai, India), and the values are substituted in the following formula to know the amount of Ni(II) ion adsorbed onto the NZVI-CNS at equilibrium, q e (mg/g).
where C o and C e are the concentrations of Ni(II) ions in the solution initially and at equilibrium (mg/g), respectively, V is the volume of the Ni(II) ion solution (L), and m is the mass of the adsorbent (g).
The two-parameter and the three-parameter isotherm models were used to explain the Ni(II) ions adsorption towards the selected adsorbent. The different parameters, R 2, and the error values are analyzed by the MATLAB R2009a software.
where q e is the adsorption capacity at equilibrium (mg/g), q m is the maximum monolayer adsorption capacity (mg/g), C e is the concentration of the metal ions at equilibrium (mg/L), and K L is the Langmuir equilibrium constant (L/mg).
where C e is the concentration of the metal ions at equilibrium (mg/L), K F is the Freundlich constant [(mg/g)(L/mg)(1/n)] related to the bonding energy, and n is a measure of deviation from the linearity of adsorption (g/L). The significance of “n” is as follows: n = 1 (linear), n > 1 (physical process), and n < 1 (chemical process).
where C e is the concentration of metal ions at equilibrium (mg/L), β RP is the exponent which lies between 0 and 1, K RP is the Redlich-Peterson isotherm constant (L/g), α RP is the Redlich-Peterson isotherm constant (L/mg)1/β RP. The significance of β is as given as follows: β = 1 (Langmuir adsorption isotherm model is a preferable adsorption isotherm model) and β = 0 (Freundlich adsorption isotherm model is a preferable adsorption isotherm model).
where K s is the Sips model isotherm constant (L/g) βS, α s is the Sips model constant (L/g)1/βS, and β S is often regarded as the heterogeneity factor, with values close to 1 indicating a homogeneous binding site and values greater than 1 indicating a heterogeneous adsorption system.
Adsorption kinetic experiments
where q t is the amount of Ni(II) ions adsorbed by the adsorbent at any time (mg/g), C t is the concentration of Ni(II) ions at particular time (mg/L), V is the volume of the metal ion solution (L), and m is the mass of the adsorbent (g).
The pseudo first-order, pseudo second-order, and Elovich kinetic models are used to determine the rate of the adsorption process.
where q t is the adsorption capacity at any time (mg/g), q e is the equilibrium adsorption capacity (mg/g), k 1 is the pseudo first-order kinetic rate constant (min−1), and t is the time (min).
where k 2 is the pseudo second-order kinetic rate constant (g/mg min) and t is the time (min).
where β E is the desorption constant related to the activation energy of chemisorption (g/mg) and α E is the initial adsorption rate (mg/(g min)).
Adsorption thermodynamic study
where C Ae is the amount of Ni(II) ions adsorbed onto the adsorbent per liter of solution at equilibrium (mg/L), C e is the equilibrium concentration in solution (mg/L), T is the temperature (K), R is the gas constant (8.314 J/mol/K), and K c is the equilibrium constant. The values of ∆S o and ∆H o were calculated from the slope and the intercept of the plot of log K c versus 1/T.
