The removal of zinc from liquid streams by electroflotation

The removal of heavy metals from dilute aqueous solutions (in the range of 10⁻⁷–10⁻⁴ mol dm⁻³) is often not acceptable using classical methods, which do not achieve levels in accordance with environmental quality standards. Electroflotation has certain desirable characteristics, compared to dissolved and dispersed air flotation, particularly in regard to the small bubble size distribution of the process. The aim of this work was to develop an electroflotation (EF)/electrocoagulation (EC) cell to study this combined process and the influence of some relevant parameters/variables, such as collector concentration, tension and current density variation, on the removal of zinc from synthetic solutions containing 20 mg l⁻¹ of the metal. A platinum gore (5 mm) anode and stainless steel mesh cathode were used in the electroflotation cell. The work showed that it was possible to remove zinc by electroflotation, 96% removal being achieved using sodium dodecyl sulfate (SDS) as collector in the stoichiometric ratio 1:3, current density of around 8 mA/cm² and an inlet pH of about 7.0.     

Zinc precipitation by heavy-metal tolerant sulfate-reducing bacteria enriched on phosphogypsum as a sulfate source

In the present study, heavy-metal tolerance and precipitation by a mixed culture of sulfate-reducing bacteria (SRB) were evaluated. These bacteria have been enriched during a previous study from a sewage sludge using phosphogypsum as sulfate source. Taking into account that both sulfate and zinc are naturally occurring in phosphogypsum, zinc tolerance of SRB was tested in synthetic media containing 20 mM sulfate and zinc chloride at concentrations ranging from 0 to 200 mg L⁻¹. Zinc tolerance was determined by bacterial growth susceptibility and zinc removal monitoring. Bacterial growth and sulfate reduction were possible between 10 and 150 mg L⁻¹ of initial zinc concentration. Zinc concentrations more than 150 mg L⁻¹ were lethal to SRB. Zinc was removed effectively by SRB to less than 5% from medium containing 150 mg L⁻¹ initial zinc concentrations or less. Energy-dispersive X-ray analysis showed that precipitation of zinc occurred in the form of sulfide. The results presented in this paper have shown that this mixed culture might be of use for bioremediation of sulfate and heavy-metals containing wastewaters.     

Biosorptive removal of Cd and Zn from liquid streams with a Rhodococcus opacus strain

The biosorption abilities of Rhodococcus opacus were studied for cadmium and zinc removal for liquid aqueous streams. The influence of pH, initial metal concentration and time removal were evaluated on the biosorption studies, in a batch scale basis. The Cd²⁺ and Zn²⁺ species uptake capacity by R. opacus has been also compared using Langmuir and Freundlich models. At pH 7.0 and 26 °C C, Cd²⁺ removal achieved a value around 60% from an initial concentration of 15 ppm. On the other hand, Zn removal achieved a value around 88% from an initial concentration of 5 ppm. Kinetics studies revealed that the biosorption process followed a pseudo-second order model for the two metal species (Cd²⁺ and Zn²⁺) and the kinetic constants were 3.90 and 3.37 g mg⁻¹ min⁻¹, for an initial concentration of 15 and 5 ppm for cadmium and zinc, respectively. The results showed that the R. opacus is a potential engineering biosorbent for environmental and extractive metallurgy sustainable applications.     

Simultaneous oxidation and immobilization of arsenite from refinery waste water by thermoacidophilic iron-oxidizing archaeon,Acidianus brierleyi

The use of a thermophilic acidophilic iron-oxidizing archaeon, Acidianus brierleyi, was investigated for oxidation and immobilization of As(III) from acidic refinery waste water. Some As(III) oxidation was measured in all Ac. brierleyi cultures independently of the presence or concentration of Fe(II) in bulk solution; the exception was at initial Fe(II) concentration ([Fe(II)]_ini) of 1000 mg l⁻¹ where As(III) oxidation became markedly facilitated and consequently approximately 70% of As was immobilized as amorphous ferric arsenate. Providing 1000 mg l⁻¹ Fe(III) instead of Fe(II) did not show the same effect, implying the importance of Fe(III) be microbially-produced and complexed in the archaeal EPS (extracellular polymeric substances) region for effective As(III) oxidation. The reaction towards secondary mineral formation shifted from ferric arsenate to jarosite at [Fe(II)]_ini of >1000 mg l⁻¹. Furthermore addition of jarosite seed crystals retarded the As(III) oxidation rate at [Fe(II)]_ini of 1000 mg l⁻¹. The observations indicate that by setting the appropriate bulk Fe(II)/As(III) ratio in Ac. brierleyi culture to achieve a certain concentration of Fe(III) within the EPS region, but at the same time to avoid jarosite formation, it is possible to maximize the As(III) oxidation rate and thus As immobilization efficiency. This study describes for the first time microbially-mediated simultaneous oxidation and immobilization of As(III) as ferric arsenate, using a thermoacidophilic iron-oxidizing archaeon, Ac. brierleyi.     

