Neutralization acidic wastes

In short process lines slurries are readily handled by centrifugal pumps with large clearances. When there is a distribution of sizes, the fine particles effectively form a homogeneous mixture of high density in which the settling velocities of larger particles are less than in clear liquid. Turbulence in the line also helps to keep particles in suspension. It is essential, however, to avoid dead spaces in which solids could accumulate and also to make provisions for periodic cleaning of the line. A coal-oil slurry used as fuel and acid waste neutralization with lime slurry are two examples of process applications. 

The ratio of reactants had to be controlled very closely to suppress these impurities. Recovery of the acrylamide product from the acid process was the most expensive and difficult part of the process. Large scale production depended on two different methods. If soHd crystalline monomer was desired, the acrylamide sulfate was neutralized with ammonia to yield ammonium sulfate. The acrylamide crystallized on cooling, leaving ammonium sulfate, which had to be disposed of in some way. The second method of purification involved ion exclusion (68), which utilized a sulfonic acid ion-exchange resin and produced a dilute solution of acrylamide in water. A dilute sulfuric acid waste stream was again produced, and, in either case, the waste stream represented a... 

Other developing or potential appHcations for lime are neutralization of tail gas from sulfuric acid plants, neutralization of waste hydrochloric and hydrofluoric acids and of nitrogen oxide (NO ) gases, scmbbing of stack gases from incinerators (qv), and of course, from small industrial coal-fired boilers. 

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

Improvements to the methanol reductant processes may be found in the patent Hterature. These include methods of operation to reduce acidity in the crystallisation 2one of the generator to promote crystallisation of sodium sulfate and to reduce sulfuric acid consumption (48). Other improvements sought are the elimination of formic acid and chlorine impurities from the chlorine dioxide, as weU as methods of recovering acid and sodium hydroxide, or acid and neutral sodium sulfate from the soHd sodium sesquisulfate salt waste stream (48—52). 

Neutralization. The choice of a reagent for pH adjustment depends on cost ease and safety of storage and handling effectiveness, eg, for removing heavy metals, buffet characteristics of the pH titration curve as they affect pH control and avadabihty. The three principal reagents for neutralization of acid wastes are sodium hydroxide, sodium carbonate, and hydrated calcium hydroxide. 

Zero Releases. If you have no releases of a toxic chemical to a particular medium, report either NA, not applicable, or 0, as appropriate. Report NA only when there is no possibility a release could occur to a specific media or off-site location. If a release to a specific media or off-site location could occur, but either no release occurred orthe annual aggregate release was less than 0.5 pounds, report zero. However, if you report zero releases, a basis of estimate must be provided in column B. For example, if hydrochloric acid is Involved in the facility processing activities but the facility neutralizes the wastestreams to a pH of 6-9, then the facility reports a 0 release for the chemical. If the facility has no underground injection well, it enters NA for that item on the form. If the facility does not landfill the acidic waste, it enters NA for landfills... 

Many similar incidents have occurred when a stirrer or circulating pump stopped. For example, an acidic waste stream in a tank was neutralized with chalk slurry. The operator realized that the liquid going to drain was too acidic. Looking around, he then found that the stirrer had stopped. He switched it on again. The acid and chalk, which had formed two separate layers, reacted violently, and the gas produced blew the bolted lid off the tank. 

Waste Treatment. Figure 2 outlines the current waste recovery and treatment processes, and proposed changes. Acid waste streams are sent through nitric acid and secondary plutonium recovery processes before being neutralized with potassium hydroxide and filtered. This stream and basic and laundry waste streams are sent to waste treatment. During waste treatment, the actinides in the aqueous waste are removed by three stages of hydroxide-iron carrier-flocculant precipitation. The filtrate solution is then evaporated to a solid with a spray dryer and the solids are cemented and sent to retrievable storage. 

One technique used in a number of facilities that utilize molten salt for metal surface treatment prior to pickling is to take advantage of the alkaline values generated in the molten salt bath in treating other wastes generated in the plant. When the bath is determined to be spent, it is in many instances manifested, hauled off-site, and land disposed. One technique is to take the solidified spent molten salt (molten salt is sold at ambient temperatures) and circulate acidic wastes generated in the facility over the material prior to entry into the waste treatment system. This in effect neutralizes the acid wastes and eliminates the requirements of manifesting and land disposal. 

Acidic wastes with a pH of <2.0 and alkaline wastes with a pH of >12.5 are defined as hazardous (40 CFR Part 261). To meet the regulatory definition of nonhazardous, acidic wastes must be neutralized to a pH of >2.0 by reducing the hydrogen ion concentration, and alkaline wastes must be neutralized to a pH of <12.5 by increasing the hydrogen ion concentration. 

Carbonates (limestone and dolomite) will dissolve in and neutralize acidic wastes with the following process ... 

