Removal of Ni2+ from aqueous solution by adsorption onto maize tree-Trunk polyaniline composite - Pham Viet Tien

Vietnam Journal of Chemistry, International Edition, 54(4): 429-433, 2016 DOI: 10.15625/0866-7144.2016-00341 429 Removal of Ni2+ from aqueous solution by adsorption onto maize tree-trunk polyaniline composite Pham Viet Tien 1 , Mai Thi Thanh Thuy 2 , Nguyen Thi Van Anh 2 , Mai Thi Xuan 2 , Pham Thi Tot 2 , Le Cao The 3 , Phan Thi Binh 2* 1 VQB Mineral and Trading Group Joint Stock Company 2 Institute of Chemistry, Vietnam Academy of Science and Technology 3 Center for Survey and Analysis of Environmental Resources, Environmental resource base Hanoi Received 23 May 2016; Accepted for publication 12 August 2016 Abstract Maize tree-trunk polyaniline composite was prepared by chemical polymerization method. Function groups belonging to materials were characterized by IR analysis and their morphological structure was examined by SEM image. The adsorption of Ni 2+ was carried out onto composite in aqueous solution via varying pH, contact time and its initial concentration. The experimental adsorption data fitted into Freundlich adsorption isotherm model (r 2 = 0.9898) better than into Langmuir one (r 2 = 0.6764). The adsorption followed pseudo-second order kinetic model very well (r 2 = 0.9976). The maximum adsorption capacity of that composite was 66.67 mg/g which calculated from the pseudo- Langmuir equation. Keywords. Maize tree-trunk polyaniline composite, removal of Ni 2+ , isotherm and kinetic adsorptions. 1. INTRODUCTION Removal of heavy metal ions from aqueous solution has been regarding mostly by scientists because of human health on the world which is damaged by strongly developing many industrial branches such as metallurgy, electroplating and trade village. All of them are resulting to critical environmental pollution in air or groundwater. Ni 2+ ion is one of the most toxic chemical agents, therefore, many methods as well as adsorbents were regarded to find out for removing it from wastewater [1-4]. Among them the adsorption method is economic and efficient way because of inexpensive adsorbents and sample treatment process. Polyaniline (PANi) is one of the most promising polymer which is used widely to fabricate composites based on it and agriculture waste for removing heavy metal ions from wastewater [5-8] because of its stable environmental conductive property and easy regeneration. The main objective of this work was to evaluate the adsorption isotherms for Ni 2+ ion onto Maize tree-trunk polyaniline composite which prepared by chemical method. 2. EXPERIMENTAL 2.1. Synthesis procedure of Maize tree-trunk polyaniline composite Carrying agent was prepared from maize tree- trunk (MTT) following procedure: it was firstly tried and then ground in micro size (< 100 μm). Continuously, it was ultrasonic for 20 minutes in acetone solution, then filtrated and washed by distilled water. Lastly, it was tried under vacuum at 50 o C until completely dry before use. Maize tree- trunk polyaniline (MTT-PANi) composite based on MTT and PANi was prepared by chemical method from acid medium containing aniline using ammonium persulfate as an oxidation agent. The reaction occurred in 18 h under continuous stirring at temperature of 1÷5 o C. After purification and changing it into emeraldine base (EB) by treatment with 0.5 M ammonia solution, it was dried in vacuum at 50-60 o C for 4-5 h and kept in a sealed bottle for adsorption of nickel ion. 2.2. Ni 2+ adsorption The pH effect was considered by varying pH from 1 to 7 when initial nickel concentration (C0) was kept 1 mg/L with contact time of 40 min. The VJC, 54(4) 2016 Phan Thi Binh, et al. 430 effect of contact time t (min) was investigated at C0 = 1 mg/L and pH = 6 