Results and discussions
Influence of initial Ni(II) ion concentration on the adsorption of Ni(II) ions and adsorption isotherms
Isotherm constants of the two-parameter and three-parameter models for the removal of Ni(II) ions by NZVI-CNS
q m (mg/g)
K L (L/mg)
K F [(mg/g)(L/mg)(1/n))]
K RP (L/g)
α RP (L/mg)(1/βRP)
K S (L/g) βs
α s (L/mg)(βs)
Influence of solution pH on the adsorption of Ni(II) ions
Influence of temperature on the adsorption of Ni(II) ions and thermodynamic studies
Thermodynamic parameters for the adsorption of Ni(II) ions onto NZVI-CNS
Concentration of Ni(II) ion solution (mg/L)
∆G o (kJ/mol)
Influence of adsorbent dosage on the adsorption of Ni(II) ions
Influence of contact time on the adsorption of Ni(II) ions and kinetic studies
Adsorption kinetic data for the removal of Ni(II) ions by NZVI-CNS
Adsorption kinetic model
q e (mg/g)
q e, exp (mg/g)
k 1 (min−1)
q e, cal (mg/g)
k 2 (g/mg min)
Elovich kinetic model
α E mg/(g min)
β E (g/mg)
Design of a single-stage batch adsorber
In summary, we reported that the NZVI-CNS adsorbent material was successfully synthesized through the impregnated method which have been effectively used for the removal of Ni(II) ions from aqueous solution. The adsorption was studied kinetically using diverse adsorption kinetic models such as pseudo first-order, pseudo second-order, and Elovich kinetic models. The results showed that the adsorption process followed the pseudo first-order model based on higher correlation coefficient with low error values. The adsorption of Ni(II) ions onto NZVI-CNS was influenced by several operating parameters such as initial Ni(II) ion concentration, solution pH, contact time, temperature, and adsorbent loading. The maximum monolayer adsorption capacity for the removal of Ni(II) ions was found to be 70.05 mg/g at an optimum condition. The equilibrium isotherm has been analyzed using different isotherm models such as Langmuir, Freundlich, Redlich-Peterson, and Sips model. Among these, the Freundlich isotherm model was identified as a well-suitable adsorption isotherm model based on the high coefficient of determination values with low error values. The adsorption thermodynamics illustrated that the electrostatic interaction plays an important role in the adsorption process. The values of thermodynamic parameters such as Gibbs free energy, entropy, and enthalpy indicated that the adsorption process was spontaneous, feasible, and exothermic in nature. A batch adsorber was designed to determine the amount of adsorbent dose needed for the treatment of a known volume of the desired Ni(II) ion concentration. Based on the experimental studies, it can be concluded that the NZVI-CNS materials has more potential for the removal of Ni(II) ions, and correspondingly for many other heavy metal ions from aqueous solution, with the advantages of being low cost, recyclable, efficient, and economically friendly.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Aliabadi, M., Irani, M., Ismaeili, J., Piri, H., & Parnian, M. J. (2013). Electrospun nanofiber membrane of PEO/chitosan for the adsorption of nickel, cadmium, lead and copper ions from aqueous solution. Chemical Engineering Journal, 220, 237–243.View ArticleGoogle Scholar
- Alzahrani, S., & Mohammad, A. W. (2014). Challenges and trends in membrane technology implementation for produced water treatment: a review. Journal of Water Process Engineering, 4, 107–133.View ArticleGoogle Scholar
- Anitha, T., Kumar, P. S., & Kumar, S. (2015). Binding of Zn(II) ions to chitosan-PVA blend in aqueous environment: adsorption kinetics and equilibrium studies. Environmental Progress & Sustainable Energy, 34, 15–22.View ArticleGoogle Scholar
- Arshadi, M., Soleymanzadeh, M., Salvacion, J. W. L., & SalimiVahid, F. (2014). Nanoscale zero-valent iron (NZVI) supported on sineguelas waste for Pb(II) removal from aqueous solution: kinetics, thermodynamic and mechanism. Journal of Colloid and Interface Science, 426, 241–251.View ArticleGoogle Scholar
- Barakat, M. A. (2011). New trends in removing heavy metals from industrial wastewater. Arabian Journal of Chemistry, 4, 361–377.View ArticleGoogle Scholar