Simultaneous determination of iron and copper in pregnant liquid solutions

A new method for the determination of Fe_Total and Cu is proposed. The method is based on the formation of the iron and copper complexes with 5-sulfosalicylic acid (SSA), the optimal conditions were found, using SSA 5.1 g L⁻¹ in the presence of ammonia 7.5 g L⁻¹ (pH = 10). Under these conditions the selected analytical wavelengths were 488.5 and 423.5 nm for the determination of iron and copper, respectively, by using the zero crossing approach. The detection and quantification limits were 0.02 mg L⁻¹ and 0.07 mg L⁻¹ for iron and 1.14 mg L⁻¹ and 3.80 mg L⁻¹ for copper. The proposed method was applied to the determination of both analytes in pregnant liquid solutions and the recovery was between 98% and 100% and in all cases the relative standard deviation was minor to 2%.     

Adsorbing flocs in expanded/fluidised bed reactors: A new basis for pollutants removal

The present work describes studies concerning a new adsorption technique based on the use of adsorbent flocs in an expanded/fluidised bed reactor for the removal of pollutants from aqueous solutions. The technique, based on flocculation of aqueous suspensions of powdered adsorbent materials, when conducted in an expanded/fluidised bed reactor takes advantage of conducting adsorption and solid–liquid separation in one single stage. Studies were performed using flocculated powdered activated carbon and natural zeolites, alone and in mixtures, for phenol and ammonia adsorption. A reactor with cylindrical–conical geometry was used for the pollutants adsorption in flocs beds (pure and mixed), as well as the regeneration/recycle of the exhausted adsorbents. Results proved the high adsorption efficiency of powdered natural zeolites and activated carbon flocs for the uptake of ammonia (11 mg NH₃–N g⁻¹) and phenol (132 mg g⁻¹), at 38 and 19 m h⁻¹ loading rates, respectively. Regeneration/recycle of the pollutant-saturated beds was possible for the ammonia/natural zeolites adsorption case, using sodium sulphate as regenerator. Use of mixed flocs beds was efficient, showing advantages such as multiple-pollutants adsorption in one single stage, higher loading rates when using light materials (activated carbon) combined with heavier ones (natural zeolites) and use of small adsorbent concentrations (not possible otherwise). Economical and environmental issues regarding the technique are also discussed in the paper. The new technique shows great potential as an alternative physicochemical adsorption process for pollutant removal from aqueous solutions using low-cost and highly-available powdered adsorbent materials.     

Selective flotation of cassiterite with benzohydroxamic acid

The flotation of cassiterite mineral from gangue with a collector benzohydroxamic acid (BHA), and the interactions between the BHA and cassiterite have been investigated. It is shown through microflotation that the BHA is able to flot cassiterite very well, calcite quite limitedly, and quartz not at all, so the selective separation of cassiterite–quartz mixture was readily achieved; while for the efficient separation of cassiterite–calcite mixture containing 48.94% SnO₂, sodium hexametaphosphate (SHMP) was needed as a depressant for the gangue, and under the condition of the BHA 100 mg L⁻¹, SHMP 3.5 mg L⁻¹, a cassiterite concentrate with the grade of 85.50% SnO₂ was obtained with the recovery of SnO₂ 95.5%. Batch flotation further demonstrated that for an industrial tin slime, which contained 0.42% Sn, 13.65% SiO₂, 24.14% CaO, 16.60% MgO, 4.50% Al₂O₃ and 6.58% Fe, the tin recovery of 84.5% after one separation was reached with the concentrate grade of 1.84% Sn under the condition of the BHA 178 mg L⁻¹, SHMP 27 mg L⁻¹. In terms of zeta potential and infrared spectra studies the main interactions between the collector BHA and the mineral cassiterite in a flotation system are chemisorption with the formation of Sn–BHA compounds rather than electrostatic attractions between them.     

Sulphate and molybdate ions uptake by chitin-based shrimp shells

The removal of sulphate and molybdate anions (among other anions) from mining liquid effluents is attracting much interest because of the strict environmental legislation world-wide and the need for water recycling and reuse. In this work, adsorption of sulphate and molybdate ions on chitin-based materials was investigated. Chitin flakes with various deacetylation degrees (DD) were produced from an industrial shrimp shell waste after demineralisation, deproteinisation and deacetylation steps, without further purification, immobilisation or grinding. Batch adsorption experiments were carried out as a function of pH and the best adsorbent material was selected following its chemical stability in acidic medium, degree of anions uptake and time needed for the deacetylation reaction stage. Thus, detailed sulphate adsorption studies were conducted with a chitin having a 25% DD, at various adsorbent concentrations, medium pH and other operating conditions. Best sulphate removal values (92%) were obtained at equilibrium pH 4.5, 8.5 mg mg⁻¹ chitin/ions ratio and 15 min contact time. The adsorption data followed the Langmuir model and showed saturation values of the order of 3.2 mEq g⁻¹. Chitin also proved to adsorb molybdate ions in the presence of sulphate ions, but reaction required longer equilibration time (60 min for the same 92% removal). Practical examples of removal of these anions were studied in actual mining effluents, attaining values of the order of 71% sulphate and 85% Mo from a Cu–Mo flotation mill effluent and 80% sulphate removal from a coal AMD––acid mines drainage (Mo free). The regeneration of the adsorbent material was possible through the anions desorption in alkaline medium. All results are discussed in terms of solution and interfacial phenomena and the practical aspects of the process, in the mining and metallurgy fields, are envisaged.     