by t varied from 10 to 100 min. The effect of C0 was studied at pH = 6 and t = 40 min due to changing C0 from 0 to 2.235 mg/L. Ni 2+ concentrations in solution before and after adsorption onto adsorbent were analyzed by Atomic Absorption Spectroscopy (AAS) from which the adsorption amount could be calculated. The adsorption capacity (qt, mg/g) and the removal efficiency (H, %) were calculated from the following equations: 0 ( )t t C C V q m (1) 0 0 ( ) .100%t C C H C (2) Where C0 and Ct are the concentration of Ni 2+ (mg/L) initially and at time t (min), respectively; V is the volume of the solution (mL), m is the mass of adsorbent (g). The pseudo–first and second order kinetic models [8, 9] (equations 3 and 4, respectively) were used for analyzing kinetics and rate of Ni 2+ adsorption onto MTT-PANi. log(qe – qt) = logqe - 1 2.303 k t (3) 2 2 1 t e e t t q k q q (4) Where qe and qt are the adsorption capacity of Ni 2+ onto MTT-PANi at equilibrium and contact time t. The equilibrium rate constants of pseudo- first and second order adsorption are k1 and k2, respectively. Based on the parameters of second - order adsorption kinetic model (equation 4), the equilibrium concentration of Ni 2+ in solution can be calculated from the equation below: 0 e e q m C C V (5) Where qe is the equilibrium adsorption capacity obtained from pseudo - second order rate law (mg/g), V is solution volume (L), m is mass of adsorbent (g), Ce and C0 are the equilibrium and initial concentration in solution (mg/L), respectively. The Langmuir (6) and Freundlich (7) adsorption isotherms [10, 11] were considered by following two equations below: 1 m L m C C q q K q (6) Log q = log KF + 1 FN log C (7) Where, C is Ni 2+ concentration in solution after adsorption, q is adsorption capacity, KL is Langmuir isotherm constant (L/mg), qm is maximum adsorption capacity (mg/g), KF (m/g) and NF are Freundlich isotherm parameters. 3. RESULTS AND DISCUSSION 3.1. SEM image The SEM image on figure 1 showed that MTT- PANi composite had morphology structure in short nanofibre form with diameter of 30÷50 nm, where PANi was continuous phase and MTT was dispersion one. Figure 1: SEM image of MTT-PANi composite 3.2. IR-spectrum 0.00 0.02 0.04 0.06 0.08 0.10 500 1000 1500 2000 2500 3000 3500 4000 In te n si ty c o ef fi ci en t ( a. u .) Wavenumber (cm -1 ) 1 6 9 6 .4 4 3 0 7 9 .4 7 3 1 2 7 .6 6 3 4 4 0 .0 8 2 9 4 2 .6 9 1 6 5 1 .4 6 2 8 6 1 .8 6 1 1 0 0 .5 0 1 3 0 7 .3 9 1 4 9 8 .5 4 1 5 8 8 .4 9 7 1 1 .4 5 1 0 3 7 .5 3 1 1 6 1 .2 2 6 1 7 .0 0 8 2 3 .8 9 5 4 2 .7 9 3 5 5 1 .9 9 3 3 5 3 .0 3 3 1 9 1 .3 8 (a) 0.00 0.02 0.04 0.06 0.08 0.10 500 1000 1500 2000 2500 3000 3500 4000 In te n si ty c o ef fi ci en t (a .u .) Wavenumber (cm -1 ) 3 1 8 7 .0 8 3 1 2 3 0 .8 4 3 4 4 9 .6 0 2 9 1 2 .0 6 1 7 2 9 .0 5 3 0 1 2 .0 7 1 0 4 3 .4 2 1 5 0 9 .3 6 1 6 4 6 .9 6 1 7 0 5 .7 3 6 0 4 .0 3 9 9 9 .4 3 1 1 6 1 .7 1 7 3 4 .4 0 8 3 3 .3 8 6 6 9 .2 2 3 5 4 9 .6 1 3 3 6 8 .3 6 3 3 0 5 .8 4 0.12 1 3 3 0 .7 1 3 0 9 3 .3 3 5 5 0 .9 2 1 4 2 4 .8 6 (b) Figure 2: IR-spectrum of MTT-PANi composite (a) and MTT (b) The data given in figure 2a showed that PANi coexisted in composite matrix because of the clear VJC, 54(4) 2016 Removal of Ni 2+ from aqueous solution by 431 presence of benzenoid and quinoid ring vibrations at 1558 cm -1 and 1498 cm -1 , respectively. Additionally, other main groups simultaneously appear in the IR- spectrum such as the band from 3551 cm -1 to 3191 cm -1 assigning to the N-H stretching mode, from 3079 cm -1 to 2861 cm -1 (aromatic C-H), from 1307 cm -1 to 1037 cm -1 (-N=quinoid=N-). The signals at 1696 cm -1 and 1651 cm -1 assign to C=O belonging to carbonyl group due to MTT. 3.3. Effect of pH The results presented in figure 3 showed that the adsorption of Ni 2+ ion rose unlinear with increase of pH of solution. In strong acid medium (pH < 3) the removal efficiency of Ni 2+ ion is very poor, but, it was better when pH over 4, among them the optimal pH of 6 could be used for continuous experiments. 