Sarwar K*, Nadeem R, Fatima A, Nasar S, Subhan S and Atique M
Department of Chemistry, University of Agriculture, Faisalabad, Pakistan
Received Date: October 04, 2016; Accepted Date: October 24, 2016; Published Date: October 28, 2016
Citation: Sarwar K, Nadeem R, Fatima A, Nasar S, Subhan S, et al. (2016) Biosorption of Co(II) Metal by Original and KMnO4 Pretreated Trapa natan Biopolymer. Chem Sci J 7:141. doi: 10.4172/2150-3494.1000141
Copyright: © 2016 Sarwar K, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Bioadsorption of Co(II) metal ions from the aqueous medium using Trapa natan peels biomass was examined for preliminary pH, initial metal absorption and contact time. Pretreatment of biomass were carried out with oxidizing agents. The maximum uptake q (mgg-1) for Co(II) obtained by KMnO4 -TNP was about (53.92) as compared to Native- TNP (24.28) at pH 5. The equilibrium and kinetics models were applied over data. The Langmuir and Freundlich equilibrium adsorption models were investigated and observed to the fit the data. The Freundlich model gave better fit than the Langmuir model with R2 value of 0.9951. Kinetic study revealed that adsorption was fast in first 60 minutes and equilibrium was achieved after 120 minutes for Co(II) metal. The suitability of a pseudo second order chemical reaction for the sorption of Co(II) onto this biosorbent was apparent. The results revealed that Trapa natans peels biomass is effective, potential and best beneficial biosorbent for removal of heavy metals.
Biosorption; Trapa natan peels; KMnO4; Co(II)
Heavy metals pollution arises from different sources in the result of industrial actions and scientific improvement but most commonly is due to purification of metals. Discharge of the Heavy metals in the water bodies because of Anthropogenic actions is most important water pollution source. Co, Zn, Cu, Ni, Pb, Hg, are frequently detected in engineering wastewaters, which instigate as of metal plating, mining activities, smelting, battery construct, tanneries, oil refining, smear manufacture, pesticides, dye manufacture, printing and picturesque industries, etc. . Heavy metals must be removed before discharge because unlike organic wastes, heavy metals are non-biodegradable and build up in gulp of air tissues, and responsible for various diseases and disorders . Cobalt is an odorless, steely-gray, shimmering, rigid metal. Everyone is unwrapping to the fundamentals to small levels of Cobalt in atmosphere, stream and foodstuff. 2 gdm³ of Cobalt in consumption water has been estimated. Cobalt has both advantageous and destructive special effects on physical condition. Important natural sources of Cobalt in the atmosphere are loam, grime and marine irrigate. The sensitive Co (II) poisoning cause dangerous health hazards in humans like asthma, failure of heart, harm to liver and thyroid .
Many physicochemical techniques have been urbanized in favor of the eradication of metals from wastewater, for example mining, ion exchange, chemical rainfall and crust intake partition process. Development of professional and inexpensive partition processes is therefore of tremendous significance. Adsorption is another established technique for the exclusion of heavy metals from wastewater . Biosorption is the potential of dynamic sites on the shell of biomaterials to connect and deliberate heavy metals from even the most adulterate aqueous solutions. . The effectiveness of biomass be determined by on factors such as no. of sites on the biosorbent matter, their ease of access and chemical state such that the availability and the resemblance between sites and metal . The largest advantage of biosorption are the low working rate, chemical’s capacity to be minimized and disposal of organic slush and many competence in detoxifying very thin effluents .
Physical pretreatment method such as heat, autoclaving, glacial, ventilation and baking and substance pretreatment by means of alkali and organic chemicals showed improvement and diminution in metal bioadsorption,  Trapa natans fruit belonging to the family Trapaceae, its root is fine long and many in number, leaves are triangular, fan shaped. Trapa natans are nut like and one to two inches in diameter. The species are floating annual aquatic plant, growing in slow moving water up to 5 meters deep. The dried peels of Trapa natans are used in bleeding disorders, threatened abortion, dysuria, polyuria and oedema. The purpose of this stuff will be conclude the effect of element pretreatment for heavy metals elimination from biomass and to charge the changes in the uptake capacity of metals weather decrease or increase after the pretreatments.
