Synthesis, Characterization and Adsorption Study of Composite

ISSN: 2278 – 7798 International Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, May 2016

Synthesis, Characterization and Adsorption Study of Composite Adsorbent using Corncob and Cornstarch Shekhar L. Pandharipande, Grishma A. Borkar

 Abstract—Agricultural waste contains carbon in significant proportions. The commercial grade activated carbon being a very effective adsorbent, the prime focus of the present work was on its synthesis using agro-based waste corncob. It also addressed the pelletization of the adsorbent powder synthesized from corncob and further making its composite using corn starch as binder. The BET surface area of the composite adsorbent pellet (CA) was found to be 17% more than that of the corncob activated carbon (CCA). The SEM images have indicated that the CCA synthesized has irregular porous structure and the CA had homogeneous bands with active sites. The adsorption studies showed that CA showed a maximum 77% adsorption for initial concentration of the 10 ppm solution of methyl violet in aqueous solution whereas the CCA showed a maximum of 63%. The novel feature of the present work was on pelletization of adsorbent powder which could ease the handling, separation and storage difficulties.

huge cost and its regeneration problem. However this problem can be solved by using adsorbents made from agricultural by-products and waste materials. The different types of agro-based waste materials that are being developed as adsorbents are coconut shell, almond shell, peanut shells, coir pith, chestnut, mango leaves, banana leaves, papaya leaves, spent tea leaves, etc. Adsorbents which are made from two or more materials are termed as composite adsorbents. The process in which these composite adsorbents are being used is known as composite adsorption. Composite adsorbents are made to increase the efficiency of the process which cannot be achieved by using single adsorbent material. Hence, composite adsorbents have a potential in applications in many fields when compared with the use of single adsorbent. The objective of the present work is to utilize the agro-based waste material corncob with cornstarch to synthesize composite adsorbent. II. LITERATURE REVIEW

Keywords: agro-based waste, composite adsorbent, corncob activated carbon, pelletization.

I. INTRODUCTION Use of dyes in order to color variety of products is increasing year after year. This is resulting in generation of considerable amount of colored wastewater. Usually it can be noted that public‟s understanding of water quality is highly influenced by its physical appearance i.e. its color. The dyes which are responsible for the color are many times toxic and even carcinogenic, which pose a danger to the aquatic living organisms as well as human beings. Various methods are being employed for decolorization, but among them adsorption is the method of choice and gives the best results. There are various commercial adsorbents such as activated carbon, silica gel, zeolite, etc. Out of these activated carbon are highly effective in the removal of dye from wastewater. The only disadvantage of the commercial adsorbent is its Manuscript received April, 2016. Shekhar L. Pandharipande, Department of Chemical Engineering, Associate Professor, Laxminarayan Institute of Technology, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India, +91-9823360705 Grishma A Borkar, Department of Chemical Engineering, Student, Laxminarayan Institute of Technology, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India, +91-8600298801.

A number of research papers have been published on the topic of synthesis of activated carbon from agro-based waste materials. Few are cited here; a. Paper titled “Porous structure and surface chemistry of phosphoric acid activated carbon from corncob”, reports a series of activated carbons prepared from agricultural waste corncob by chemical activation with phosphoric acid at 400ºC using varied ratios of impregnation. It shows that carbons are highly porous (BET surface area 2081 m2/g, total pore volume 1.13 cm3/g) and contain large amount of acid surface groups (3.73 mmol/g). b. The paper titled “Preparation of activated carbons from corncob with large specific surface area by a variety of chemical activators and their application in gas storage”, reports that activated carbons were produced from corncob using different activation strategies and activators as reported in the paper titled. All carbons show microporous character, except for the sample that is activated by one-step phosphorous acid activation which shows hysteresis typical of mesoporous character. c. The paper titled “Adsorption of cadmium(II) from aqueous solution on natural and oxidized corncob” showed that Ca-treated corn cobs powder is effective as an adsorbent compared to Al-treated corn cobs powder. The natural and corncob oxidized with CA and NA since they possess a greater amount of acid sites than basic ones. The PZC of

