Collectors For Flotation Of Minerals Research Articles

Study on quantitative structure–activity relationship of amine surfactants in coal reverse flotation

AbstractWith the deterioration of underground coal quality, hundreds of millions of tons of coal slime in China need to be treated using flotation methods every year. However, the design and selection of coal slurry flotation collectors lack theoretical guidance. In this paper, the quantitative structure–activity relationship (QSAR) model between the molecular structure descriptors of collectors and the flotation recovery and selectivity index is established by using pure kaolinite/clean coal flotation experiments and molecular simulation techniques. Flotation results showed that the flotation recovery rate of kaolinite by collectors with larger head group size, such as DDMAC, DDP, and DTAC, is higher than that of the other collectors with smaller head group size. DDA, DDP, and DD have similar flotation capabilities for clean coal, and their selectivity was slightly better than others. The QSAR model between the molecular structure descriptor and the selectivity index was successfully constructed by combining flotation experiments and molecular simulation results. The reliability of this model has been proven through theoretical analysis and flotation experiments. The molecular simulation results indicate that all eight collectors can advertise on 001 (−) surface of kaolinite, but the final advertisement configuration is different. DDA has less coverage on the surface of kaolinite. When the collector is DDA, the concentration of water molecules near the 001 (−) surface of kaolinite is the highest, indicating that the collector DDA has the weakest effect on improving the hydrophobicity of the 001 (−) surface of kaolinite. DDMAC and DDBAC have the best facilitation to the surface hydrophobicity of kaolinite 001 (−). The research results have theoretical guidance significance for the selection and design of mineral flotation collectors.

Novel multiple ligand metal-group collectors assembled from benzohydroxamic acid and cupferron

Pb–BHA (lead complexes of benzohydroxamic acid) as metal-group collectors have been recently used for mineral flotation collector. This complex possessed high selectivity but low flotation efficiency due to extensive dosage. To improve the flotation performance of Pb–BHA, we designed a novel multiple ligand complex collector assembled from Pb2+, BHA, and cupferron (CPF) (i.e., Pb–BHA–CPF). The flotation performance of Pb–BHA–CPF was studied through the flotation test. The structure of Pb–BHA–CPF was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the adsorption mechanism of Pb–BHA–CPF at the solid–liquid interface was investigated and discussed through the zeta potential, FTIR, XPS, and crystal chemistry analyses. Based on the results, Pb–BHA–CPF exhibited stronger collecting ability and selectivity than Pb–BHA at a lower reagent dosage. Structural analysis revealed that BHA and CPF could coordinate with Pb2+ to form novel multiple ligand complexes with lead groups, and CPF may replace BHA to form the molecular structure of Pb(L1)n(L2)m (HL1 = BHA, NH4L2 = CPF, n > m). The adsorption mechanism analysis indicated that Pb–BHA–CPF had stronger electrostatic attraction than Pb–BHA and showed stronger chemical adsorption strength with the active oxygen atoms on the mineral surface. This study proposed a method for designing and assembling a multiple ligand metal-group collector.

Unravelling the performance of oxycarbonyl-thiocarbamate collectors on chalcopyrite using first-principles calculations and micro-flotation recoveries

First-principle quantum mechanical density functional theory (DFT) was employed to explore the bonding behaviour, adsorption energies and electronic properties directly related to the reactivity’s of O-butyl-N-ethoxycarbonyl-thiocarbamate (BECTC), O-isobutyl-N-ethoxycarbonyl-thiocarbamate (IBECTC), O-butyl-N-butoxycarbonyl-thiocarbamate (BBCTC), O-isobutyl-N-butoxycarbonyl-thiocarbamate (IBBCTC), and O-isobutyl-N-isobutoxycarbonyl-thiocarbamate (IBIBCTC) with the chalcopyrite (CuFeS2) (112) surface and complimented by micro-flotation recoveries of the chalcopyrite. The partial density of states (PDOS) of the isolated oxycarbonyl-thiocarbamate collector showed that the sulphur atom (S1) was more active and will be more reactive during adsorption. Adsorption of the oxycarbonyl-thiocarbamate collectors preferred the Cu atom over Fe atoms. The adsorption energies and micro-flotation recoveries yielded similar trends and the order followed: BBCTC > IBIBCTC > BECTC > IBBCTC > IBECTC, which showed that BBCTC exhibited the strongest exothermic adsorption. This showed that the adsorption energies that determined how a collector binds to the mineral surface can predict the flotation recoveries. The PDOS and atomic population charges after adsorption showed that both Cu and S1 atoms lose charges (electron donor) forming σ-bonds, and simultaneously, dative π-bonds. The results also showed that BBCTC and BECTC are better collectors for the selective flotation of chalcopyrite minerals and indicated that a straight hydrocarbon chain gave stronger adsorption than a branched hydrocarbon chain.

