Chemicals recycling sodium hydroxide

Water from screens, cleaners, washers, thickeners, and flotation cells contain relatively high levels of ink. These waters also contain valuable chemicals, ie, sodium hydroxide and surfactants. Recycle of this water can save up to 10% ia chemical costs. 

Heavy metals often can be removed effectively by chemical precipitation in the form of carbonates, hydroxides, or sulfides. Sodium carbonate, sodium bisulfite, sodium hydroxide, and calcium oxide are all used as precipitation agents. The solids precipitate as a floe containing a large amount of water in the structure. The precipitated solids need to be separated by thickening or filtration and recycled if possible. If recycling is not possible, then the solids are usually disposed of to a landfill. 

Spills of endosulfan, according to FAOAVHO (1975a), should be cleaned up by first washing with 5% sodium hydroxide solution and then rinsing with large quantities of water. In addition, empty containers that held endosulfan residues should be rinsed two or three times with water while the sides are scrubbed, and once with 5% sodium hydroxide solution. Thus decontaminated, the empty containers can be recycled and used by pesticide manufacturers to package a chemical similar to endosulfan if the containers remain in good condition and if such reuse is not prohibited by federal, state, or local laws. 

Making paper without pollution requires that each part of the process be nonpolluting. The chemicals most commonly used in the production of pulp are NaOH and Na2 S. In modem paper mills, sulfur-containing by-products are scmbbed from the plant exhaust, and the aqueous sodium hydroxide is reclaimed and recycled. The fillers used to make paper opaque—titanium dioxide, calcium carbonate, and kaolin (a clay)—are natural, nonpolluting minerals. The polymer binders and sizers are relatively easy to recapture from the aqueous waste stream. 

Most of the scrubber liquor is cooled (105°F) and recycled in the raw state. Part of the cooled liquor is filtered to remove accumulated ash particles and flows through the pH meter, conductivity meter, and then the cooling spray. Another portion (without cooling) is filtered and flows to the regenerator at a controlled rate. As shown, sodium hydroxide solution also flows to the regenerator at a controlled rate. The mixture of solutions is heated to about 220°F, and chemical reaction releases the ammonia and steam these products return to the system under the force created by their vapor pressures. 

After the scrubbing operation, the solution of salts is exposed to sodium hydroxide solution chemical reaction releases ammonia and steam for recycle. 

The success of this process depends on the low solubility of calcium carbonate, which is also what allows this process to be used for small-scale production of sodium hydroxide by a batch process. For batch operation, the functions such as slaking, mixing, and settling may be carried out in the same wooden (or steel) vessel. Separate units are required for these steps in the continuous process. A further chemical feature important to the recycle of the spent lime of this process is the relatively easier thermal loss of carbon dioxide from calcium carbonate than from sodium carbonate. Since sodium bicarbonate (NaFICOs) may be calcined at 175°C to obtain carbon dioxide loss, it might be expected that sodium hydroxide could be made by heating sodium carbonate at a higher temperature followed by hydration of the resulting oxide (Eqs. 7.21 and 7.22). 

Waste paper stock destined for recycling is normally segregated into grades according to whether the original pulp was produced by chemical or mechanical methods. The separate stocks are then repulped (dispersed) in a hot dilute solution of sodium hydroxide, sodium phosphate, or sodium silicate in water, and cleaned via a series of raggers, cyclones, and screens. Self adhesive labels and tapes pose a perennial problem in recycle pulps that a recently developed test method may help to solve [70]. Standard printer s inks... 

Acetone and phenol can be recovered after the neutralization of the acidic mixture from the cleavage reactor with sodium hydroxide or phenolate solution. The neutralized mixture is then subjected to a series of distillations. Acetone is first distilled, then cumene is recovered, together with a-methylstyrene, which is either purified and marketed or hydrogenated back to cumene and recycled to the oxidation. Phenol is finally distilled with a purity up to 99.99%, suitable for the production of polycarbonate grade bisphenol A and other chemicals and polymers. 

Long fibred pulp is used as the raw material. For the first step, it is treated with a diluted sodium hydroxide solution (approximately 15 %). Afterwards, the liquid is removed by pressing and then it is recycled back into the process together with fresh NaOH. Next, the pulp sheets are defibrated, pre-ripened and put into CS2 for chemical conversion to xanthate. After the addition of aqueous NaOH, the viscose emerges which is ripened and degassed in vacuum prior to spinning. 

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