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ISSN: 2278 – 7798 International Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, May 2016 these three adsorbents were 6.2, 2.9 and 3.3, respectively, indicating that their surfaces are of acidic nature. d. The special feature of the paper titled “Synthesis of Adsorbents From Waste Materials Such As Ziziphus Jujube Seed & Mango Kernel” is to utilise the commonly available waste materials such as mango kernel and seed of ziziphus jujube. In their work these materials have been converted into the activated carbon with thermal treatment & is further utilised for the adsorption of colour from the aqueous solution of methyl red. e. The paper titled “Textile Dye Removal Using Pelletized Agro waste”, reported that, three pelletized biosorbents were effective for the removal of methylene blue dye as reported in the paper titled. It was found that the adsorption capacity of guava leaves pellets was superior due to the presence of various surface functional groups. III. PRESENT WORK The objective of the present work is to utilize corncob, a waste from agricultural fields into useful product such as an adsorbent. It is further extended in synthesis of composite adsorbent with corn starch to form pellets. The effectiveness of composite adsorbent is tested in removal of dye methyl violet; from aqueous solution. Chemical as well as thermal treatment are employed in synthesis of adsorbent. The work was divided into four parts: 1. Synthesis of Corncob Adsorbent (CCA) 2. Synthesis of Composite Adsorbent (CA) using CCA and Corn Starch (CS) 3. Characterization of the composite adsorbent 4. Adsorption Studies The methodology adopted in present work is shown in Fig. 1 whereas the pictorial representation is shown in Fig. 2:

A. SYNTHESIS OF ACTIVATED CARBON 1. Waste corncob were collected, washed to remove dust and cut into small pieces. The cut piece material was solar dried for three days and grounded into fine powder and sieved. 2. The powder was oven dried at 110º C for 1 hr for removal of moisture content remained. 3. The 1 gram of dried powder was chemically treated with 25 ml KOH solution having concentration of 1mol/l. The mixture was stirred for 2 hr at room temperature and kept overnight. 4. After the activation, all the samples were washed with water. This was continued until the pH value of the washing effluent reached approximately 7. The powder was separated by filtration. 5. The chemical treatment is followed by thermal treatment. The powder obtained was carbonized at 400° C for 1.5 hr. The adsorbent synthesized was further used in adsorption studies. B. SYNTHESIS OF COMPOSITE ADSORBENT Cornstarch was used as a composite material. Firstly, a gel solution of starch was prepared, CCA was mixed. The proportion of cornstarch was varied as 10%, 15%, 20% and 35%. The solution was dried on petridish for 24 hrs at room temperature to form small pellets which are stored in airtight bottles. C. CHARACTERIZATION Out of the 4 samples prepared, the sample with 35% cornstarch composition was observed to retain pellet form and is further used for the experimentation. 1. BET Surface Analysis: The BET surface area of the adsorbent CCA was found to be 187.92 m2/g and that of CA pellets was 224.13 m2/g. 2. SEM Morphology: The SEM analysis was conducted for CCA and CA. Figure 3.a and 3.b represents the SEM images for CCA and Figure 3.c, 3.d and 3.e represents for CA. It can be seen that the adsorbent CCA has irregular shape and porous structure. From the SEM image for CA, homogeneous bands are observed, which accounts for proper binding of CCA with CS.

Fig. 1: Methodology

Fig. 3.a


Fig. 2: Pictorial Representation of the Methodology

ISSN: 2278 – 7798 International Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, May 2016

Fig. 3.b

Fig. 3.c

Fig. 3.d

Fig. 3.e

Fig. 3: Scanning Electron Microscopy; For Adsorbent CCA: Fig. 3.a, 3.b; For Adsorbent CA: Fig 3.c, 3.d, 3.e

D. STANDARDIZATION OF COLORIMETER Colorimeter is used for analysis of adsorption study samples. The colorimeter was first standardized. The optical density of samples having known concentration of methyl violet was estimated using colorimeter .The graph between optical density and concentration is plotted as shown in Figure 4, which is used in estimation of concentration of methyl violet in aqueous solution obtained after adsorption by determining its optical density.

E. ADSORPTION STUDIES Known concentration and volume (20 ml each) of feed solution taken in a conical flask was added with 0.1 gram of each adsorbent respectively (i.e. CCA and CA). Four samples were prepared having concentration of 10 ppm, 20 ppm, 30 ppm and 40 ppm of methyl violet respectively. This solution was stirred for approximately 45 minutes. Two phases were separated and further analysis was done using a colorimeter. The concentration of methyl violet in solution separated after adsorption was decided by referring standardization curve. Calculations were done to determine the % adsorption and uptake of adsorbent (mg/g of adsorbent). IV. OBSERVATION AND CALCULATIONS The details of observations is given in Table I and the estimated concentration of solution obtained after adsorption is given in Table II after referring standardization curve.

Fig. 4 Standardization Graph


ISSN: 2278 – 7798 International Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, May 2016 Table I: Details of observation of adsorption studies Adsorbent

Quantity of Adsorbent (gram)

Concentration of original solution (ppm)

AC

0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

10 20 30 40 10 20 30 40 10 20 30 40

CS

CA

Optical density of original solution 0.18 0.36 0.56 0.70 0.18 0.36 0.56 0.70 0.18 0.36 0.56 0.70

Optical density of solution after adsorption 0.08 0.18 0.39 0.58 0.02 0.09 0.28 0.40 0.04 0.14 0.35 0.52

Table II: Concentration of solution after adsorption Adsorbent

Optical density of solution after adsorption

Concentration of solution after adsorption (ppm)

AC

0.08 0.18 0.35 0.52 0.02 0.09 0.28 0.40 0.04 0.14 0.39 0.58

3.6581 7.481 16.95 29.06 1.5114 4.026 11.692 17.475 2.216 5.911 14.946 24.58

CS

CA

Figure 5 shows the graph plotted between % adsorption and concentration of solution (ppm) for each adsorbent. Figures 6, 7 and 8 shows the graph plotted between uptake capacity (mg/g of adsorbent) and concentration of solution (ppm) for each adsorbent.