0 20 40 60 80 100 0 1 2 3 4 5 6 7 8 pH H (% ) Figure 3: The effect of pH on the Ni 2+ ion removal efficiency of MTT-PANi composite (C0 = 1 mg/L; t = 40 min) It can be explained that at low pH medium, PANi can not function as a ligand or chelating agent because of its acid doped state (-N groups are protonated), therefore, the metal uptake is not occurred [8]. Conversely, in high pH medium, it existed in undoped form, then its free amine or imine groups will be available for metal chelating resulting in significant increase of Ni 2+ adsorption. 3.4. Effects of contact time and adsorption kinetics model The figure 4 indicated that the adsorption capacity of Ni 2+ ion onto MTT-PANi depended strongly on contact time t. It rose with increasing t during the first 40 initial minutes. After 40 min of contact time, the adsorption capacity changed insignificantly indicating that the equilibrium was obtained. The adsorption rates and correlation coefficients (R 2 ) given in Table 1 resulted from figures 5 showed that the values of R 2 for the first order adsorption kinetic model (0.3997) are less than that for the second one (0.9976). 0 4 8 12 0 20 40 60 80 100 t (min) q t ( m g /g ) Figure 4: Plot of adsorption capacity versus time for initial Ni 2+ concentration of 1 mg/L at pH = 6 There was a larger difference for qe between the experimental (11.4666 mg/g) and calculated (1.5431 mg/g) values belonged to the first – order kinetic model. It explained that the adsorption process of Ni 2+ onto regarded adsorbent did not follow the first- order kinetic model. Conversely, the calculated qe value from the second-order equation (11.51 mg/g) agreed very well with the experimental one (11.4666 mg/g) indicated that the mechanism of the adsorption of Ni 2+ ion onto MTT-PANi was followed by pseudo second – order kinetic. y = -0.0063x + 0.1884 R 2 = 0.3997 t (min) -0.4 lo g ( q e- q t) -0.2 0.0 0.2 0.4 0 10 20 30 40 50 60 70 80 90 y = 0.0869x + 0.2315 R 2 = 0.9976 0 2 4 6 8 10 0 20 40 60 80 100 120 t (min) t/ q t ( m in .g /m g ) (b) Figure 5: The first-order (a) and second-order (b) adsorption kinetic models of Ni 2+ ion onto MTT-PANi composite (C0 = 1 mg/L) VJC, 54(4) 2016 Phan Thi Binh, et al. 432 Table: Kinetic parameters for adsorption of Ni 2+ onto MTT-PANi composite C0 (mg/L) Experimental value qe (mg/g) First-order adsorption kinetic model Second - order adsorption kinetic model y = -0.0063x + 0.1884 y = 0.0869x + 0.2315 qe (mg/g) k1 (min -1 ) R 2 qe (mg/g) k2 (g/mg.min) R 2 1 11.4666 1.5431 0.0145 0.3997 11.51 0.033 0.9976 3.5. Effect of initial Ni 2+ concentration Figure 6 showed the effect of varying concentration on Ni 2+ adsorption ability of MTT- PANi within 40 min contact time at pH of 6. It was found an efficiency of Ni + removal about near 60 % which was insignificantly different in research concentration of Ni 2+ from 0.338 to 2.235 mg/L. 0 20 40 60 80 100 0.0 0.5 1.0 1.5 2.0 2.5 C0 (mg/l) H ( % ) Figure 6: The influence of initial concentration on Ni 2+ removal efficiency 3.6. Adsorption isotherms The Langmuir dimensionless parameter can be calculated from equation (8): 0 1 1 L L R K C (8) Where KL is Langmuir constant and C0 is initial concentration of Ni 2+ . Table 2: Values of dimensionless Langmuir parameter RL for Ni 2+ ion adsorption C0 (mg/L) 0.338 0.798 1.845 2.115 2.235 RL 0.9287 0.8466 0.7047 0.6755 0.6633 Table 3: Langmuir and Freundlich adsorption isotherm constants for Ni 2+ onto MTT-PANi Langmuir constants Freundlich constants qmax (mg/g) 66.6700 qmax (mg/g) 66.6700 KL (L/mg) 0.2271 