Spectrophotometric Study of Xanthate and Dixanthogen Solutions

Abstract

Xanthate solutions of pH 6-10, prepared from "aged" potassium ethyl xanthate crystals, KEtX, were investigated spectrophotometrically in the region 190-400 mp and showed coexistence of xanthate ions, EtX-, dixanthogen, (EtX)z, and carbon disulphide, CS2. Optical density measurements on the spectra of dixanthogen solutions led to the evaluation of: molar absorptivities of dixanthogen a t wavelengths corresponding to the two main bands in the xanthate ion spectrum, i.e. a t 301 mP-6130 liter/mole cm, and a t 226 mp-18,400 liter/mole cm; the solubility of dixanthogen, ca. 1.3XlO-j mole/liter; and the equilibrium constant, k = 3 X 10l0, of the reaction 2(EtX)? + 40H---t 4EtX-+ 2H20 + 0 2 , for solutions saturated with air a t atmospheric pressure. Simultaneous reactions leading t o decomposition of xanthate and/or dixanthogen species to alcohol and carbon disulphide have been detected by a strong band a t 206.5 mp due to CS2 (with an estimated molar absorptivity of the order of 60,000-70,000 liter/mole cm).The behavior of xanthates in solution (particularly their dissociation, decomposition on acidification, and oxidation) has been the subject of numerous investigations. Yet, owing t o the complexity of the xanthate systems, many aspects have not been clarified. 111 the recent papers of Majinla (1, 2) the relevant literature is reviewed and new data are presented (based on ultraviolet spectrophotometry) concerning the dissociation, decomposition, and stability constants of alkyl xanthates from methyl to amyl, and lead, nickel, and cobalt xanthate complexes. Solubilities of numerous metal xanthates have been correlated in great detail by Sheka and Kriss (3) while Wronski (4) discusses the effects of increased pH in xanthate solutions.In investigating the kinetics of xanthate adsorption from mixed solutions containing quaternary ammonium compounds the use of ultraviolet spectrophotometric analyses of these mixed solutions necessitated a preliminary study of various products of xanthate decomposition. The most probable reactions involved in the decomposition of xanthate solutions are hydrolysis and formation of xanthic acid, [I]; decomposition to alcohol and CS2, [ 2 ] ; and oxidation to dixanthogen, [3]:Of these reactions, the production of xanthic acid and the subsequent decomposition to alcohol and CS2, particularly in low pH regions, have been most recently studied by Iwasaki and Cooke (6), Kleiil et al. (7), and Majima (1). The oxidation t o dixanthogen has been considered irreversible and of little interest, particularly since tests with 0 2 bubbled through xanthate solutions indicated this to be a slow reaction (Iwasaki and Cooke (6), Rao and Patel (8)) ; dixanthogen itself has been considered insoluble in water and no analytical method appears to be available for accurate determination of small quantities of dixanthogen. 'On leave from the Institute

Surface Chemistry of Froth Flotation

“…Xanthate oxidation, reaction (IV), had been considered irreversible and dixanthogen unreactive. However, spectrophotometric studies on dixanthogen dispersions by Pomianowski and Leja (1963) showed that dixanthogen does react in alkaline solutions and reverts partly to xanthate and decomposes to CS2 (see studies by Tipman (1970) and Figures 5.5b and 5.7). Patel (1960, 1961) established that aqueous oxidation of xanthate ion to dixanthogen is catalyzed by multivalent reducible ions such as Cu2+ and Fe 3 +.…”

A Comparative Study on the Effect of Flotation Reagents on Growth and Iron Oxidation Activities of Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans

“…These increases are higher in the presence of L. ferrooxidans than in A. ferrooxidans tests (except in the presence of KIBX and KIPX) (Figure 1c,d). The instability of these collectors when pH < 3 could be an explanation for these increases, where the pH may increase as a result of the H + consumption from the solution for the decomposition of the collectors in the early stage of experiments (Equations (1) and (2)) [7,[22][23][24]. During the next 14 days, the ∆ pH decreased in all experiments.…”

“…During the measurement, until day 21, DO 2 values remain lower than the DO 2 value of the control test (−∆ DO 2 ) for A. ferrooxidans tests except for NaEX and KAX, which show the highest positive deviations (Figure 3a,b). The presence of unstable collectors in the low pH culture can limit the availability (i.e., transfer) of oxygen (xanthates are unstable in acidic solutions, and their instabilities increase by decreasing the pH [7,[22][23][24]). These reactions' inhibitory effect increase the DO 2 value [36][37][38].…”

“…The presence of unstable collectors in the low pH culture can limit the availability (i.e., transfer) of oxygen (xanthates are unstable in acidic solutions, and their instabilities increase by decreasing the pH [7,[22][23][24] (Figure 3f-g). …”

Challenges and opportunities in the recovery/rejection of trace elements in copper flotation-a review

“…Woods et al (1995) showed that diethyldixanthogen does not form on pure gold surfaces below +300 mV SHE. It is believed that oxygen in the pulp helps in xanthate adsorption (Woods, 1976) and oxidation to dixanthogen (Finkelstein, 1967), whilst at high concentration it inhibits xanthate adsorption because of metal hydroxide formation at the mineral surface (Pomianowski and Leja, 1963). That is, increasing oxygen content increases the Eh, which enhances xanthate interaction with the mineral surface (Kuopanportti et al, 1997(Kuopanportti et al, , 2000.…”