Molecular Biology-Based Analysis of the Interactive Effect of Nickel and Xanthates on Soil Bacterial Community Diversity and Structure

Metals and mineral flotation collector’s toxicity to the soil living system greatly compromise the sustainability of mining and ore processing. Their effects on the soil microbial community, the most active soil component, remain less understood and addressed particularly with regards to xanthates and their combination with metals. This study analyzed the interactive effects of Ni and xanthates, potassium ethyl xanthate and sodium isopropyl xanthate, on the soil bacterial community through an efficient molecular biology-based technique, the Miseq (Illumina). Both soil microbial community diversity and structure were more affected by xanthates than by Ni. The five most dominant phyla, representing 96.31% of the whole bacterial community, comprised Proteobacteria (54.16%), Firmicutes (17.51%), Actinobacteria (15.59%), Acidobacteria (4.87%), and Chloroflexi (4.16%). Different soil treatments exhibited greater difference in the species abundance/dominance than in the species numbers. Proteobacteria was the most dominant in the presence of xanthates, individually or in mixtures with nickel, while Firmicutes exhibited its highest proportion in the Ni/xanthate-treated samples. The most abundant and proportionally different bacterial species between different treatments were presented. The most abundant bacterial strains identified should be explored more for their potential application in biomining and for the prediction and biologically-based treatment and remediation of Ni and xanthate-contaminated systems.

Interactive Effect of Copper and Its Mineral Collectors on Soil Microbial Activity—A Microcalorimetric Analysis

Discharge of metals and their mineral flotation collectors into the soil environment causes severe ecological and health impacts, which is still not fully understood. This is of great concern, particularly with regards to their effect on the soil microorganisms whose functions determine not only the soil quality and function but also influence the air and water quality. This study aimed to analyze and compare, microcalorimetrically, the single chemical toxic effect with the combined effect of copper (Cu) and two of its main flotation collectors, potassium amyl xanthate (PAX) and sodium isoamyl xanthate (SIAX), on soil microbial community. All chemicals, individually and as a binary mixture of copper and each of its flotation collectors, exhibited a significant dose-effect relationship, and the highest and lowest microbial activity inhibition being associated with SIAX and Cu, respectively (e.g. IC 50 of 447.5, 158.3 and 83.9 μg·g−1 soil for copper, PAX and SIAX, respectively). For all cases, the microbial activity was more affected by the mixture than by the individual mixture components. Increasing the xanthates dose (from 25 to 100 μg·g−1 soil) in the mixture with a copper dose of 200 μg·g−1 soil led to the increase of the microbial activity inhibition rate, from 23.08 % to 53.85% in case of PAX and from 26.92% to 57.69% in case of SIAX). Similarly, the toxicity level of the mixture of equitoxic components doses increased with the increased mixture doses. Since the observed activity level can be attributed to the surviving microbes, capable of adapting to both chemical and their mixture, a genetically based analysis should be conducted to allow identifying and characterizing the potentially resistant strains that can be useful for the remediation of the pollution by copper and xanthates and for the sustainability of copper mining and flotation, and for all soil, water, and air quality and function interest.