- Bilal, M., Shah, J. A., Ashfaq, T., Gardazi, S. M. H., Tahir, A. A., Pervez, A., Haroon, H., Mahmood, Q. (2013). Waste biomass adsorbents for copper removal from industrial wastewater—a review. Journal of Hazardous Materials, 263, 322–333.View ArticleGoogle Scholar
- BIS. (1994). Methods of sampling and test (physical and chemical) for water and waste water. Part 54 Nickel. IS No. 3025.Google Scholar
- Boparai, K. H., Joseph, M., & O’Carroll, D. M. (2011). Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles. Journal of Hazardous Materials, 186, 458–465.View ArticleGoogle Scholar
- Dermentzis, K. (2010). Removal of nickel from electroplating rinse waters using electrostatic shielding electrodialysis/electrodeionization. Journal of Hazardous Materials, 173, 647–652.View ArticleGoogle Scholar
- El-Sadaawy, M., & Abdelwahab, O. (2014). Adsorptive removal of nickel from aqueous solutions by activated carbons from doum seed (Hyphaenethebaica) coat. Alexandria Engineering Journal, 53, 399–408.View ArticleGoogle Scholar
- Fan, T., Liu, Y. G., Feng, B. Y., Zeng, G. M., Yang, C. P., Zhou, M., Zhou, HZ., Tan, ZF., Wang, X. (2008). Biosorption of cadmium(II), zinc(II) and lead(II) by Penicillium simplicissimum: isotherms, kinetics and thermodynamics. Journal of Hazardous Materials, 160, 655–661.View ArticleGoogle Scholar
- Freundlich, H. M. F. (1906). Over the adsorption in solution. Journal of Physical Chemistry, 57, 385–470.Google Scholar
- Fu, F., & Wang, Q. (2011). Removal of heavy metal ions from wastewaters: a review. Journal of Environmental Management, 92, 407–418.View ArticleGoogle Scholar
- Fu, F., Dionysiou, D. D., & Liu, H. (2014). The use of zero-valent iron for groundwater remediation and wastewater treatment: a review. Journal of Hazardous Materials, 267, 194–205.View ArticleGoogle Scholar
- Fu, Y., Wu, J., Zhou, H., & Jin, G. (2015). Removal of nickel(II) from aqueous solutions using iminodiacetic acid functionalized polyglycidyl methacrylate grafted-carbon fibers. Chinese Journal of Chemical Engineering, 23, 919–923.View ArticleGoogle Scholar
- Gao, J., Liu, F., Ling, P., Lei, J., Li, L., Li, C., Li, A. (2013). High efficient removal of Cu(II) by a chelating resin from strong acidic solutions: complex formation and DFT certification. Chemical Engineering Journal, 222, 240–247.View ArticleGoogle Scholar
- Gong, X., Li, W., Wang, K., & Hu, J. (2013). Study of the adsorption of Cr(VI) by tannic acid immobilized powdered activated carbon from micro-polluted water in the presence of dissolved humic acid. Bioresource Technology, 141, 145–151.View ArticleGoogle Scholar
- Ho, Y. S., & McKay, G. (1999). Pseudo-second order kinetic model for sorption processes. Process Biochemistry, 34, 451–465.View ArticleGoogle Scholar
- Jeon, C., & Cha, J. H. (2015). Removal of nickel ions from industrial wastewater using immobilized sericite beads. Journal of Industrial and Engineering Chemistry, 24, 107–112.View ArticleGoogle Scholar
- Jiang, N., Xu, Y., Dai, Y., Luo, W., & Dai, L. (2012). Polyaniline nanofibers assembled alginate microsphere for Cu2+ and Pb2+ uptake. Journal of Hazardous Materials, 215–216, 17–24.View ArticleGoogle Scholar
- Karami, H. (2013). Heavy metal removal from water by magnetite nanorods. Chemical Engineering Journal, 219, 209–216.View ArticleGoogle Scholar
- Kumar, P.S., Pavithra, J., Suriya, S., Ramesh, M., Kumar, K.A. (2015). Sargassum wightii, a marine alga is the source for the production of algal oil, bio-oil, and application in the dye wastewater treatment. Desalination and Water Treatment, 55, 1342–1358.Google Scholar
- Lagergren, S. (1898). About the theory of so-called adsorption of soluble substances. Kungliga Svenska Vetensk Handl, 24, 1–39.Google Scholar
- Langmuir, I. (1918). The adsorption of gases on plane surfaces of glass, mica and platinum. Journal of American Chemical Society, 40, 1361–1368.View ArticleGoogle Scholar
- Lata, H., Garg, V., & Gupta, R. (2008). Adsorptive removal of basic dye by chemically activated Parthenium biomass: equilibrium and kinetic modeling. Desalination, 219, 250–261.View ArticleGoogle Scholar
- Lee, S. M., & Tiwari, D. (2012). Organo and inorgano-organo-modified clays in the remediation of aqueous solution: an overview. Applied Clay Science, 59–60, 84–102.View ArticleGoogle Scholar