The only means by which inorganic wastes can be rendered nonhazardous are dilution, isolation (as in deep-well injection), in some cases changes in oxidation state, and neutralization. Acidic wastes made up one-fifth of the injected waste volume and involved one-third of the injection wells in 1983. Most of the volume was from inorganic acids (hydrochloric, sulfuric, and nitric). Acid-base characteristics and neutralization were discussed in detail earlier, so the remainder of this section will focus on heavy metals and other hazardous inorganics (selenium and cyanide). 

Belle Glade Carbonate Hot acid Organic plant wastes Neutralization Bacterial sulfate reduction Methane production... 

As a result of dissolution of the limestone by the partly neutralized acid wastes, calcium concentrations more than doubled in the near-deep monitoring well 10 months after injection started in 1963,67 In early 1966, however, they dropped to background levels (about 200 mg/L), possibly in response to biochemical decomposition of the waste. In September 1968, after about 300 million gallons of the acidic, unneutralized waste had been injected, the calcium concentration began to increase again. An abrupt increase in calcium to 2700 mg/L accompanied by a decrease in pH to 4.75 in January 1969 led to the decision to plug the near-deep monitoring well. 

APEOs and their acidic and neutral metabolites can be halogenated to produce chlorinated and brominated products. The formation of these compounds has been reported during the chlorination processes at drinking water treatment plants [1,35,36] and after biological waste-water treatment [37]. 

AQUATECH Systems first commercial application is recycling waste HF/HNO- steel pickling acid as shown in Figure 7 above. As described earlier, the acid is neutralized with KOH to pH 10-11, filtered and sent to the AQUATECH cellstack for regeneration. The KF/KNO, mixed salt produces an HF/HNO, mixed acid suitable for stainless steel pickling Jand an equivalent amount of KOH used to neutralize the next batch of waste acid. The water balance is maintained by conventional electrodialysis which rejects excess water from the KF/KNO salt. This water is... 

Bases Used in the Manufacture of Explosives and Propellants Following are a few examples of bases used in expl plants and labs a)Ca hydroxide has been used as a catalyzer in some reactions and as neutralizer of acidic wastes from plants manufg acids, TNT, etc b)Ammonium hydroxide- as a neutralizer of acidic materials and as a purifier of crude TNT(such as was practiced during WWII at the Vest Virginia Ordnance Works). Its use in chem labs is very extensive c)Na hydroxide has been used in some plants for neutralizing acidic substances. For instance, red waters(< -v) of TNT plants are neutralized and made alkaline prior to their concn in stills. Lab uses include titrations of acids manufd at the plants d)K hydroxide has been used in labs of plants for colorimetric testing of TNT and DNT, etc... 

The liquid waste is stored for at least 6 y prior to solidification to reduce the decay heat (Fig. 16.8) by a factor of 10 or more. The first U.S. military fuel reprocessing wastes were stored as neutralized waste in mild steel tanks at the Hanford reservation in eastern Washington. These steel-lined, reinforced-concrete tanks were 500,000-1,000,000 gal in capacity with provisions for removal of waste heat and radiolysis products. Corrosion of several tanks occurred with the release of waste. Fortunately, the soil around these tanks retarded nuclide transport. A better (and more expensive) design for storage tanks was implemented at the Savannah River site in South Carolina consisting of a second steel tank inside of a Hanford-style tank. The storage of acid waste in these tanks has not encountered the corrosion problems seen with the Hanford tanks. 

A wide variety of treatment technologies to reduce the volume, change the physical or chemical form (e.g., incineration, solidification of a liquid waste, neutralization of acidic or basic waste), and suitably package the waste for subsequent management steps. 

The chemical treatment of wastes can result in the material being converted to products that are nontoxic and environmentally acceptable. The methods fall into several categories that include acid/base neutralization, oxidation or reduction, and precipitation of toxic ions as insoluble solids. Many of the disposal procedures suggested in this book fall into these categories. 

Uric acid (Fig. 6) is the main nitrogenous waste product of uricotelic organisms (reptiles, birds and insects), but is also formed in ureotelic organisms from the breakdown of the purine bases from DNA and RNA (see Topics FI and Gl). Some individuals have a high serum level of sodium urate (the predominant form of uric acid at neutral pH) which can lead to crystals of this compound being deposited in the joints and kidneys, a condition known as gout, a type of arthritis characterized by extremely painful joints. 

Acid waste waters from silicone production enter neutraliser 9, a concrete container with two agitators, lined with acid-resistant tile from epoxy resin. Here the waste waters are neutralised with lime milk, which is automatically sent from reservoirs 6 with pumps 8. The pumps automatically switch off when pH in the neutraliser is 8-10 and switch on when pH is below 5. Neutral waste waters continuously self-flow through a collector into receiving reservoir 10 as they accumulate, they are automatically sent with pumps 11 for averaging and mechanical purification. 

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