The research work reported in this text was performed in the Research laboratory of Department of Chemistry, University of Agriculture Faisalabad, Pakistan. The research was carried out during 2013 to observe the biosrption of heavy metals from the aqueous solutions by waterchest nuts (Trapa natans. L) peels as biosorbent. All the samples of Trapa natans L. used were collected from Jhung bazaar of Faisalabad. This sampling area does not have any aforementioned history of contamination by heavy metals.
Preparation of biosorbents
Peels of Trapa natans L. were boiled in hot boiling water to made lenience to remove its peels, that are the biosorbent material then peels were washed with water to remove dust, cut into small pieces and first sun dried and then oven dried at 65°C for 48 hours. Dried biomass was ground and screened using Octagon Siever (OCT- DIGITAL 4527-01); uniform particle size fraction of 0.25 mm was obtained and stored in air tight container.
Pretreatment of biosorbents
Prior to use sample was pretreated with the Oxidizing Agents (KMnO4, H2O2 and K2Cr2O7) in the following way:
a) 10 g of biosorbent having particle size 0.25 mm was taken in conical flask and in it added 100 mL of 0.1M solution of KMnO4.
b) 10 g of biosorbent having particle size 0.25 mm was taken in conical flask and in it added 100 mL of 0.1M solution of K2Cr2O7.
c) 10 g of biosorbent having particle size 0.25 mm was taken in conical flask and in it added 100 mL of 0.1M solution of H2O2 and kept these three flasks in the shaker for constant shaking for 24 hours.
Samples were filtered, filtrate was useless and discarded. Extensive washing of biosorbent with distilled water was carried out to remove any unreacted chemical .
Preparations of metals solutions
The Co (II) stock solution having concentration 1000 mg/L was prepared by dissolving 4.15 g of cobalt chloride powder in 1000 mL of distilled water. Co (II) stock solution then prepared was immediately stored in airtight plastic bottles. From these stock solutions, solutions of different concentrations were prepared to be used in biosorption studies.
The amount of Co (II) taken up by biomass in each flask was calculated using following mass balance equation (Eq. 1) . The percentage removal was determined by equation 2.
Where “Ci (mg L-1)” and “Ce (mg L-1)” are the initial and equilibrium metal concentrations (mg L-1), respectively, qe (mgg-1) is the equilibrium sorption.
Batch biosorption studies
All glassware used for experimental purpose was washed with 60% (v/v) nitric acid and subsequently rinsed with DW to remove any possible interference by other metals. Biomass concentrations (0.1 g per 100 mL), biosorbent particle size (0.250 mm), contact time (24 h), temperature (30°C), shaking speed (150-200 rpm) to check the possible maximum removal of metal ions. Control assay was accompanied with each experiment. At the end of each experiment, flasks were removed from the shaker and solutions were separated from the biomass by filtration through filter paper.
Samples were filtered to remove solid particles and then were analyzed to determine the ion concentration by an atomic absorption spectrophotometer (Model: AAnalyst 300, Perkin–Elmer). Co(II) uptake was calculated by simple concentration difference method. Uptake of Co(II) was calculated from the mass balance equation.
where V is the volume of the solution (L),
Ci is the initial concentration (mg/L),
Ce is the final concentration in solution (mg/L) and m is mass of the sorbent (g).
% sorption is given as
% sorption=Ci–Ce/Ci × 100
Mean and standard error values were calculated from triplicate sets of experiments. All statistical analysis was performed using Microsoft Excel 2007, Version office XP.
In this research work, dried biomass of Trapa natans peels was used by the side of with pretreated biomass. The principle of inventive biomass of Trapa natans peels were to know its biosorption capability and then evaluate with the adsorption capacity of chemically pretreated biomass.
