GRAFT COPOLYMERIZATION OF ACRYLAMIDE MONOMER ONTO RECYCLED CELLULOSE BACKBONE AND ITS EFFICACIES FOR REMOVAL OF SOME HEAVY METAL IONS IN WASTE WATER

Acrylamide was grafted onto cellulose backbone of old newspaper by CAN initiator in aqueous medium. Grafting parameter such as percentage grafting (GP%) and Grafting yield(GY%) was evaluated at different reaction conditions such as temperature, time, monomer and initiator concentration. Hence it was after 150 minutes (at Temperature of 50 C, 2.5 g of CAN, 4 g of AAM) had highest GP% of 97% and GY% of 160% for CE-g-PAAM respectively. The products were characterized by FTIR and TGA analyses. Removal of heavy metals from wastewater was evaluated using the grafted copolymer. The results revealed promising potential of the grafted cellulose as adsorbent for remediation of waste water.


INTRODUCTION
Significant advances in cellusolic modifications and the resultant production of derivatives with unique chemical and physical properties have dramatically increase interest in cellulose research over the past decade. Polymers comprise of both natural and synthetic materials with a wide range of properties which makes them very much essential in daily's life. Some of the naturally occurring polymers are proteins, starches, cellulose and latex. Cellulose is a polymer (macromolecule) which consists of repeating units of structure that are typically interconnected via covalent bonds. Cellulose comprises of large numbers of hydroxyl groups which are chained together linearly (Badawyet al. 2005). The availability of cellulose constitutes are most abundant worldwide and it's one of the renewable polymer resources as well. Although, annually 1011×10 12 ton of cellulose is being generated by photosynthesis in its pure form yet, commonly, cellulose merges with lignin and other hemicelluloses of woody plant's cell wall (Malaque et al., 2007) Copolymerization increases the physical components and the efficacy of a polymer for many applications. Copolymerization changes the structure of the polymer chain and modulates all intramolecular and intermolecular forces, Characteristics like crystallinity, temperature, glass transition, chemical reactivity, permeability and elasticity can be change within wide range (Chhatbar et al., 2009). Graft copolymer, are branch molecules where the key chain is made completely of one repeated unit, while the branch-chain are made of different another repeated unit (Crini et al. 2004). Hence, it is essential to modify the properties of polymers in order to align them to designed tailormade specification for target applications. Grafting is a simple technique used to incorporate desired active functional groups on the backbone of a polymer for different purposes. Grafting copolymerization onto cellulose induces physical changes, since the introduction of side chains leads to different structural characteristics in raw materials. Grafting of cellulose shows new properties such as hydrophobic or hydrophilic character and resistance to chemical and biological agents (Nada, 2010).

MATERIALS
All the glass wares used throughout the experiment were rinsed using fresh solution of HNO3/HCl (3:1, v/v) washed with distilled water and dried before used. Measuring cylinder, test tube, stainless sieve, conical flask, Ceric ammonium nitrate, Acrylamide, Sodium hydroxide and sodium hypochlorite were purchased from sigma Aldrich chemicals pvt. Ltd, sulfuric acid paraffin oil and Nitrogen gas were obtained from Umaru Musa Yar'adua University laboratory. GRAFT COPOLYMERIZATION 250 ml three-neck flasks equipped with a stirrer and condenser was used by immersing it into paraffin oil. N2 was purge into the flask to remove oxygen during the reaction. 5 g of cellulose was prepared was added into 100 ml distilled water and was preheated at 80°C for 30 min with stirring. The contents of the flask were cooled down to 50 0 C and then 2 ml of H2SO4:H2O (1:1) was added to the reaction mixture. The required amount of 0.1M CAN solution was added after 5 min., and the reaction mixture was stirred uniformly. The required amount of AAM monomer (1, 2, 3 and 4 g) after 10 min was added and stirred for 60 minutes throughout the process. At the end of the reaction, the product was cooled and poured into 200 ml of methanol/acetone to create precipitation. The grafted sample was washed several times with methanol/ H2O at the ratio of 4:1, and then dried in oven at 50°C to constant weight (Kaur et al., 2013) Grafting parameters such as monomer concentration, Initiator concentration, time, temperature were optimized using the procedure described above. The Grafting percentage (%GP) was calculated according to Fernandez et al., (1990).
3 Wi= final weight of grafted Cellulose, Wo= initial weight of cellulose before grafting and W2= is the weight of monomer

CHARACTERIZATION METHODS
The non-grafted cellulose and the grafted cellulose were characterized by Fourier transform infrared spectroscopy (FT-IR) and Thermogravimetric analysis (TGA). FTIR analysis was carried out using an 8400S Shimadzu Japan spectrometer, and TGA of the samples were analyzed for its thermal stability with Perkin Elmer