Choosing mineral flotation collectors from large nanoparticle libraries

Polystyrene nanoparticles can promote froth flotation of mineral particles if the nanoparticles are sufficiently hydrophobic and are colloidally stable in the high ionic strength solutions typical of commercial flotation operations. A library of 80 unique polystyrene nanoparticle types was prepared with click chemistry and used to determine if particles that were sufficiently hydrophilic to be colloidally stable in high ionic strength and high pH solutions, were also capable of promoting flotation. The conflicting requirements of colloidal stability and hydrophobicity can be achieved in 9 mM sodium carbonate, a very challenging environment. Instead of testing all 80 samples with laborious flotation testing, automated assays measuring colloid stability and nanoparticle hydrophobicity were employed. The colloid stability assay measured the critical coagulation concentrations (CCC). Nanoparticle hydrophobicity was characterized by water contact angle, measurements (CA). A smaller cohort of the most promising nanoparticle candidates for detailed flotation testing were identified by mapping nanoparticle properties on the CA versus CCC plain – a “Flotation Domain Diagram”. We believe that this work was the first time that combinatorial synthesis and high throughput screening have been used in the development of flotation chemicals. Finally, based on the accumulated evidence, effective nanoparticle flotation collectors are likely to be ∼50 nm in diameter, with a soft hydrophobic polymer shell and with surface functional group densities in the order of magnitude of 0.1 nm−2.

Removal of the residual xanthate from flotation plant tailings using modified bentonite

Xanthates are the most widely used collectors for flotation of sulfide minerals. It has been estimated that about half of the organic reagents (including xanthate) added to the flotation circuits are consumed, while the remaining half are discharged into the plant tailing. The residual xanthate in the flotation tailing can cause environmental issues through contaminating of the nearby water resources as a result of poor design of the tailings dams. In this communication two modified bentonite adsorbents, namely acid-activated (H-Be) and aluminum-pillared (Al-Be) bentonite, were synthesized and used for the removal of the residual xanthate (potassium amyl xanthate) from the synthetic and real solutions.Al-Be was found superior to H-Be in terms of adsorption performance and under optimum conditions (adsorbent dosage: 7500 mg/L; xanthate concentration: 2000 mg/L; pH = 12.2; time = 45 min) and more than 99% of the residual xanthate was removed. The kinetics data were best described by pseudo-second order model for the both adsorbents. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir, and Temkin models. The isotherm data were best-fitted to the Langmuir model, indicating monolayer adsorption of the xanthate on homogenous surfaces of the both adsorbents. The thermodynamics studies indicated that the adsorption was spontaneous, exothermic with the reducing entropy. The adsorption tests on the real samples taken from the tailing stream of a copper flotation plant (Qaleh-Zari in Iran) proved that both adsorbents are capable of removing more than 90% of the residual xanthate.

Cu(I)/Cu(II) mixed-valence surface complexes of S-[(2-hydroxyamino)-2-oxoethyl]-N,N-dibutyldithiocarbamate: Hydrophobic mechanism to malachite flotation

HypothesisHydroxamate and sulfhydryl surfactants are effective collectors for flotation of copper minerals. The combination application of hydroxamate and sulfhydryl collectors has been proved to be an effective approach for improving the flotation recovery of non-sulfide copper minerals. A surfactant owing both hydroxamate and dithiocarbamate groups might exhibit strong affinity to non-sulfide copper minerals through double sites adsorption, rendering an enhanced hydrophobization to non-sulfide copper minerals flotation. ExperimentsThe flotation performance of S-[(2-hydroxyamino)-2-oxoethyl]- N,N-dibutyldithiocarbamate (HABTC) to malachite, calcite and quartz were first evaluated through systematic micro-flotation experiments. HABTC's hydrophobic mechanism to malachite was further investigated and analyzed by zeta potential, Fourier transform infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). FindingsThe micro-flotation results demonstrated HABTC was an excellent collector for malachite flotation and exhibited favorable selectivity for flotation separation of malachite from quartz or calcite under pH 8.5–10.3. Zeta potential and FTIR implied that HABTC might bond with the surface copper atoms of malachite, with releasing the H+ ions of its hydroxamate group into pulp. ToF-SIMS provided clear evidences that the Cu-hydroxamate and Cu-dithiocarbamate groups were formed on malachite surfaces after HABTC adsorption. XPS revealed that Cu(I)/Cu(II) mixed-valence surface complexes of HABTC anchored on malachite through formation of Cu(I)S and Cu(II)O bonds, accompanying with reduction of partial surface Cu(II) to Cu(I). The Cu(I)/Cu(II) mixed-valence double chelating character and “chair”-shape N,N-dibutyldithiocarbamate hydrophobic group, resulting in an enhanced affinity and hydrophobization of HABTC to malachite flotation.