Effect of pretreatment
Comparing the results of pretreatments on Trapa natans peels 100 mgL-1 of Co (II) solutions were shaken at 200 rpm with 0.1 gm of pretreated Trapa natans peels. The particle size of the biomass was 0.25 mm at the pH of 5 for Co (II). One can notice that the pretreatment of biomass by KMnO4, K2Cr2O7 and H2O2 increased the sorption capacity (mgg-1) of biomass in order:
For Co(II) Nat-TNP (24.28)<H2O2-TNP (33.32)<K2Cr2O7-TNP (39.022)<KMnO4-TNP (53.92)
Generally, oxidizing agents treatment has been used for metal removal causing increase in sorption capacity. KMnO4 treatment showed remarkable increase in sorption capacity of biomass. KMnO4 pretreated biomass showed more sorption capacity and it was due to solubility of more mineral matter of biomass which resulted more porosity in biomass. According to this property it is also used in sterilizing wells of drinking water.
Chemical mechanism of KMnO4 pretreated TNP for adsorption
Adsorption mechanisms: Result from KMnO4 pretreated biomass suggesting that the precipitation was not an important mechanism for Co(II) removal. Compared with Native biomass, the amount of oxygen containing groups such as hydroxyl groups, phenolic hydroxyl and carboxyl functional groups increased significantly on the surface of the biomass after the KMnO4 pretreatment of the TNP. In addition, the pretreated biomass surface was also covered with ultrafine manganese oxide (MnO2 /Mn3O4) particles. In this work, both the functional groups and the MnO particles could serve as the main adsorption sites for heavy metal ions in aqueous solutions. As a result, the KMnO4 treated biomass showed much stronger binding affinity to the three heavy metal ions than native biomass particles.
Effect of pH
The outcome of pH on the elimination of Co (II) from aqueous solution by Trapa natans peels was studied by varying the pH (1-7) values while the other operational parameters were kept constant. Results of present investigation showed that sorption capacities (mgg-1) enlarged with growing pH from 1 to 7 for both metals. The absorption capacity (mgg-1) of Co (II) increased from 19.2 to 29.02, 27.7 to 39.1, 29.33 to 49.93 and 39.02 to 59.67 for Nat-TNP, H2O2-TNP, K2Cr2O7- TNP, and KMnO4-TNP when pH values of the solutions changed from 1 to 7. The results revealed that KMnO4-TNP possessed maximum biosorption capacity of 53.92 for Co (II) at pH value 5. Lower or high pH has resulted either in low biosorption or precipitation of the corresponding metal ions . The segregation of metal ions from distilled water solution by adsorption depended on the pH of solution, as the latter affected the surface charge of biosorbent, solution chemistry of metals, activity of functional group in the biomass, the degree of ionization and the species of adsorbate . Due to high proton focus at small pH, there is a decrease in metal ion biosorption. It is due to the positive charge accumulation on metal binding sites, hence protons struggle efficiently with metal ions for their binding. The cell surface of the biosorbent become more negative with rising pH due to deprotonation. Due to this more metal ions were attached with active sites. The positively charged ions of the metals then race more affectively for existing binding sites, which increased the sorption . The selection of the optimum pH must take into account for proper sorption of the metal ions. At optimum pH value (pH 5 for Co (II) metal) the surface of the Trapa natans peels is negatively charged due to the dissociation of the COOH groups . Related results have been accounted in literature by  in his study of Utilization of Blighia sapida (Akee apple) pod in the removal of Pb (II), Cd (II) and Co (II) ions from aqueous solution.
