Alkaline peroxide extraction

There are various alternative chemical pulping methods, some of them are alkali extraction [43], alkaline and sodium chlorite treatment [30], alkaline and peroxide extraction [44], organic solvent extraction [45], acidic method [46], liquid-phase oxidation or a combination of these treatments [42,47]. 

A multiwavelength approach might have been considered as an alternative to chemical derivatisation. Ruddle and Wilson [62] reported UV characterisation of PE extracts of three antioxidants (Topanol OC, Ionox 330 and Binox M), all with identical UV spectra and 7max = 277 nm, after reaction with nickel peroxide in alkaline ethanolic solutions, to induce marked differentiation in different solvents and allow positive identification. Nonionic surfactants of the type R0(CH2CH20) H were determined by UV spectrophotometry after derivatisation with tetrabromophenolphthalein ethyl ester potassium salt [34]. Magill and Becker [63] have described a rapid and sensitive spectrophotometric method to quantitate the peroxides present in the surfactants sorbitan monooleate and monostearate. The method, which relies on the peroxide conversion of iodide to iodine, works also for Polysorbate 60 and other surfactants and is more accurate than a titrimetric assay. 

An acetic acid solution of r-selenopyrine is treated with an excess of 30 per cent, hydrogen peroxide and the mixture diluted with water after standing for a short time. The solution is well cooled and made alkaline with sodium hydroxide solution, then extracted with ether, from which solution the selenone separates on evaporation. It is obtained as large, colourless needles, M.pt. 126° C., readily soluble in alcohol, ether, benzene or acetic acid, insoluble in water, aqueous alkalis pr dilute mineral acids. 

Step 4). The slightly alkaline aqueous solution is extracted five times with successive (800-1200 mL) portions of ether (peroxide-free). This combined ether extract is then distilled and the active residue treated first with 80 mL butyl alcohol and then with 1500 mL of petroleum ether as in Step 3. 

The oil is leached with 200-240 mL of cold 0.2 N NaOH solution, repeating the extraction 4 or 5 times, and combining and filtering the alkaline extract. This aqueous alkaline solution is then extracted with six successive portions of sulfuric ether using about 300 mL of peroxide-free ether extract. 

After the crude pulp is obtained from the alkaline sulfate process, it is bleached in stages with elemental chlorine, extracted with sodium hydroxide, and oxidized with calcium hypochlorite, chlorine dioxide, and hydrogen peroxide. This lightens it from a brown to a fight brown or even white (difficult) color. Chlorination of the aromatic rings of residual lignin is probably... 

Dimethylnitrosoamines were determined in smoked foodstuffs after oxidation to nitroamines [107]. A 1—5-pg amount of dimethylnitrosoamine in 2—10 pi of methylene chloride was added to 9 ml of a mixture of trifluoroacetic acid and 50% hydrogen peroxide (5 4). The solution was allowed to stand for 12—24 h, then poured over 10—15 g of ice, rendered alkaline by adding carefully 30—40 ml of 20% potassium carbonate solution and was extracted with two 50-ml portions of methylene chloride. The extract was dried with anhydrous sodium sulphate and concentrated to ca. 5 ml by evaporation on a water-bath. The concentrate was transferred quantitatively into a calibrated test-tube and 1 ml of n-hexane was added. Then it was further concentrated to 0.2 ml, made up to volume with n-pentane and 1—4 pi were injected. 

Oxidation in acidic solution can be achieved by Caro s acid, for example at 85 °C.247 This chemistry is employed in the extraction of chromium from superalloy scrap.248 It can also be used to detoxify, recover or re-cycle effluents from chromic acid oxidation or pickling liquors. Detoxification and recovery of chromic acid solutions is by the addition of hydrogen peroxide which reduces the chromium(III) salts, followed by alkali to precipitate and separate chromium hydroxide.249 Re-cycle can be by direct re-oxidation with Caro s acid, or by first raising the pH to alkaline levels, oxidation with hydrogen peroxide and re-acidification with subsequent salt by-product production. 

Recovery of vanadium with peroxygens involves both oxidation and com-plexation. In solution, conversion of lower oxidation states into vanadium(V) allows separation by solvent extraction (Figure 6.18).269 This chemistry can be used for vanadium by-products in uranium extractions. With hydrogen peroxide, vanadium(IV) is not oxidized in acidic solution, but rather in alkaline conditions, e.g. 60 °C at pH 9 (Figure 6.19).270 Use of excess hydrogen peroxide readily forms peroxo complexes and this is of value in selective dissolution of vanadium from secondary sources. 

---