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Oxalic acid is the simplest of dicarboxylic acid. Its name is derived from the Greek Oxyes
meaning sharp, acidic serfering to the acidity common in the foloage of certain plants from
which it was first isolated. Oxalic acid is commercially available as
the dihydrate containing 28.5% water. It is a monoclinic prism, particles size varying
from fine powder to coarse granules which are also Colorless , melting point 187oC of
anhydrous form and 101.5oC of dihydrate form. Oxalic acid is one of the most widespread organic acid in plants. In this project a commercial method of preparation of Oxalic acid at 30 ton per day is presented using molasses as the starting material. This project also highlights the material & energy balance as well as description of a few equpiments used in this process.
1.1 OXALIC ACID
Oxalic acid is an organic compound with the formula H2C2O4. It is a colourless crystalline solid that dissolves in water to give colourless solutions. It is classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic acid Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C2O42−), is a chelating agent for metal 
1.2 PHYSICAL & CHEMICAL PROPERTIES
Appearance... Transparent, colourless, odourless crystals. Solubility... 1gm/7ml (water).
Specific Gravity... 1.65
Boiling Point... 149 - 160°C (sublimes).
Melting Point... 101.5°C.
Vapour Density... 4.4 (air=1).
Vapour Pressure... < 0.001 @ 20°C (mm Hg).
Chemical Formula... HOOCCOOH.2H2O
Oxalic acid, is purchased usually in the form of oxalic acid dihydrate, which is a
crystallineform with two water molecules attached to each molecule of oxalic acid.Oxalic
acid is the simplest of dicarboxylic acid. Its name is derived from the Greek Oxeyes
meaning sharp, acidic suffering to the acidity common in the foliage of certain plants from
which it was first isolated. Oxalic acid is commercially available as
thedihydrate containing 28.5% water. Oxalic acid isodorless and white in colour. It is a
monoclinic prism, with particles size varying from fine powder to coarse granules which
are also colourless, melting point 187OCof anhydrous form .Oxalic acid is a normal
metabolite of carbohydrates in normal quantities, e.g., Fructose, Glycine, and Vitamin C.
1.3MOLASSES& ITS PROPERTIES
Molasses is a viscous by-product of the refining of sugarcane, grapes, or sugar beets into sugar. The word comes from the Portuguese―melaço‖, ultimately derived from Mel, the Latin word for "honey".The quality of molasses depends on the maturity of the source plant, the amount of sugar extracted, andthe method employed. Molasses are of various type based on plant material from which it is produced. So different type of molasses produced base upon on various raw material are cane molasses from sugarcane,beet molasses from sugar beet,grape molasses from grapes .Its major constituents are-
1) Glucose – 35.9%
3) Sucrose – 2.6%
4) Water - 23.5%
Uses of Molasses
• Molasses is commonly used with yeast and water in the fermentation process of making rum. It is also used in creating some other alcoholic drinks such as stout and dark ales.
• Some tobacco companies add it to their product for smoking through a certain type of pipe popular in the Middle Eastern countries.
• Some anglers use molasses as a groundbait (also called chum or berley). This is designed to attract fish to the area that an angler is fishing.
• It can also be mixed with water and used to remove rust.
• It is used in some horticultural settings to promote microbe activity in the soil.
• Molasses contains trace amounts of important vitamins and minerals. A certain type of molasses called blackstrap molasses has been sold as a health supplement for many years. People have made many claims about its health benefits, including the ability to prevent gray hair.
• Molasses is also added to some cattle feed to add essentials vitamins and minerals
Glucosea major component of molasses also known as D-glucose, dextrose, or grape sugar is a simplemonosaccharide foundinplants. It is one of the three dietary monosaccharide, along with Fructose and Galactose, that are absorbed directly into the bloodstream during digestion. An importantcarbohydrate in biology,cells use it as the primary source of energy and a metabolic intermediate. Glucoseisone of the main products of photosynthesis and Fuels forcellular respiration. Glucose exists in several different molecular structures, but all of these structures can be divided into two families of mirror-images(stereoisomers). Only one set of these isomers exists in nature, those derived from the"right-handed form" of glucose, denoted D-glucose. D-glucose is sometimes referred to as dextrose, although the use of this name is strongly discouraged. The term dextrose is derived fromdextrorotatory glucose.
