The Poisoning of Pyrite Surface upon Xanthate Adsorption by Cyanide in Mildly Acidic Media

Abstract

[a] 1Introduction Thea dsorption of organic species ontom inerala tt he solid-liquid interface is of significance for the establishmento fh ydrophobics urface,r enderingm inerals flotation possible.I ti sn ow well established thatt he interaction of typicalc ollector xanthate withp yrite, the most abundant sulfide minerals is electrochemicali nn ature [ 1].T he pyrite-xanthatei nteraction is affected by manyf actors sucha spH, redox potential,a nd differents olution species, in addition to the history of the mineral. It was reported [2-4] thatt he maximum flotationr ecoveryo fp yritei so bserveda tm ildly acidicp H( 3.5-5.5),e specially withl ow xanthate concentration. Thed epression at lower pH has been attributed to the decomposition of xanthatei ons [ 4]. Thec hemisorption of xanthatep resumably involves the oxidation of xanthatet od ixanthogeno np yrite [4][5][6][7][8]. Spectroscopics tudies [ 8] showt hatt he amount of adsorbed xanthater eaches am aximuma tp H5 after treatmentw ith1 0 À4 xanthate solution andd ecreases steadily withf urtheri ncreasingp H. Theg reater extent of hydrophilic ferric hydroxidecoverage on pyritewith the increasingpHisunfavorable for the adsorptionofxanthate [4,7]. Thepoorfloatabilityinneutral media hasalsobeenattributedt ot he formation of hydrophilicf erric dihydroxyx anthate,F e(OH) 2 EX, over apHrange from5to 9 [2,3].It was also revealed that cyanide inhibited all surface electrochemical activities, rendering pyrite surface hydrophilic [9][10][11][12][13][14].C yanide speciation largelyd epends on pH of the solution. Thec yanide anion in aqueous solution forms hydrocyanic acid (HCN)a ccording to the dissociation reaction in Equation (1) [15].Thel ogarithmic exponent of the dissociation constant pKa of HCN at 25 8Cis9 .21 [16].ApH value higher than 9.21 increases CN À concentration while ap Hvalue lower than 9.21 promotes the presence of aqueous HCN in the solution.C yanide consistently exists as HCN whenp Hi s lower than 7 [ 16].T hough numerous studies of this system were carried out, the depression mechanism of cyanide has been controversial and was postulated to be associated with the formation of iron-cyanide compounds on pyrite surface [17,18] or the inhibitiono fx anthate oxidation at reducingp otential in the presenceo fc yanide [13,19].F urthermore,t hose studies involving cyanidepyrite interaction were conducted at neutralt oa lkaline pH. Thex anthate chemisorption in the presenceo fH CN in mildly acidic media is unknown, whichi s, however, of great importance whent he maximum recovery of pyrite is desired in flotation, particularly for auriferous pyritic ore.Due to the maximum xanthate chemisorptiono np yrite can be achieved at pH 5[ 8],t he impact of HCN on pyrite-xanthate interaction was investigated at pH 5b y means of electrochemical measurements. 2Experimental MethodsAh and-picked naturalm assive cubic pyrite specimen originated fromS pain was used as workinge lectrode.X -ray fluorescence (XRF) analysis shows that the pyrite specimen had as ulfurc ontento f6 ...

Application of EIS technique to investigate the adsorption of different types of depressants on pyrite

“…The adsorption process is coupled with the charge transfer in the pyrite-collector/depressant system because it is generally agreed that the composition and structure of the surface products depend on the redox potential (Guo, 2016). Therefore, the adsorption behaviour of the depressants used in this study was evaluated based on coating layer resistance (Rct) values.…”

“…Thus, minimum errors were obtained. A similar equivalent circuit model was used to explain the electrochemical process on the pyrite electrode surface (Guo, 2016;Guo et al, 2016). Pyrite is a natural semiconductor, and the electrochemical reactions on the electrode surface can take place easily according to electrooxidation of reaction on pyrite surface in alkaline media.…”

“…investigated the effect of three lignosulfonate-based biopolymers (DP-1775, DP-1777, and DP-1778) as pyrite depressants using EIS, and showed that DP-1778 was the strongest depressant for pyrite, followed by DP-1775 and DP-1777 (Mu et al, 2016a). Studies on the adsorption behavior of the pyrite-xanthate-cyanide system at pH 5 via CV and EIS were performed by Guo (Guo, 2016). This study reported that the pyrite surface upon xanthate adsorption was poisoned by cyanide with the formation of an iron cyanide complex (Prestidge et al, 1993).…”

In Situ Characterization of the Locked Particle Behavior of Sulfide Minerals Using Non-Destructive Electrochemical Measurements

“…To investigate the possible electrochemical reactions upon adsorption and oxidation of the collector on the mineral surfaces, electrochemical methods were studied in the absence and presence of a certain amount of collector. The NaEX concentration was adjusted to 1×10 -4 M since this concentration has been commonly employed in flotation studies and has widespread applications in the literature [21][22][23].…”