Evaluating the primary and ready biodegradability of dianilinodithiophosphoric acid.

Dianilinodithiophosphoric acid (DDA) is widely used as sulfide mineral flotation collector in China. It is necessary to investigate the biodegradability of DDA to provide the fundamental knowledge to assess the environmental fate in the risk assessment of DDA and to design and operate the DDA flotation wastewater biological treatment plant. In the present study, the primary and ready aerobic biodegradations of DDA were studied and the primary biodegradation kinetic model of DDA was developed. The results show that DDA displays a good primary biodegradability and its biodegradation ratio reaches 99.8% in 7days. In contrast, DDA is not easily ready biodegradable; hence, it is a partially biodegradable organic compound. The primary aerobic biodegradation kinetics can be described using the first-order reaction kinetics equation: C = 19.72191e(-0.01513t).

Effect of three typical sulfide mineral flotation collectors on soil microbial activity.

The sulfide mineral flotation collectors are wildly used in China, whereas their toxic effect on soil microbial activity remains largely unexplored. In this study, isothermal microcalorimetric technique and soil enzyme assay techniques were employed to investigate the toxic effect of typical sulfide mineral flotation collectors on soil microbial activity. Soil samples were treated with different concentrations (0-100μg•g - 1 soil) of butyl xanthate, butyl dithiophosphate, and sodium diethyldithiocarbamate. Results showed a significant adverse effect of butyl xanthate (p < 0.05), butyl dithiophosphate, and sodium diethyldithiocarbamate (p < 0.01) on soil microbial activity. The growth rate constants k decreased along with the increase of flotation collectors concentration from 20.0 to 100.0μg•g(-1). However, the adverse effects of these three floatation collectors showed significant difference. The IC 20 of the investigated flotation reagents followed such an order: IC 20 (butyl xanthate) > IC 20 (sodium diethyldithiocarbamate) > IC 20 (butyl dithiophosphate) with their respective inhibitory concentration as 47.03, 38.36, and 33.34μg•g(-1). Besides, soil enzyme activities revealed that these three flotation collectors had an obvious effect on fluorescein diacetate hydrolysis (FDA) enzyme and catalase (CAT) enzyme. The proposed methods can provide meaningful toxicological information of flotation reagents to soil microbes in the view of metabolism and biochemistry, which are consistent and correlated to each other.

Effect of adsorption of butyl xanthate on galena, PbS, and HOPG surfaces as studied by atomic force microscopy and spectroscopy and XPS

Atomic force microscopy (AFM) and force spectroscopy techniques have emerged as powerful tools for in situ studies of interactions between solid surfaces, reactants and air bubbles which are of fundamental importance for understanding the mechanisms and increasing the efficiency of froth flotation. Such studies, however, have very rarely involved real mineral sulfides and flotation collectors to date. Here, the tapping mode AFM, force spectroscopy with conventional silicon cantilevers, and ex situ XPS were used to characterize surfaces of single crystals of natural PbS and, for comparison, highly oriented pyrolytic graphite (HOPG) in pure water before and after their pre-treatment in 0.1mM and 10mM potassium n-butyl xanthate (KBX) solutions. Submicrometer domains with the height about 3–8nm were observed on the PbS surfaces with chemisorbed xanthate. The force–distance curves measured upon retraction of the tip from PbS and HOPG surfaces pre-treated in KBX solutions revealed the attraction forces, often with two sudden pull-off steps, acting at the separation distances longer than 100nm. We attributed the soft domains to gas nanobubbles; the long-range attraction was explained in terms of the capillary forces induced by a vapor cavity arising between the tip and the hydrophobic substrates upon their disconnection, and coalescence of the cavity with the pre-existing nanobubbles. The role of these phenomena in flotation is briefly discussed.

Integrated assessment for aerobic biodegradability of sulfide mineral flotation collectors

ABSTRACT The biodegradability of flotation collectors has the most important impact on mine environment. Understanding the flotation collectors’ biodegradability is a crucial element in developing an informed strategy for analysing and managing the mine environment. Integrated assessment method including three biodegradability tests namely, BOD5/CODCr ratio test, Static-flasks test and OECD 301B have been established to evaluate the aerobic biodegradability of the sulfide mineral flotation collectors. Consistent conclusions have been obtained through these three biodegradability tests: the aerobic biodegradation of the different sulfide mineral flotation collectors is different, namely, sodium diethyldithiocarbamate is a readily biodegradable collector, and ammonium butyl-dithiophosphate is partially biodegradable. However, n-butyl xanthate and ethylthionocarbamate are considered as poorly biodegradable. Besides, the order of aerobic biodegradability of these collectors is: sodium diethyldithiocarbamate >...