This name is therefore confusing whenapplied to theenantiomer, which rotates light in the opposite direction. Starchandcellulose are polymers derived from the dehydration of D-glucose. The other stereoisomer, called L-glucose, is hardly ever found in nature.The name "glucose" comes from the Greek word glukusmeaning "sweet".
In this study optimization of oxalic acid production from Sweet Potato Starch Hydrolyzate (SPSH) using Aspergillusniger was investigated. The effects of three independent variables (concentrations of SPSH, fermentation time and pH) on the response (oxalic acid yield) and their reciprocal interactions were established using Response Surface Methodology (RSM). The box behnken design (BBD) was used to generate a total of 17 fermentation runs, which were subsequently conducted. A second-order mathematical model was obtained to predict the oxalic acid yield. A statistical model predicted the highest conversion yield of oxalic acid to be 103.274 g/l, at the optimal condition of SPSH of 149.97 g /l, time of 9 days, and pH of 6. The optimized condition was validated with the actual oxalic acid yield of 103.26g/l. This work revealed that sweet potato starch could serve as alternative carbon source for oxalic acid production and the results could be scaled up to industrial production.
Keywords: Sweet potato, Response Surface Methodology, Oxalic acid, Optimization, Aspergillusniger.
4.2 Ali Y. Bilgesu, Vecihi Pamuk(2000):-
Production of oxalic acid from sugar beet molasses was developed in a series of three reactors. Nitrogen oxides formed were used to manufacture oxalic acid in the second and third reactor. Parameters a acting the reaction were determined to be, air Low rate, temperature, the amount of V2O5 catalyst and the concentrations of molasses and H2SO4. The maximum yields in the second and third reactors were 78.9% and 74.6% of theoretical yield, respectively. Also, kinetic experiments were performed and the first-order rate constants were determined for the glucose consumption rate. Nitrogen oxides in o-gases from the reactor were absorbed in water and concentrated sulphuric acid and reused in the following reactors giving slightly lower yields under similar conditions. In this novel way, it was possible to recover NOx and to prevent air pollution. Meanwhile, it was possible to reduce the unit cost of reactant for oxalic acid production. A maximum 77.5% and 74.1% of theoretical yield was obtained by using the absorption solutions with NOx.
4.3 Harrison A. Emeko, Abraham O.Olugbogi, and Eriola Betiku(2015):-
This study assessed the effects and interactions of cashew apple juice (CAJ) concentration, pH, time, methanol concentration, and NaNO3 concentration on oxalic acid fermentation in a central composite design. The efficacies of artificial neural network (ANN) and response surface methodology (RSM) in modelling and optimizing the process were evaluated using correlation coefficient ®, coefficient of determination (R2), and absolute average deviation (AAD). The highest oxalic acid production observed was 120.66 g/L under optimum values of a CAJ concentration of 291 g/L, pH of 6.9, time of 10.82 days, methanol concentration of 2.91% (v/v), and NaNO3 concentration of 1.05 g/L that were numerically predicted by the developed RSM quadratic model. Using the developed ANN model coupled with rotation inherit optimization, the highest oxalic acid production observed was 286.75 g/L under the following optimum values: CAJ of 291 g/L,
pH of 6.5, time of 12.64 days, methanol concentration of 3.82% (v/v), and NaNO3 concentration of 2.41 g/L. The results showed that the ANN model (R= 0.9996, R2= 0.9999, AAD = 0.21%) was better than the RSM model (R= 0.9986, R2= 0.9973, AAD = 1.00%) for optimizing oxalic acid fermentation. The use of the ANN model led to a 2.4-fold increase in oxalic acid yield over the RSM model.
