Chlorine-based washing

Potential hazards to humans may be connected with the use of chlorine-based washing systems. Apart from the direct occupational hazard, there are increasing concerns about the formation of potentially harmful by-products. Chlorine may react with organic compounds on the products and form hazardous organochlorines that are considered to be potential carcinogens (Beuchat, 1998 Betts and Everis, 2005). Betts and Everis (2005) suggest that a ban on the use of hypochlorite systems is likely in the future. 

The hexane extract is shaken with 1 1 H2S04 in a small separatory funnel for 1 min and the bottom H2S04 layer is discarded. Such acid wash may be repeated two or three times. The extract is then repeatedly washed with 20% KOH solution. Contact time must be minimized because KOH could degrade certain chlorinated dioxins and dibenzofurans. If acid-base washing is performed, the sample extract should be washed with 5% NaCl solution each time after acid and base washes, respectively. Acid-base partitioning cleanup may, however, be omitted completely if the sample is expected to be clean. 

Chaidez, C., M. Moreno, W. Rubio, M. Angulo, and B. Valdez. 2003. Comparison of the disinfection efficacy of chlorine-based products for inactivation of viral indicators and pathogenic bacteria in produce wash water. Int. J. Environ. Health Res. 13 295-302. 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Extra.ction St ige. The washing step after the chlorination stage removes the chlorine. In alkaline extraction, about 1.5—3.5% NaOH based on pulp is used. This typically amounts to about 55% of the CI2 demand used in the chlorination stage (% NaOH = 0.55 x % CI2 ). The target pH exiting the... 

Because of the reducing nature of the product gas, heteroatoms (sulfur, nitrogen, and chlorine) appear in reduced form, that is, sulfur appears as hydrogen sulfide, nitrogen as ammonia, and chlorine as hydrogen chloride. In most cases, these materials are scrubbed from the product gas before it is burned. Ammonia and HC1 are very water soluble and are easily removed by a water wash. A number of processes have been developed for H2S removal many of these process are based on absorption in solutions of amines, such as monoethanolamine (MEA). 

Properties provided by these finishes are mostly improved wet fastness, for example washing, water, perspiration and ironing fastness, then better light fastness and only to a small extent improved crocking and rubbing fastness. For other kinds of colour fastness, for example dry ironing, chlorine, peroxide and carbonisation, there are no known possibilities for improvement by an after treatment. The market importance of these finishes is based on customer preferences and economic production demands. For abetter understanding, each of these three quite different fastness improvements will be dealt with separately. 

The receiver containing the ethereal solution of trimethyl-stibine is kept in ice, and the stopper is replaced with a gas inlet tube connected to a cylinder of chlorine. The inlet tube should extend at least 2 cm. below the level of the liquid in the flask. The mixture is stirred slowly and chlorine is bubbled in until the slurry turns yellowish in color. The precipitate of trimethylantimony dichloride which has formed during the chlorination is removed by filtration on a fritted Buchner funnel and washed several times with ethyl ether. The yield of crude product is 95.9 g. (64.2% of theoretical based upon SbCls). 

The preparation of trimethylantimony diiodide is identical to that of trimethylantimony dichloride up to the point of the addition of chlorine. Instead of a gas inlet tube, an addition funnel is mounted on the flask containing the ice-cold distillate of ethyl ether and trimethylstibine. For a reaction carried out on the basis of 0.25 mol of anhydrous antimony(III) chloride, a solution of 63,5 g. (0.25 mol) of iodine in 400 ml. of ethyl ether is prepared. This solution is added dropwise to the cold distillate. Stirring is maintained and the addition is continued until the color of iodine persists. The precipitate of trimethylantimony diiodide is filtered off on a fritted Buchner fuimel and washed with ethyl ether. The jdeld of the crude product is 47.7 to 65.3 g. (45.0 to 61.8% of theoretical based upon antimony (III) chloride). The diiodide may be recrystallized from ethanol. Anal. Calcd. for (CH3) 3Sbl2 Sb, 28.95 C, 8.55 H, 2.16. Found Sb, 29.31 C, 8.16 H, 2.25. The checkers report that the foregoing syntheses are also satisfactory using one-half the amounts prescribed. 

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