Quantitative structure–biodegradability relationship of sulfide mineral flotation collectors

12 physicochemical and quantum chemical parameters of 7 kinds of sulfide mineral flotation collectors are calculated. On the basis of the experimental data, a QSBR model including parameters, such as E LUMO , μ, TE, (E LUMO − E HOMO ) and (E LUMO − E HOMO ) 2 was established for K b prediction by multiple linear regression. Results showed that the calculated data fitted well with the experimental values, indicating the reliable prediction and good robustness of the developed model, which can be used in K b prediction of analogs. According to analysis of the model, the electrical parameters were the dominant factors affecting the aerobic biodegradability of sulfide mineral flotation collectors. However, the steric parameters and hydrophobic parameters had a small impact on biodegradability of the collectors.

Primary biodegradation of sulfide mineral flotation collectors

The primary aerobic biodegradation of several sulfide mineral flotation collectors has been studied, and the kinetic model of biodegradation is also discussed. The results show that sodium diethyldithiocarbamate, ammonium butyl-dithiophosphate, n-butyl xanthate can be readily biodegraded, their primary biodegradation extent can reach 97.1%, 93.7%, 81.8%, respectively in 8 d. However, ethylthionocarbamate is difficult to be biodegraded, with its primary biodegradation efficiency being only 37.3% in 8 d. The rate constants follow the order of: k sodium diethyldithiocarbamate> k ammonium butyl-dithiophosphate> k n -butyl xanthate> k ethylthionocarbamate. Their aerobic biodegradation kinetics can be accurately described by first order reaction kinetics equations.

Selection of selective collectors for flotation of minerals with similar flotation properties

A computational method for selecting collectors to investigate the flotation separation of minerals using the principle of hard and soft acids and bases (the Pearson principle) is presented with the examples of sulfide and calcium-containing minerals. Calculated data on the absolute hardness and electronegativity of cations of heavy metals (copper, iron, zinc, and lead) and calcium, solid acids, and ionogenic and nonionic collectors, as well as on the charge transfer in a conjugated “acid-base” pair, are presented. Nonionic low-polar compounds are potentially able to additionally increase the distinctions in the structure of the adsorption layer of collectors on the separated minerals. According to the degree of charge transfer in the conjugated acid (metal cation)-base (collector) pair, the calculated results are correlated with experimental results (non-frothing flotation, adsorption, and IR spectroscopy).

Structural and NMR Studies of the Hexameric Copper(I) Complex with N‐n‐butyl‐N′‐ethoxycarbonyl‐thioureate

AbstractThe copper sulfide mineral flotation collector, N‐n‐butyl‐N′‐ethoxycarbonyl‐thiourea (H2bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)]6, have been characterized by single crystal X‐ray diffraction. H2bectu crystallizes in the triclinic space group $\rm P{\bar 1}$ with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) Å, α = 80.528(6), β = 90.173(6), γ = 76.472(7)°. An intramolecular N‐H···O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six‐membered ring in the central core of the molecule with C=O, C=S and C‐N bond lengths in accord with those reported for other N‐alkyl/aryl‐N′‐acyl‐thiourea compounds. [Cu(Hbectu)]6 crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) Å, β = 91.81(2)° as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu6S6 core consisting of two Cu3S3 chair‐shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n‐butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution 1H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.