Keywords: Cashew apple juice; Oxalic acid; Central composite design; Fungi; Modeling.
4.4 Jiří Kaláb, Zdeněk Palatý(2012):-
Batch electro dialysis of aqueous solutions of oxalic acid was investigated using a laboratory electro dialyzer ED-Z mini equipped with ion-exchange membranes Ralex-AMH-PES and Ralex-CMH- PES (Mega, Stráž pod Ralskem, Czech Republic). The paper presents a mathematical model which enables to predict changes in the oxalic acid concentrations in the dilute and concentrate compartments during the electro dialysis process under various conditions specified by combinations of the initial acid concentrations with current densities. The calculation proved a good agreement between the developed model and the experimental results. c© 2012 Institute of Chemistry, Slovak Academy of Sciences
Keywords: oxalic acid, batch electro dialysis, mathematical modelling.
4.5 M.N. El Hazek, T.A. Lasheen, A.S. Helal(2009):-
Manganese leaching from a low-grade ore (8.52% Mn) from Sinai was investigated by using hydrochloric acid in the presence and absence of hydrogen peroxide as a reducing agent. Sample characterization by XRD showed the presence of a variety of manganese minerals mainly cryptomelane, chalcophanite, pyrolusite, and crednerite. The presence of iron minerals like goethite, hematite, and minor quantities of pyrite were also observed, as well as gibbsite and dolomite. Although pyrite can act as a reductant for the tetravalent manganese minerals, it was necessary to use H2O2as an additional reductant to realize over 97% Mn leaching. Both Zn and Cu that are present in the manganese minerals chalcophanite and crednerite respectively, were simultaneously leached.The relevant leaching factors were optimized as 2 M HCl and 0.4M H2O2 for1hwhenusingasolid–liquid ratio of 1/12 at 60–95 °C.Under these conditions, the leaching efficiencies were >97% Mn, 98% Zn together with about 81% Al and complete leaching of Cu;whilst iron dissolution did not exceed 14%.© 2006 Elsevier B.V. All rights reserved.
Keywords: Manganese ores; Hydrochloric acid leaching; Reductive leaching; Hydrogen peroxide.
4.6 Ruijter GJG, van de Vondervoort PJI, Visser J(2012):-
The external pH appeared to be the main factor governing oxalic acid production by Aspergillusniger. A glucose-oxidase-negative mutant produced substantial amounts of oxalic acid as long as the pH of the culture was 3 or higher. When pH was decreased below 2, no oxalic acid was formed. The activity of oxaloacetate acetylhydrolase (OAH), the enzyme believed to be responsible for oxalate formation in A. Niger, correlated with oxalate production. OAH was purified from A. Niger and characterized. OAH cleaves oxaloacetate to oxalate and acetate, but A. Niger never accumulated any acetate in the culture broth. Since an A. Niger acuA mutant, which lacks acetyl-CoA synthase, did produce some acetate, wild-type A. Niger is apparently able to catabolise acetate sufficiently fast to prevent its production. An A. Niger mutant, prtF28, previously isolated in a screen for strains deficient in extracellular protease expression, was shown here to be oxalate non-producing. The prtF28 mutant lacked OAH, implying that OAH is the only enzyme involved in oxalate production in A. Niger. In traditional citric acid fermentation low pH and absence of Mn2+ are prerequisites. Remarkably, a strain lacking both glucose oxidase (goxC) and OAH (prtF) produced citric acid from sugar substrates in a regular synthetic medium at pH 5 and under these conditions production was completely insensitive to Mn2+.