- Li, X., Qi, Y., Li, Y., Zhang, Y., He, X., & Wang, Y. (2013). Novel magnetic beads based on sodium alginate gel crosslinked by zirconium(IV) and their effective removal for Pb2+ in aqueous solutions by using a batch and continuous systems. Bioresource Technology, 142, 611–619.View ArticleGoogle Scholar
- Low, M. J. D. (1960). Kinetics of chemisorption of gases on solids. Chemical Reviews, 60, 267–312.View ArticleGoogle Scholar
- Mahmoud, A. M., Ibrahim, F. A., Shaban, S. A., & Youssef, N. A. (2015). Adsorption of heavy metal ion from aqueous solution by nickel oxide nano catalyst prepared by different methods. Egyptian Journal of Petroleum, 24, 27–35.View ArticleGoogle Scholar
- Martins, A. E., Pereira, M. S., Jorgetto, O. A., Martines, M. A. U., Silva, R. I. V., Saeki, M. J., Castro, GR. (2013). The reactive surface of castor leaf [Ricinus communis L.] powder as a green adsorbent for the removal of heavy metals from natural river water. Applied Surface Science, 276, 24–30.View ArticleGoogle Scholar
- Paulino, A. T., Guilherme, M. R., Reis, A. V., Tambourgi, E. B., Nozaki, J., & Muniz, E. C. (2007). Capacity of adsorption of Pb2+ and Ni2+ from aqueous solution by chitosan produced from silkworm chrysalides in different degrees of deacetylation. Journal of Hazardous Materials, 147, 139–147.View ArticleGoogle Scholar
- Prabu, D., Parthiban, R., Kumar, P. S., & Namasivayam, S. K. R. (2015). Synthesis, characterization and antibacterial activity of nano zero-valent iron impregnated cashew nut shell. International Journal of Pharmacy and Pharmaceutical Science, 7, 139–141.Google Scholar
- Prabu, D., Parthiban, R., Kumar, P.S., Kumari, N., Saikia, P. (2016). Adsorption of copper ions onto nano-scale zero-valent iron impregnated cashew nut shell. Desalination and Water Treatment, 57, 6487–6502.Google Scholar
- Purkayastha, D., Mishra, U., & Biswas, S. (2014). A comprehensive review on Cd(II) removal from aqueous solution. Journal of Water Process Engineering, 2, 105–128.View ArticleGoogle Scholar
- Rajkumar, P., Kumar, P. S., Priyadharshini, M., Kirupha, S. D., Baskaralingam, P., & Sivanesan, S. (2014). Removal of Cu(II) ions from aqueous solution by adsorption onto activated carbon produced from Guazumaulmifolia seeds. Environmental Engineering and Management Journal, 13, 905–914.Google Scholar
- Redlich, O., & Peterson, D. L. (1959). A useful adsorption isotherms. Journal of Physical Chemistry, 63, 1024–1026.View ArticleGoogle Scholar
- Singh, B., & Das, S. K. (2013). Adsorptive removal of Cu(II) from aqueous solution and industrial effluent using natural/agricultural wastes. Colloids and Surfaces B: Biointerfaces, 107, 97–106.View ArticleGoogle Scholar
- Sips, R. (1948). On the structure of a catalyst surface. Journal of Physical Chemistry, 16, 490–495.View ArticleGoogle Scholar
- Tanhaei, B., Chenar, M. P., Saghatoleslami, N., Hesampour, M., Kallioinen, M., Sillanpaa, M., Manttari, M. (2014). Removal of nickel ions from aqueous solution by micellar-enhanced ultrafiltration, using mixed anionic-non-ionic surfactants. Separation and Purification Technology, 138, 169–176.View ArticleGoogle Scholar
- Tashvigh, A. A., Fouladitajar, A., & Ashtiani, F. Z. (2015). Modeling concentration polarization in crossflow microfiltration of oil-in-water emulsion using shear-induced diffusion; CFD and experimental studies. Desalination, 357, 225–232.View ArticleGoogle Scholar
- U.S EPA. (2004). Guidelines for water reuse, EPA/625/R-04/108, U.S. Agency for Inter. Development, Washington, DC, USA.Google Scholar
- Uzum, C., Shahwan, T., Eroglu, A. E., Hallam, K. R., Scott, T. B., & Lieberwirth, I. (2009). Synthesis and characterization of kaolinite-supported zero-valent iron nanoparticles and their application for the removal of aqueous Cu2+ and Co2+ ions. Applied Clay Science, 43, 172–181.View ArticleGoogle Scholar
- Wei, X., Gu, P., & Zhang, G. (2014). Reverse osmosis concentrate treatment by a PAC countercurrent four-stage adsorption/MF hybrid process. Desalination, 352, 18–26.View ArticleGoogle Scholar
- Zhou, G., Liu, C., Tang, Y., Luo, S., Zeng, Z., Liu, Y., Xu, R., Chu, L. (2015). Sponge-like polysiloxane-graphene oxide gel as a highly efficient and renewable adsorbent for lead and cadmium metals removal form wastewater. Chemical Engineering Journal, 280, 275–282.View ArticleGoogle Scholar