Disposal, reaction hazard

It is the formation of this material which makes the reaction have a low atom economy and, owing to the cost of disposal (usually by conversion to calcium phosphate and disposal as hazardous waste), has limited its commercial usefulness to high value products. Several methods have been developed to recycle (Ph)3PO into (Ph)3P but these have proved more complex than might be expected. Typically the oxide is converted to the chloride which is reduced by heating with aluminium. Overall this recovery is expensive and also produces significant amounts of waste. 

Greer JS, Griwatz GH. 1980, Ultimate disposal of hazardous materials by reaction with liquid sodium. Control of Hazardous Material Spills, Proceedings of the 1980 National Conference on Control of Hazardous Material Spills 1 416-20. 

Leo Weitzman received his Ph.D. in chemical engineering from Purdue University. He is a consultant with 30 years of experience in the development, design, permitting, and operation of equipment and facilities for treating hazardous wastes and remediation debris. Dr. Weitzman has extensive experience in the disposal of hazardous waste and contaminated materials by thermal treatment, chemical reaction, solvent extraction, biological treatment, and stabilization. He has published over 40 technical papers... 

Disposal of hazardous waste is dangerous and expensive, even when the contents of the waste are identified. Fortunately, most chemical waste produced in a laboratory or work area is identifiable. When the contents of a reagent bottle, reaction flask, or gas cylinder are not identified, the process of disposal is more dangerous, expensive, and difficult. Without mitigating information, all unknown materials must be treated as if they were potentially lethal and hazardous. In all cases, chemical unknowns cannot be disposed of until a general profile of the unknown has been generated. Even then, the disposal cost is a premium. Additionally, there is a constant threat of personal injury or death to individuals who handle these potentially dangerous materials. No price tag can be attached to an avoidable personal injury. 

The development of environmentally acceptable incineration technologies for the disposal of hazardous wastes is dependent on an understanding of the roles of (1) atomization or method of introduction of the waste materials, (2) evaporation and condensed-phase reactions of the waste droplets in the incinerator environment, (3) turbulent mixing in the incinerator, (4) kinetics of the thermal degradation and oxidation of the chemical species in question, and (5) heat transfer in the incinerator. 

The Heck reaction and its variants are used routinely in drug synthesis, where the palladium catalysts can be recovered and recycled. Some Heck reactions can use water as the solvent, which eliminates the purchase and disposal of hazardous organic solvents. The following examples suggest the wide utility of the Heck reaction. 

As its title implies, this is a general reference covering the basics of environmental chemistry. Contents indude general chemistry (matter, atoms, elements), chemical reactions and equations, water pollution and treatment, geochemistry, agricultural chemistry, treatment and disposal of hazardous substances, toxicology and occupational health, and nuclear chemistry. 

Research laboratories vary widely with respect to facilities and support given to safety. Large laboratories may have several hundred chemists and an extensive network of co-workers, supervisors, safety officers, and hazardous-waste managers. They also, according to government regulations, have an extensive set of safety procedures and detailed practices for the storage and disposal of hazardous wastes. In small laboratories, the individual chemist may have to take care of aU these aspects of safety. Some laboratories may routinely deal with very hazardous materials and may mn aU reactions in hoods. Others may deal mainly with relatively innocuous compounds and have very limited hood fadHties. 

Waste products. Determine the proper procedures for dealing with the disposal of hazardous reaction waste products, derivatives and reaction intermediates, and unused reactants. 

Corrective Action Application At a hazardous waste treatment storage and disposal facility in Washington State, a cyanide-bearing waste required treatment. The influent waste stream contained 15 percent cyanide. Electrolytic oxidation was used to reduce the cyanide concentration to less than 5 percent. Alkaline chlorination was used to further reduce the cyanide concentration to 50 mg/1 (the cleanup objective). The electrolytic process was used as a first stage treatment because the heat of reaction, using alkaline chlorination to treat the concentrated cyanide waste, would be so great that it would melt the reactor tank. 

Near-critical water has been used as a medium for various C-C bond formation reactions including Friedel-Crafts alkylation and acylation (Eq. 7.12).30 In these reactions, near-critical water solubilizes the organics and acts as a source of both hydronium and hydroxide ions, thereby replacing the normally required hazardous solvents and catalysts that require subsequent neutralization and disposal. 

Sawhney BL. 1989. Movement of organic chemicals through landfill and hazardous waste disposal sites. In Reactions and movement of organic chemicals in soils. SSSA Special Publication no. 22, 447-474. 

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