4.7 R. Andreozzi, V. Caprio, R. Marotta, V. Tufano(2013):-
A kinetic model is developed for the ozonation of oxalic acid catalyzed by solid MnO2. The rate of ozonation is limited by the adsorption of oxalic acid on the catalyst surface and by the deactivation of a fraction of the active sites, because of an irreversible reaction with ozone. Moreover, the model includes the ozonation of oxalic acid catalyzed by dissolved manganese. This kinetic model allows for a fairly good correlation of the experimental data when the average size of the catalyst particles is smaller than about 10 μm. When larger particles are employed, noticeable mass-transfer limitations are encountered, mainly deriving from the diffusion of both reactants from the liquid bulk to the solid surface (external and internal). The dependence of the rate constant on pH is experimentally determined and explained in terms of the changing chemical structure of the active sites and of the dissociation equilibrium of oxalic acid.
4.8 Jasper Sloothaak, Mike Schilders, Peter J Schaap and Leo H de Graaff(2014):-
Pectin is a structural heteropolysaccharide of the primary cell walls of plants and as such is a significant fraction of agricultural waste residues that is currently insufficiently used. Its main component, D-galacturonic acid, is anattractive substrate for bioconversion. The complete metabolic pathway is present in the genome of Aspergillusniger, that is used in this study. The objective was to identify the D-galacturonic acid transporter in A. nigerand to use this transporter to study D-galacturonic acid metabolism .We have functionally characterized the gene An14g04280 that encodes the D-galacturonic acid transporter in A. Niger. In a mixed sugar fermentation it was found that the An14g04280 overexpression strain, in contrast to theparent control strain, has a preference for D-galacturonic acid over D-xylose as substrate. Over expression of this transporter in A. Niger resulted in a strong increase of D-galacturonic acid uptake and induction of the D-galacturonic acid reductase activity, suggesting a metabolite controlled regulation of the endogenous D-galacturonic acid catabolic pathway.
Keywords: D-galacturonic acid; Pectin; Sustainable resources; Aspergillusniger; Trans membrane transport.
4.9 Wijittra Hongsiri• Bart Danon• Wiebren de Jong(2014):-
It is known that both acids and salts have apositive catalytic effect on the dehydration of pentoses to form furfural, a potentially attractive platform chemical. In this study the effects of the combined usage of an organic acid, instead of stronger mineral acids, and a saline catalyst is investigated. In order to assess these effects, the kinetics of pentose dehydration to furfural are studied using oxalic acid as the primary catalyst and NaCl or seawater as the secondary saline catalyst. The interactions between these two types of catalysts are complex and are, therefore, also assessed thermodynamically. The addition of salts lowers the activity coefficient of the hydronium ions, but simul- taneously favours the dissociation of the organic acid. It turned out that these two effects are of similar magnitude, resulting in a fairly constant hydronium ion activity. Because nonetheless higher furfural yields are obtained using the salts as a secondary catalyst, it is concluded that the salts influence the pentose dehydration mechanism directly. The final furfural yields obtained using oxalic acid as the primary catalyst were only slightly lower than those for similar experiments using HCl. The most distinctive difference between the two acids is the lower reaction rate ( and thus longer reaction times) when using oxalic acid. Finally, it was observed that if no acidic catalyst is used, the salts tend to catalyse a loss reaction, which is sup-pressed when an acid is present.
Keywords:- Furfural Pentose dehydration Oxalic acid Seawater Bio refinery.
4.10 Abbas J. Jinia* and Jyotsna R. Pandey(2016):-
The growth of doped KDP crystals was initiated at room temperature using gel technique. Hydrosilica gel medium was prepared with the help of Sodium Metasilicate (SMS) solution mixed with weak acid i.e. Acetic Acid. The Oxalic Acid used as dopant, caused slight shift in the frequency of functional group present in pure KDP, which was studied by Fourier Transform Infrared Spectroscopy (FTIR). The lattice parameters of the grown doped crystals were determined by powder X-ray diffraction pattern (XRD). Further the Oxalic Acid doped KDP crystals were subjected to Thermogravimetric Analysis. The melting point and decomposition temperature was determined from
this TGA/DTA characterization.