KL (L/mg) 0.2271 R 2 0.6764 R 2 0.6764 y = 0.0154x + 0.0554 R 2 = 0.6764 0.00 0.02 0.04 0.06 0.08 0.0 0.2 0.4 0.6 0.8 1.0 1.2 C (mg/l) C /q ( g/ l) (a) y = 0.8934x + 1.1544 R 2 = 0.9898 0.0 0.4 0.8 1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 log C lo g q (b) Figure 7: Langmuir plot (a) and Freundlich plot (b) for the adsorption of Ni 2+ onto MTT-PANi The obtained RL (table 2) and NF (table 3) values indicated that the adsorption process of Ni 2+ ion was favorable because of 0 < RL < 1 and 1 < NF < 10 [5]. The data given on Table 3 obtained from figure 7 explained that this fitted into Freundlich isotherm model more suitable than into Langmuir one because of higher R 2 (0.9898). NF The maximum adsorption capacity of Ni 2+ ion was found 66.67 mg/g by Langmuir isotherm line, while KF from Freundlich one was 14.269 mg/g. 4. CONCLUSION Nanocomposite based on Maize tree-trunk and polyaniline was successfully synthesized by chemical method. It could be useful for the removal of Ni 2+ ion from aqueous solution. The optimum conditions for Ni 2+ removal were found at pH of 6 and equilibrium contact time of 40 min. The adsorption of Ni 2+ onto MTT-PANi fitted into the VJC, 54(4) 2016 Removal of Ni 2+ from aqueous solution by 433 pseudo-second order kinetic model and followed the Freundlich adsorption isotherm equation. The maximum adsorption capacity (qmax) and Langmuir constant (KF) were 66.67 mg/g and 14.269 mg/g for Ni 2+ adsorption onto MTT-PANi, respectively. Acknowledgement. This study was financially supported by Institute of Chemistry under code number VHH.2016.1.03. REFERENCES 1. Sandeep Yadav, Varsha Srivastava, Sushmita Banerjee, Fethiye Gode, Yogesh C. Sharma. Studies on the removal of nickel from aqueous solutions using modified riverbed sand, Environ. Sci. Pollut. Res.. (2012) doi: 10.1007/s11356-012-0892-2. 1. M. G. Bhagyalakshmi and P. N. Sarma. Removal of Ni (II) from aqueous solutions using Sugarcane bagasse, Journal of Chemical and Pharmaceutical Research, 7(2), 140-147 (2015). 2. N. M. Salem, A. M. Awwad. Biosorption of Ni(II) from electroplating wastewater by modified (Eriolbotrya japocica) loquat bark. J. Saudi Chemical Society (2011) doi: 10.1016/j.jscs.2011.07.008. R. Ramya, P. Saukar, S. Anbalagan Sudha. Adsorption of Cu(II) and Ni(II) ions from metal solution using crosslinked chitosan-g-acrylonitrile copolymer, International Journal of Environmental Sciences, 1(6), 1323-1338 (2011). 3. M. Ghorbani, H. Eisazadeh and A. A. Ghoreyshi. Removal of zinc ions from aqueous solution using polyaniline nanocomposite coated on rice husk, Iranica Journal of Energy & Environment, 3(1), 83-88 (2012). 4. D. Liu, D. Sun and Y. Li. Removal of Cu (II) and Cd (II) From Aqueous Solutions by Polyaniline on Sawdust, Separation Science and Technology, 46(2), 321-329 (2011). 5. Phan Thi Binh, Pham Thi Tot, Mai Thi Thanh Thuy, Mai Thi Xuan, Tran Hai Yen. Regeneration of some adsorbents based on PANi and agriculture waste for removal cadmium(II) from solution, Vietnam Journal of Chemistry, 51(5A), 172-176 (2013). 6. R. Ansari, F. Raofie. Removal of lead ions from aqueous solution using sawdust coated by polyaniline, E–Journal of Chemistry, 3(1), 49-59 (2006). 7. Y. S. Ho, C. C. Wang. Pseudo-isotherms for the sorption of cadmium ion onto tree fern, Process biochemistry, 39, 759-763 (2004). 8. I. Langmuir. The constitution and fundamental properties of solids and liquids. Part I. Solids, Am. J. Chem. Soc., 38(11), 2221-2295 (1916). 9. H. M. F. Freundlich. Über die Adsorption in Lösungen Zeitschrift für Physikalische Chemie (Leipzig), 57A, 385-470 (1906). Corresponding author: Phan Thi Binh Institute of Chemistry Vietnam Academy of Science and Technology 18, Hoang Quoc Viet, Cau Giay, Hanoi E-mail: phanthibinh@ich.vast.vn.