Fig. 5: % Adsorption vs Initial Concentration

Fig. 6: Uptake Capacity of CCA vs Initial Concentration

Fig. 7: Uptake Capacity of CS vs Initial Concentration

Fig. 8: Uptake Capacity of CA vs Initial Concentration


ISSN: 2278 – 7798 International Journal of Science, Engineering and Technology Research (IJSETR) Volume 5, Issue 5, May 2016 V. RESULTS AND DISCUSSIONS The BET surface area of commercial grade activated carbon ranges from 400- 1000 m2/g. The surface area of the CCA synthesizes in present work is187.92 m2/g and that of the pellets of CA is 224.13 m2/g. It was observed that the BET surface area of the composite adsorbent pellets was more than the powdered adsorbent. Figure 5 shows the dependence of the percentage adsorption on the initial concentration. It shows that the % adsorption is inversely proportional to the initial concentration of methyl violet for each adsorbent (Figure 5). The % adsorption of the pellets of CA is more than that of CCA. However, different from the percentage adsorption, with the increasing initial concentration of methyl violet from 10 ppm to 40 ppm, the amount adsorbed after 45 minutes of stirring increased (Figure 6, 7, 8). This may be due to increase in driving force of the concentration gradient to overcome all mass transfer resistance of methyl violet between aqueous and solid phases and improved contacting between the dye and sorbents, thus resulting in higher uptake of methyl violet. The maximum uptake capacity was of corn starch, as starch in itself is a very good adsorbent. CA showed high uptake capacity in comparison with CCA. VI. CONCLUSION Present work is aimed at preliminary studies in exploring the possibility of utilization of corncob as an adsorbent in removal methyl violet from aqueous solution. Chemical as well as thermal treatment was employed in synthesis of adsorbent. The main focus of the work was on synthesis of adsorbent pellets which could ease the handling, separation and storage difficulties. Based on observation, result and discussion it can be concluded that, the composite adsorbent synthesized in pellet form is successful having large surface area of 224.13 m2/g which is 17% more than the powder used in its synthesis. Also the pellets retained its strength in aqueous solution and has fairly large separation efficiency ranged between 38% to 77%. It can be concluded that activated carbon from corncob as an adsorbent has potential in removal of methyl violet. Utilization of abundant agricultural waste into useful product which can be effective in decolorization of colored industrial wastewater.

corncob; Separation and Purification Technology 45 (2005) 41–49. [4] S. L. Pandharipande et al.; 2012. Synthesis Of Adsorbents From Waste Materials Such As Ziziphus Jujube Seed & Mango Kernel; International Journal of Engineering Research and Applications (IJERA) ISSN,Vol. 2, pp.1337-1341 [5] Lekha K B et al.; 2014. Textile Dye Removal Using Pelletized Agro waste; IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT). [6] Grishma A. Borkar; B.Tech Major Project report titled “Synthesis and Study of Composite Adsorbent from Corncob”, Rashtrasant Tukadoji Maharaj Nagpur University Nagpur, Nagpur. AUTHORS Shekhar L. Pandharipande is working as associate professor in Chemical Engineering department of Laxminarayan Institute of Technology, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur. He did his master in 1985 & joined LIT as a Lecturer. He has coauthored three books titled „Process Calculations‟, „Principles of Distillation‟ & „Artificial Neural Network‟. He has two copyrights „elite-ANN‟ & „elite-GA‟ to his credit as coworker & has more than 60 papers published in journals of repute.

Grishma A. Borkar is a Final year B.Tech Student in Chemical Engineering Department of Laxminarayan Institute of Technology, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur.

ACKNOWLEDGMENT Authors are thankful to Director, L.I.T. Nagpur for constant encouragement and support. REFERENCES [1] Sycha. N. V. et al.; 2012. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob; Applied Surface Science 261 (2012) 75– 82 [2] Yong Sun et al.; Preparation of activated carbons from corncob with large specific surface area by a variety of chemical activators and their application in gas storage; Chemical Engineering Journal 162 (2010) 883–892 [3] R. Leyva-Ramos et al.; 2005. Adsorption of cadmium(II) from aqueous solution on natural and oxidized