Effect of initial metal concentration
The above-mentioned effect on the deletion of Co (II) from the aqueous solutions by Trapa natans L. peels in its native as well as pretreated form were studied at pH 5.0 by changing the amount of the system from 25 to 400 mgL-1 . Results showed that biosorption power increased with increased in initial metal ion concentration of Co (II) on the biomass and %age removal decreased with increased in initial metal concentration. The Figures 1-3 shows that sorption capacities (mgg-1) in case of Co (II) increased from 9.33 to 80, 16.21 to 122.1, 19.33 to 149.50 and 21.07 to 204.4 while % removal decreased from 37.32 to 20, 64.84 to 31.52, 77.32 to 37.37 and 84.28 to 51.1 for Nat-TNP, H2O2- TNP, K2Cr2O7-TNP and KMnO4-TNP as concentration increased from 25 to 400 mgL-1 . The maximum uptake q (mgg-1) obtained by biomass TNP was (204.4) for Co (II) with KMnO4-TNP in contrast with native- TNP at 400 mgL-1 . The concentration of metal ions present initially is an important factor here. It offers a vital energetic force to prevail over all mass shift confrontation of metal ions between the its solution form and pure solid form, for this reason, the elevated the early focus of metal ions, the more the adsorption capacity and decrease the percentage adsorption of dried biomass. Biosorbents show a controlled number of dynamic sites and at a certain concentration these become occupied . Adsorption isotherms of Co (II) concentration from 25 to 400 mgL-1 at pH 5.0 were studied keeping a permanent adsorbent dose (0.1 g/100 mL).
Adsorption isotherms of Co (II) concentration from 25 to 400 mgL-1 with a fixed adsorbent dose (0.1 g/100 mL) at pH 5 was studied. Freundlich and Langmuir adsorption isotherms were applied to describe the equilibrium relationships between sorbent and sorbate in solution. Sorption equilibrium is established when the concentration of sorbate in the bulk solution is dynamic balance with that of the interface . To get the equilibrium data, initial concentration of Co (II) were varied while the weight of biomass was kept constant. Twentyfour hours of equilibrium period for sorption experiments were used to ensure equilibrium conditions.
The general form of Langmuir isotherm equation is written as:
According to this model, all adsorbed species interact only with a site and not with each other and the adsorption is limited to monolayer. It is then assumed that once a metal ion occupies a site, no further sorption can take place. A monolayer was formed when the equilibrium was attained. The linearized form of Langmuir isotherm equation is written as:
By using the Linearized Langmuir equation Langmuir parameters were calculated.
Langmuir isotherms are presented in Figure 2 for Co (II) which is plots of Ce/Qe gL-1 verses Ce mgL-1 under different concentrations of metals. Straight lines with R2 values as shown in Table 1, 0.943, 0.976, 0.993 and 0.999 for Co (II) sorption by Nat-TNP, H2O2-TNP, K2Cr2O7-TNP and KMnO4-TNP were obtained. Linearization of graph and theoretical monolayer capacity (qmax) calculated for Co (II) on the Nat-TNP, H2O2-TNP, K2Cr2O7-TNP and KMnO4-TNP found to be agreeing with the experimentally determined sorption.
Table 1: Comparison of Langmuir and Freundlich isotherm parameters of Co (II) biosorption by Trapa natans peels.
The general form of Freundlich isotherm equation is written as:
The Freundlich isotherm equation assumes that a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interaction between adsorbed molecules. The linearized form of Freundlich isotherm equation is written as:
The linear plot of the Freundlich isotherm model for sorption of Co (II) is presented in Figure 3 for Co (II). From Table 1, R2 values with respect to the sorption of Co(II) for Freundlich isotherm model was noted to be 0.913, 0.687, 0.693 and 0.761 Nat-TNP, H2O2-TNP, K2Cr2O7-TNP and KMnO4-TNP respectively, these values are greater than R2 values obtained in case of Langmuir model.
