The Preparation and Characterization of Starch Oxidized by Nitric acid and its Properties of Calcium Complexing Capacity

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1 Advanced Materials Research nline: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland The Preparation and Characterization of Starch xidized by Nitric acid and its Properties of Calcium Complexing Capacity Xuechuan Wang 1, a, Feihu Li 1,b and Taotao Qiang 1,c 1 College of Resource and Environment, Shaanxi University of Science and Technology, Xi an , China a wxc-mail@163.com, b lifeihu860118@163.com, c qiangtt515@163.com Keywords: oxidized starch; nitric acid; complexing capacity. Abstract. The primary hydroxyl groups of Starch xidized by nitric acid to the corresponding carboxylic acids has been investigated. The structure of the xidized-starch(s) was characterized by FT-IR, 1 HNMR and GPC. The predicated product was obtained from the results. Its application in calcium complexing capacity has been discussed. The calcium complexing capacity of S may up to mg/g. The data confirmed that the starch oxidized by nitric acid had excellent capacity of calcium complexing. Introduction The surfactants in detergents would react with calcium and magnesium ions when the detergents used in water, which would limits the applications of detergent. The sodium tripolyphosphate(stpp) used in the detergent as builder to complexing with calcium and magnesium ions,but the usage of STPP has become a environmental pollution all over the world.the carboxymethyl cellulose(cmc), zeolite and polyacrylic salt are used as substitutes at present, but their application effects are not satisfying. The high price of CMC would push up the cost of detergent, so it is difficult to popularize. Zeolite has low complexing capacity on metal ions and adds pollution to the environment. Polyacrylic salt is difficult to biodegrade and pollutes environment. Researching of new complexing agent with low price, good performance and biodegradable used in the detergent is an important front problem. Meanwhile, starch is generally regarded as a safe and renewable source because they are expected to be biodegradable. Starch after physical and chemical modifications is used in paper coating, medicine, detergent and other fields in recent years [1]. xidized starch (S) and carboxymethyl starch (CMS) as builders in detergent are one of the hottest issues in recent years [2-4], their carboxyl group can complexing with the metal ions. The effect of CMS as builder in detergent is very good, but the right CMS has to use organic as a solvent. The organic solvent in processed CMS is difficult to recycle, it will increase the cost. S does not have the same trouble as CMS, but the different oxidants bring different carboxyl degree of substitution and molecular mass. So some oxidizing chemicals, like nitric acid and sodium hypochlorite with strong oxidizing, are suitable for oxidant. The S not only has a high carboxyl degree of substitution, but also has low molecular mass after oxidized by nitric acid. So compared to other oxidizing chemicals, nitric acid is more suitable for this. The overall reaction figure for starch oxidation in the presence of the vanadium catalyst and nitric acid are shown in Fig. 1. Fig.1 Reaction Figure for Starch xidation: Carboxyl Groups Are Formed All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-06/03/16,16:16:56)

2 1594 Advances in Materials and Materials Processing The oxidation is, primarily at the C6 position with some oxidation occurring at the C2, C3 position. The oxidation converted the C6 position first to aldehyde, and then converted the C6 position to carboxyl group. It also converted some C2, C3 positions to carboxyl group. But first C2, C3 positions was oxidized to ketones, and then vanadium catalyst broke normal bonds between C2 and C3, the oxidation finally converted the C2, C3 positions to carboxyl group. Experimental Material. Native starch was purchased from Tianjin Tianli Chemical Reagent Co., LTD. Nitric acid (70 wt %, Beijing Chemical Factory) was utilized as an oxidant. Ammonium metavanadate was purchased from Tianjin Bodi Chemical Reagent Co., LTD. CMS was purchased from Henan Jincheng Chemical Reagent Co., LTD. The carboxyl group content was determined by titration with M NaH. Starch xidation. The experiments were performed in a 500mL glass reactor. Typically, 100 g of starch (0.62M glucoside) was suspended in a total volume of 100mL of deionized water at room temperature and added into the reactor, after which it was heated up to the desired temperature (20-30 C) and the vanadium catalyst was added to the desired amount ( g). Nitric acid (70 wt %, mol) was slowly added and react in different time (4-8h). In the experiments, the carboxyl degree of substitution of the S was studied in these different situations. When the reaction finished, cool down for a while. Added anhydrous ethanol, a precipitant is formed. The precipitant was taken out to a reagent bottles, it was washed by 21% sodium carbonate until the ph of solution to 7.The precipitant finally was centrifuged and stoved to obtain the product. The temperature, molar ratio between nitric acid and starch glucoside, time, and mount of catalyst were added according to Tab. 1. numbers Factors temperature [ C] Tab.1 rthogonal Test molar ratio between nitric acid and starch glucoside Time[h] mount of catalyst[%] : : : Complexation. The calcium complexing capacity of the S was determined by the method of Fluoride ion (F)-selective electrode [5]. FTIR analysis. The FTIR spectra were recorded on a Perkin Elmer System 1600 FTIR with an attenuated total reflectance (ATR) device from SPECAC. Sample wafers consisted of 1% sample diluted KBr. The sample cell was purged with a flow of dry C 2 during the measurements, 100 scans were accumulated for each spectrum in transmission at a spectral resolution of 4 cm 1. 1 H NMR analysis. 1 H NMR of samples was performed at the solid state using on a INVA-200 spectrometer. The samples were spinning at 3.54 khz in a zirconium oxide rotor. Molecular Weights analysis. The molecular weights of samples were recorded on a gel filtration chromatograph device from WATERS. Measurement temperature is 25, mol/l NaN 3 as the solvent, the flow rate is 1 ml/min. Results and discussion Starch xidation Technology. Sulfuric acid was added in to the oxidizing reaction as dispersing agent in the former studies [6]. Although sulfuric acid was produced useful, it also increased the complexity for the reaction. The mixture of sulfuric acid and nitric acid was difficult to recycle. The