Selective attachment and spreading of hydroxamic acid–alcohol collector mixtures in phosphate flotation

Efficient flotation with insoluble-in-water liquid collectors is governed by selective attachment and spreading phenomena at mineral surfaces. This paper investigates the spreading of mixtures of hydroxamic acids and alcohols, recently identified and developed as collectors for the selective flotation of phosphate minerals. The spreading of collector drops on surfaces of apatite and the gangue minerals (dolomite and quartz) immersed in water or surfactant solutions was measured using a high-speed video system and the dynamic contact angle was determined from the transient profiles of the collector drops. Surface and interfacial tensions were measured applying the Du Noüy ring method. The dynamic wetting behavior of collector drops was described using the molecular kinetic theory. This analysis indicates that hydroxamic acids increase the interaction between the alcohol solution and the apatite surface, producing a strong collector attachment. Further information regarding spreading characteristics was obtained from studies at a graphite surface used as a model surface to reveal the nature of the hydrophobic/hydrophobic interaction. The spreading resistance was increased by the hydroxamic acid adsorption resulting in a decrease in the rate of spreading. Both theoretical and experimental results show that at the air–water and alcohol–water interfaces hydroxamic acids exhibit unique interfacial characteristics which account for the selective flotation of apatite from quartz.

A SERS spectroelectrochemical investigation of the interaction of butylethoxycarbonylthiourea with copper surfaces

Abstract The interaction of the sulfide mineral flotation collector, n -butylethoxycarbonylthiourea (BECTU), with copper surfaces at pH 9.2 has been investigated by voltammetry and Raman scattering spectroscopy, NMR, Raman and FTIR spectroscopies have been applied to characterise BECTU and its copper(I) compound to provide a basis for interpreting the spectroelectrochemical data. In the copper compound, the organic molecule is bonded to metal atoms through both its sulfur atom and the nitrogen of the NHCO group of BECTU with the release of the proton. Voltammetry showed that the copper compound is formed above approximately −0.4 V and its presence on the surface inhibits oxide formation. Surface enhanced Raman scattering (SERS) spectra from copper electrodes in the presence of BECTU showed that the major surface species was the copper compound at potentials more than or equal to –0.4 V. The SERS spectrum at approximately −0.5 V was significantly different to that observed from for the bulk compound. This spectrum is interpreted in terms of charge transfer chemisorption of BECTU onto copper atoms in the metal surface.

A spectroelectrochemical investigation of the interaction of diisobutyldithiophosphinate with copper, silver and gold surfaces: II. Electrochemistry and Raman spectroscopy

The interaction of the sulphide mineral flotation collector, diisobutyldithiophosphinate (DIBDTPI), with silver, copper, and gold surfaces has been investigated by voltammetry and Raman scattering spectroscopy. Voltammetry showed that DIBDTPI is oxidised to its disulphide on gold whereas the metal-collector compounds are formed on silver and copper. Surface enhanced Raman spectra (SERS) were observed for silver in the presence of DIBDTPI over a wide potential range and demonstrated that charge transfer chemisorption of the collector takes place. At high potentials, Raman spectra from AgDIBDTPI were also detected. No SERS spectra were evident with copper electrodes, but the formation of CuDIBDTPI was confirmed from Raman spectra. Similar results were observed with diethyldithiophosphate on copper, and this indicates that copper metal does not behave in the same manner as copper sulphide minerals with regard to interaction with thiophosphate collectors. At high potentials on gold, Raman spectra were observed from the disulphide and AuDIBDTPI. SERS spectra were also found on gold under laser illumination that were characteristic of the development of layer of sulfur and this is explained in terms of photolysis of DIBDTPI radicals formed as intermediates in the oxidation of DIBDTPI to its disulphide.

A SERS spectroelectrochemical investigation of the interaction of 2-mercaptobenzothiazole with copper, silver and gold surfaces

The interaction of the sulfide mineral flotation collector, 2-mercaptobenzothiazole, with silver, copper and gold surfaces has been investigated by surface enhanced Raman scattering (SERS) spectroscopy. 2-mercaptobenzothiazole, the copper, silver and gold compounds of this species, and the dithiolate, 2,2′-dithiobis(benzothiazole) were characterised by 13C NMR and Raman spectroscopy to provide a basis for identifying surface species. SERS investigations showed that, at pH 4.6 where the solution species is in the protonated form, and at 9.2, where it is present as the ion, adsorption on each metal occurs over a wide potential range. Attachment of the organic compound occurs through bonding between the exocyclic sulfur atom and metal atoms in the surface. X-ray photoelectron spectroscopy confirmed that the adsorbed layer was of monolayer thickness. Adsorption of the protonated 2-mercaptobenzothiazole occurs on copper at pH 4.6 at potentials below that at which charge transfer adsorption commences.