Published: November 01, 2011 r2011 American Chemical Society 4691 dx.doi.org/10.1021/je2006677 | J. Chem. Eng. Data 2011, 56, 4691–4695 ARTICLE pubs.acs.org/jced Solubility of CO 2 in an Aqueous Blend of Diethanolamine and Trisodium Phosphate Hemant K. Balsora and Monoj K. Mondal* Department of Chemical Engineering and Technology, Institute of Technology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India ABSTRACT: This work presents experimental results on the solubility of CO 2 in a new blend of diethanolamine (DEA) and trisodium phosphate (TSP) at temperatures ranging from (303.14 to 333.14) K and partial pressures from (10.133 to 20.265) kPa. Total concentrations of aqueous DEA + TSP blends were taken as (1.0, 1.5, and 2.0) mol 3 dm À3 . In a particular blend, the mole fraction of TSP was in the range 0.02 to 0.20. The results show that CO 2 solubility in a blend with a particular total concentration increases with increasing mole fraction of TSP at fixed temperature and partial pressure of CO 2 . The solubility of CO 2 in the blend decreases with increasing temperature but increases with increasing CO 2 partial pressure. The maximum CO 2 solubility in DEA + TSP blends was found to be 0.869 (mol of CO 2 ) 3 (mol of absorbent) À1 at 313.14 K, a total concentration of 2.0 mol 3 dm À3 , and a TSP mole fraction of 0.2. The experimental results of the present study are compared with those for other blends available in the literature. ’ INTRODUCTION Fossil fuels are the main source of energy and also, unfortu- nately, of pollutants, greenhouse gases (GHGs), and other trace atmospheric varieties. Coal is the primary fuel in thermal power plants; gasoline and diesel are the primary fuels for automobiles. There is also limited use of natural gas in these energy activities. Combustion of fossil fuels releases a massive amount of CO 2 into the atmosphere. It has been reported that as a result of human activities, roughly (26 to 30) % of the total CO 2 comes from fossil fuel combustion used for electricity generation. 1À3 Scientists have found a direct relationship between CO 2 emissions and global warming and climate change (CO 2 accounts for more than approximately 55 % of the total observed global warming). 4 Amine-based chemical absorption is a well-established and mature technology among several technologies available to reduce CO 2 emission from industrial gas streams. Commonly used amines are monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), and di-2-propano- lamine (DIPA). 5,6 Other absorbents, such as diglycolamine (DGA), 2-(2-aminoethylamino)ethanol (AEE), 2-amino-2- methyl-1-pro- panol (AMP), N-(2-aminoethyl)-1,3-propanediamine (AEPDNH 2 ), triethanolamine (TEA), triethylenetetramine (TETA), piper- azine (PZ), glucosamine (GA), sodium hydroxide (NaOH), ammonia (NH 3 ), potassium carbonate (K 2 CO 3 ), potassium hydroxide (KOH), sodium carbonate (Na 2 CO 3 ), and so on w?>were also tested for CO 2 removal. Most of the amines mentioned have been used in large-scale units for CO 2 removal successfully for decades. Blends of alkanolamines have also recently been suggested to capitalize on the advantages of each amine (e.g., a primary or secondary alkanolamine and a tertiary alkanolamine or a steri- cally hindered alkanolamine). Activation of alkanolamine sol- vents for CO 2 removal to take advantage of a relatively high rate of reaction of CO 2 with the activating agent can be combined with the advantages of the high loading capacity of tertiary alkanolamines or hindered alkanolamines and the relatively low cost of regeneration of the activated solvent. 7 Many researchers have reported the absorption characteristics of CO 2 in blended amines. The low vapor pressure of DEA makes it suitable for low-pressure operations, as vaporization losses are quite negligible. Further, DEA solutions are less corrosive than MEA solutions. In view of this, DEA-based blends appear to be potential solvents for gas treatment processes. 8 The solubilities of CO 2 in various DEA blends have been reported in the literature. 8À14 Trisodium phosphate (TSP) is an inorganic solvent that is highly alkaline and nonvolatile in nature and undergoes negli- gible thermal degradation. It has properties suitable for use as an absorbent for acid gas treatment. There is no work listed to date in the literature concerning the solubility of CO 2 in aqueous blends of DEA and TSP. In this work, the absorption of CO 2 by aqueous blends of DEA and TSP has been experimentally studied to generate new solubility data at total blend concen- trations in the range (1.0 to 2.0) mol 3 dm À3 , temperatures from (303.14 to 333.14) K, and CO 2 partial pressures from (10.133 to 20.265) kPa. ’ EXPERIMENTAL SECTION Materials. All of the chemicals used were AR-grade. DEA with minimum purity 98 % (Sisco Research Laboratories Pvt. Ltd., Mumbai, India) was used to prepare amine blends. TSP with minimum purity 98 % (RFCL Ltd., New Delhi, India) was used without further purification. All solutions were prepared using deionized water. Two gas streams, one from a cylinder containing Special Issue: Kenneth N. Marsh Festschrift Received: July 4, 2011 Accepted: October 12, 2011