Effect of contact time
For the sorption mechanism of Co (II) metal cation onto Nat-TNP, KMnO4-TNP, K2Cr2O7-TNP and H2O2-TNP, a kinetic investigation with different time intervals ranging from 0 to 1440 minutes (0, 15, 30, 60, 120, 180, 240, 360, 480, 720, 960 and 1440) was conducted having metals concentration 100 mgL-1 . In order to determine the contact time taken to reach the equilibrium and to study the effect of the sorbent particle size. It can be seen that the cobalt (II) removal increase rapidly with the contact time up to 15 min and reached maximum at 1440 minutes. For Co (II), uptake capacity (mgg-1) increased from 12.21 to 24.28, 13.67 to 33.32, 17.17 to 39.03 and 21.89 to 53.92 for Nat-TNP, H2O2-TNP, K2Cr2O7-TNP and KMnO4-TNP as time increases from 0 to 1440 minutes. The maximum uptakes (mgg-1) obtained by TNP was (53.92) for Co (II) with KMnO4-TNP in contrast with native at 1440 minutes. The initial sorption rate was quick and can be explained on the fact that the metal ions interact easily with the adsorption sites which are open and extra cellular binding takes place causing adsorption rate to become high. During the first few minutes, adsorption rate was extremely sharp then the rate began to drop toward a steady state and reached maximum at 1440 minutes with insignificant levels of adsorption . There are two basic reasons to account for the slow sorption stage. According to the first reason sluggish sorption was resulted by intracellular binding and per the second it was due to slower distribution of solute particles into the core of the adsorbent (biomass) .
In order to examine the mechanism of kinetics of Co(II) adsorption and rate controlling step, two kinetic models, Lagergren’s pseudo 1st order and pseudo 2nd order were fitted to data . The Pseudo 1st order Lagergren model for solid/liquid systems of adsorption is express as:
It is clear from Figure 4 that the pseudo 1st order kinetic equation fails to predict the experimental adsorption capacity (qexp) because R2 values of pseudo 1st order kinetics are relatively lower then pseudo 2nd order kinetics. From Table 2, the results cleared that qe mgg-1 (0.587, 0.809, 0.220 and -0.069) for Co(II) sorption values with Nat-TNP, H2O2-TNP, K2Cr2O7-TNP and KMnO4-TNP respectively estimated from the pseudo 1st order kinetic model was found not to be agreeing with the qexp (experimental capacity).
|MetalIons||Biosorbent||Pseudo first order||Experimental
|Pseudo second order|
Table 2: Comparison between Lagergren pseudo-first-order and second-order kinetic models for the biosorption of Co (II) using Trapa natans L peel.
Pseudo 2nd order equation
Adsorption kinetic data was more analyzed by using pseudo 2nd order kinetics model. It is express as:
k2 is known as the equilibrium rate constant of pseudo 2nd order biosorption (gmg−1min−1). To calculate the pseudo 2nd order rate constants k2 and qe intercept and slope of the plot t/q versus t were used.
While pseudo 2nd order kinetic model qe mgg-1 (12.65, 20.20, 35.21 and 59.52) was found to be agreeing with the qexp (experimental capacity) (24.28, 33.32, 39.03 and 53.92) for Co(II) sorption values. This confirmed that pseudo 1st order kinetic model is not accurate for sorption kinetics of Co(II) sorption by Nat-TNP, H2O2-TNP, K2Cr2O7- TNP and KMnO4-TNP. Both facts suggested that the adsorption of Co(II) ions follow the 2nd order kinetics model, as shown in Figures 5-8 which depends on the hypothesis that adsorption may be a rate limiting step. During the study of contact time, initial concentration, equilibrium concentration and contact time were used as an experiment variables [18,19].
Even though the technology also suffers inherent disadvantages like early saturation of biomass, little biological control over the characteristics of biosorbents. It offers several advantages, including cost effectiveness, high efficiency, minimization of chemical/ biological sludge, and regeneration of biosorbent with possibility of metal recovery. In countries, with the rush for rapid industrial development coupled with lack of awareness about metal toxicity, there is an urgent need for developing an economical and eco-friendly technology which satisfies these demands where other conventional methods fail. These findings demonstrated that Trapa natans L. is cost effective, potential and a novel biosorbent for the removal of heavy metals such as Co (II) from the aqueous solution. The pretreatment method thus can be used to prepare high-efficiency biomass for heavy metal remediation.