BATCH ADSORPTION EXPERIMENT (GENERAL PROCEDURE)
Adsorption experiments on CE-g-PAAM were carried out by batch adsorption method. Various Parameters such as contact time, adsorbent dosage and Temperature were studied at constant agitation rate of 200rpm. The adsorption measurements were conducted in 250cm 3 Elemental flask, containing 50 cm 3 wastewater samples. The solutions were agitated using an orbital shaker, to reach equilibrium which later, the sample was removed and the supernatant solutions was removed from the adsorbent by filtration using Whatman No. 41 Filter paper. The filtrates were analyzed using AAS. Thereby, the percentage adsorption was evaluated using equation 3.4 Where Co (mg/L) is early metal conc., Ce(mg/L) is the equilibrium conc., V stand for the volume of metal solution used and W(g) stand for the gram of the adsorbent used (Nada,2010) RESULTS AND DISCUSSION GRAFT COPOLYMERIZATION Cellulose obtained from old newspaper was grafted with polyacrylamide using CAN as an initiator. Various grades of graft copolymers were synthesized by optimizing various parameters such as the initiator (CAN) concentration, Monomer concentration, time and temperature. The results were presented in Table 1.  Monomer = 4 g, Time = 150min, and Wo=5 g The graft copolymerization was carried out at various reactions conditions. The highest percentage grafting GP% and percentage yield GY% were 97% and 160% respectively at 150mins (time), 50°C (temp.), 1.5g (CAN) and 3g (AAM) ( Table 1). The results also showed that as the monomer concentration increased there was an increased in %GP, reaching a maximum value of 52% at 3 g for PAAM. Thereafter, there was decrease in % GP with increase in PAAM concentration (Sharma et al., 2003, Gupta, 2002. The increase in GP% with the initial increase in PAAM concentration was resulted by the positive change in the rate of diffusion of the monomer into the cellulose backbone which provided more chances for graft copolymerization to occur and thereby the GP% increased. The enhancement in % GP by increasing monomer concentration to higher value could be due to the greater availability of monomer to grafting site (Salisu et al., 2015). Hence, the decreasing tendency of % GP and beyond higher monomer concentration could be as a result of the competition between homopolymerization and graft copolymerization, where the homopolymerization prevails over the graft copolymerization at higher PAAM concentration (Sharma et at., 2003) similar trends have been reported by other researchers. (Yong et al., 2005;Sadeghi et al., 2011). CHARACTERIZATION THERMOGRAVIMETRIC ANALYSIS TGA of CE and CE-g-PAAM was presented in Figure 1. It was observed that the TGA of CE and CE-g-PAAM shows a twostep weight decrease. The first weight decrease of almost 25.97 % (70 w %) at 300-400 o C was due to vaporization of moisture (Shah et al., 1994) and the second weight loss of about 70.37 % (30w %) in the range 400-500 0 C, this was resulted from the intricacy of the process, which led to the dilapidation of the sample, which leads to formation of H2O, Methane and release of Carbondioxide and N2 for CE-g-PAAM (Bagheri et al., 2009). the initial step of the weight decrease of almost 32.29 % (70 w %), started from 300 to 400 0 C, was due to the release of CH4 and H2O while the corresponding step of weight decrease of 91.57 % (10 w %) started at 500-600 0 C for CE. This might be as a result of breaking of cellulose chains and finally to change formation of the inorganic components. Hence these indicate that the graft copolymer has increased thermal stability as related to CE. A drastic weight loss was observed for ungrafted cellulose (CE) this may be due to decomposition of ungrafted cellulose in structural form. Another thermal stability  Had wave number starting from 650 to 4000 cm −1 . The absorption peak of 3400 cm −1 could be as a result of the presence of hydroxyl group stretching in the CE (El-hady and Ibrahim 2004). The peaks at 1026 cm −1 and 2983 cm −1 may be due to C-C and C-H stretching vibrations (Ibrahim et al., 2002) and the peaks at 896cm −1 may be due to stretch C1-O-C4 (Dhiman et al.,2008). In case of the CE-g-PAAM, additional absorption bands appeared at 3164 cm −1 and 1670 cm −1 . This could be attributed to Amide group stretching of the grafted chains and carbonyl group stretching (primary amide) and scissor vibrations in polyacrylamide, respectively (El-hady and Ibrahim 2004). The appearance of these bands successfully confirmed the grafting of old newspaper with acrylamide. The efficacy of CE-g-PAAM as adsorbent for the removal of metals ions (Fe 2+ , Pb 2+ and Cu 2+ ) from waste water was also determined using batch adsorption system. The initial concentration of Fe 2+ , Cu 2+ and Pb 2+ ions in waste water were 43.44ppm, 69.02ppm and 11.22ppm respectively. The optimum percentage removal was indicated in Table 2. b: dosage=0.2g,Time=60 mins and Temp. = 40 o C c: dosage=1g,Time=60 mins and Temp. = 25 o C CONCLUSION Poly Acrylamide was successfully grafted onto cellulose backbone obtained from old newspaper (CE) which improved it stability and it has been confirmed by FTIR and TGA analysis. FTIR results showed additional peaks on the entire grafted samples which was not observed on the ungrafted cellulose. Appearance of these band confirmed chemical modification of the cellulose. The TGA also indicate that the grafted cellulose (CE-g-PAAM) was thermally stable than the ungrafted cellulose (CE). It was also observed that CE-g-PAAM copolymer has an excellent adsorption capacity and can be used as an efficient and stable adsorbent material for the removal of heavy metal ions.