Xanthation process

Wastewater treatment in the copper sulfate industry can further be improved, particularly the removal of the toxic metals, through sulfide precipitation, ion exchange, and xanthate processes. Addition of ferric chloride alongside alkaline precipitation can improve the removal of arsenic in the wastewater. 

A more appropriate and improved method of treatment is still under study. The ion exchange and xanthate processes have not proved to be effective in treating the raw waste associated with this industry. 

One of the earlier methods was to treat cellulose with sodium hydroxide and carbon disulfide to obtain xanthate esters which could be dispersed in water and cast into sheets or spun into fibers. Subsequent treatment with acid decomposed the xanthates and gave regenerated cellulose, either in fiber or film form. The fibers were called viscose rayon and the films were named cellophane. Cellophane is still used as a wrapping film and some of it is still manufactured by the xanthate process. By treatment with nitric acid, cellulose was converted to a trinitric acid ester, which could be cast into units which were satisfactory for making gun cotton for a smokeless powder for either artillery shells or shotgun ammunition. It was quite insoluble but it could be converted to a jelly-like mass, which could be shaped into a desired form for ammunition use. Under milder conditions, a lower nitrate... 

An alternate procedure used in a few specialty applications is the cuprammonium process. This involves stabilization of cellulose in an ammonia solution of cupric oxide. Solubilization occurs by complex formation of cupric ion with ammonia and the hydroxyl groups of cellulose. Regeneration of cellulose, after formation of the desired products, is accomplished by treatment with acid. The main application of the cuprammonium process is for the synthesis of films and hollow fibers for use in artificial kidney dialysis machines. The cuprammonium process yields products with superior permeability and biocompatibility properties compared to the xanthation process. Less than 1% of all regenerated cellulose is produced by the cuprammonium process. 

Regenerated cellulose fibers are known as rayon and regenerated films as cellophane. They are made by the xanthate process, which uses sodium hydroxide and carbon disulfide ... 

The carbamate process, which uses urea as a modifying agent, represents a greener alternative to the xanthate process (Ekman el al., 1984). However, the industrial scale-up has not yet been successful. 

Ionic liquids are able to dissolve carbohydrates to high concentrations as mentioned in the previous section. The use of ionic liquids in cellulose dissolution and functionalisation is particularly significant considering the problems associated with conventional processes such as the cupramonium and xanthate processes [117, 118, 120, 134-136], Lignin is soluble in ionic liquids, as discussed in Sect. 4.2. 

It can also be made from sucrose by Acetobacter xylinum.71 This bacterial cellulose has high mechanical strength and might become an important material if the cost can be brought down. Regenerated cellulose fibers are known as rayon and regenerated films as cellophane. They are usually made by the xanthate process, which uses sodium hydroxide and carbon disulfide. 

Viscose rayon. The regenerated cellulose is prepared and sold as a fiber as well as a film, known as CHAPTER 7 cellophane, The viscose, or more properly referred to as the xanthate process, consists of forming... 

Materials, Solutions. Unless otherwise noted the cellulose used was Avtex rayon (cellulose regenerated via the xanthate process) of DP 300. Cellulose acetate of DP 700, DS 0.7 was used where noted. Solutions were prepared (or attempted) by using cellulose that had been vacuum dried at 70-75 for 12-20 hr, predried solvents and additives, and heat and/or stirring as noted. 

As indicated previously, the most important current method of preparing regenerated cellulose is by the viscose (or xanthate) process. The reactions involved in this process may be represented as follows ... 

Scheme 16.1 Chemical reaction for cellulose xanthate process.

Ubbelohde-Viskosimeter viscometric flow viskometrische StrOmung viscose fiber ViskoseFaser (CV) viscose process (xanthate process) ViskoseverFahren viscose silk/ viscose rayon/rayon Viskoseseide,... 

Carbon disulfide is used in the xanthation process to make rayon fiber. 

The xanthation process is complex because in addition to Reaction 10.2, many side reactions occur simultaneously upon the addition of CS. The following are some important side reactions ... 

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