3 Advanced Materials Research Vols experiment was simple without of sulfuric acid, and the nitric acid was easy to recycle. The technology reduced the carboxyl degree of substitution (DS CH ) of S. But the calcium complexing capacity of S was enough for detergent builder. Carboxyl groups content. According to Tab. 1 designed, the most mount of carboxyl group of S is found. This experiment repeats 3times, the data average. The highest degree of substitution carboxyl group (DS CH ) is The optimum conditions of oxidation are: 25, 6h, the ratio of catalyst 0.15%, the ratio of moles between nitric acid and glucose glycoside is 3:1. Fourier transform infrared spectroscopy. Fig.2 shows the FTIR spectra of S. According to the reaction mechanism and the expected products, the bands in the spectra corresponded to oxygen containing groups, i.e., the hydroxyl bands, have to change after oxidation. We can obvious observe the bands characteristic for the carbonyl groups (at about 1700cm -1 ) in the spectra for starch before and after oxidized. The hydroxyl group is electro-withdraw group. It will reduce the polarity of carbonyl group nearby. The rate of carbonyl stretching bands is changed from low to high for that reason. Fig.2 ruled out the possibility of aldehyde group existence because there is no characteristic adsorption peak in 2700cm -1. Fig.2 FTIR Spectra of Starch (a) Before and (b) After xidized H nuclear magnetic resonance spectrum. The S was analyzed using 1 H NMR spectrum from Fig.3. The 1 H NMR of the oxidation product shows a carboxyl hydrogen resonance at ppm. This shows the same information from FTIR. That is carboxyl group does exist in the S. So S is oxidized by nitric acid without sulfuric acid as dispersant can still generate carboxyl group. Fig.3 1 HNMR Spectra of xidized Starch Gel Permeation Chromatography. Tab. 2 shows that the molecular mass distribution of S is narrow. The molecular mass of S gets great decrease compare with native starch. Starch degrades when is oxidized by nitric acid. The more time reaction takes, the less molecular mass S has. Tab.2 Average Molecular Weights and Polydispersity Index of Native Starch and S Sample M n M w polydispersity index Native Starch S

4 1596 Advances in Materials and Materials Processing Complexation. The functional groups present in S such as hydroxyl and carboxyl act as active sites. The complex of Ca 2+ ions with these groups is presented below through Fig. 4. CH H H + Ca2+ n CH HC Ca 2 + H+ H Fig.4 Reaction Figure for Complexation The calcium complexing capacity is the important indicator to evaluate a builder in detergent. S belongs to carboxyl type complexing agent, its carboxyl can capture and store calcium ion. The Tab.3 shows the calcium complexing capacity of S and CMS. Tab.3 Calcium Complexing Capacity of S and CMS Sample The Calcium Complexing Capacity mg/g S CMS The calcium complexing capacity of the S is better than CMS from the Tab.3. S is a kind of organic weak acid, which can form a conjugated system in the washing liquid. Conjugate effect can form a buffer solution. If acid or base is added in a specific range, ph will not change much. The critical micelle concentration of washing liquid will degrade after the calcium ion is complexed. The washed dirt is hard to deposit on the clothing surface. The fluidity of washing liquid will be improved at the same time. The powder product is not easy to agglomerate. So the detergent quality will be improved, thus the dosage of detergent will be reduced. Conclusion Temperature, time, dosage of catalyst and nitric acid, all have impact on the oxidation reaction. The optimum conditions of oxidation are: 25, 6h, the ratio of catalyst 0.15%, the ratio of moles between nitric acid and glucose glycoside is 3:1. We demonstrated that the use of FT-IR spectroscopy is versatile tool for the characterization of the carboxylic acid. This could be demonstrated in combination with 1H NMR investigations. The S oxidized by nitric acid without sulfuric acid has suitable molecular mass and performs well as a builder in detergent. Acknowledgements This work was financially supported by the Shaanxi Province International Cooperation Program (2011KW-13) and Shaanxi University of Science and Technology Innovation Program for Graduate Students. References [1] J.BeMiller, R.Whistler: Starch Chemistry and Technology (Academic Press, America 2009) [2] Hodgetts, Robert W. Garvey, James M, et al. E.P.Patent 0,763,593. (2003) [3] Artiga Gonzalez, Lietzmann.U.S.Patent 6,528,474. (2003) [4] Arie C. Besemer, Jan M. Jetten, Ted M. Slaghek. Starch. 55 Vol (2003). [5] Yanxiao Chen, Gongying Wang. Journal of Applied Polymer Science. 102 Vol (2006). [6] H. Kochkar, M. Morawietz, W.F. Hölderich, Applied Catalysis A. 210 Vol (2001)

5 Advances in Materials and Materials Processing / The Preparation and Characterization of Starch xidized by Nitric Acid and its Properties of Calcium Complexing Capacity /

Division of Fuel Cells, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese

Division of Fuel Cells, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Electronic Supplementary Material (ESI) for RSC Advances. This journal is The Royal Society of Chemistry 2016 Supporting information Tuned Depositing Ag clusters on ZrO 2 Nanocrystals from Silver Mirror