Review of rate constants for thiosulphate leaching of gold from ores,concentrates and flat surfaces: Effect of host minerals and pH

A review of literature data for different types of sulphide concentrates and gold ores has been carried out to examine the impact of host minerals and pH upon gold leaching. Analysis of initial rate data over the first 30–60 min of gold leaching from sulphide concentrates or silicate ores over a range of ammonia, thiosulphate, and copper(II) concentrations, pH (9–10.5) and temperatures up to 70 °C shows the applicability of a shrinking sphere kinetic model with an apparent rate constant of the order k_ss = 10⁻⁶–10⁻³ s⁻¹. The dependence of apparent rate constant on pH and initial concentrations of copper(II) and thiosulphate is used to determine a rate constant k_Au(ρr)⁻¹ of the order 1.0 × 10⁻⁴–7.4 × 10⁻⁴ s⁻¹ for the leaching of gold over the temperature range 25–50 °C (ρ = molar density of gold, r = particle radius). These values are in reasonable agreement with rate constants based on electrochemical and chemical dissolution of flat gold surfaces: k_Au = 1.7 × 10⁻⁴–4.2 × 10⁻⁴ mol m⁻² s⁻¹ over the temperature range 25–30 °C. The discrepancies reflect differences in surface roughness, particle size and the effect of host minerals.     

Oxidation of cyanide in effluents by Caro’s Acid

Caro’s Acid (peroxymonosulphuric acid: H₂SO₅) is a powerful liquid oxidant made from hydrogen peroxide that has been adopted for the detoxification of effluents containing cyanides in gold extraction plants in recent years.The present work reports the findings of a study on the kinetics of aqueous cyanide oxidation with Caro’s Acid. Experiments were conducted in batch mode using synthetic solutions of free cyanide. The experimental methodology employed involved a sequence of two 2³ factorial designs using three factors: initial [CN⁻]: 100–400 mg/L; H₂SO₅:CN⁻ molar ratio: 1–1.5–3–4.5; pH: 9–11; each one conducted at one level of Caro’s Acid strength which is obtained with the H₂SO₄:H₂O₂ molar ratio used in Caro’s Acid preparation of 3:1 and 1:1. The objective was the evaluation of the effect of those factors on the reaction kinetics at room temperature. Statistical analysis showed that the three investigated variables were found to be significant, with the variables which affected the most being the initial [CN⁻] and the H₂SO₅:CN⁻ molar ratio. The highest reaction rates were obtained for the following conditions: H₂SO₅:CN⁻ molar ratio = 4.5:1; pH = 9; and Caro’s Acid strength produced from the mixture of 3 mol of H₂SO₄ with 1 mol of H₂O₂. These conditions led to a reduction of [CN⁻] from an initial value of 400 mg/L to [CN⁻] = 1.0 mg/L after 10 min of batch reaction time at room temperature. An empirical kinetic model incorporating the weight of the contributions and the interrelation of the relevant process variables has been derived as: −d[CN⁻]/dt = k [CN⁻]^1.8 [H₂SO₅]^1.1 [H⁺]^0.06, with k = 3.8 (±2.7) × 10⁻⁶ L/mg min, at 25 °C.     

Single and binary component sorption of the fission products Sr2+, Cs+ and Co2+ from aqueous solutions onto sulphate reducing bacteria

This study investigates the removal of the fission products Sr²⁺, Cs⁺ and Co²⁺ in single and binary metal solutions by a sulphate reducing bacteria (SRB) biomass. The effect of initial concentration and pH on the sorption kinetics of each metal was evaluated in single metal solutions. Binary component equilibrium sorption studies were performed to investigate the competitive binding behaviour of each metal in the presence of a secondary metal ion. Results obtained from single metal equilibrium sorption studies indicated that SRB have a higher binding capacity for Sr²⁺ (q_max = 416.7 mg g^?1), followed by Cs⁺ (q_max = 238.1 mg g^?1), and lastly Co²⁺ (q_max = 204.1 mg g^?1). Among the binary systems investigated, Co²⁺ uptake was the most sensitive, resulting in a 76% reduction of the sorption capacity (q_max) in the presence of Cs⁺. These findings are significant for future development of effective biological processes for radioactive waste management under realistic conditions.     

Impact of organic carbon on the leachability of vanadium,manganese, iron and molybdenum from shale residues

From 1942 to the 1966, oil was produced by pyrolysis of shale, in Kvarntorp, Sweden. This generated some 40 million m³ of metal rich pyrolyzed shale and discarded fines that were piled on site with its original metal content almost intact. The present study focuses on the leaching of vanadium, manganese, iron and molybdenum from fines after addition of wood chips and steel slag, in outdoor 1 m³ reactor systems at low liquid to solid ratio, in order to evaluate the potential environmental impact and recovery of the elements from the leachates. Seasonal variations were observed, with increased leaching during peak summer. For vanadium and molybdenum, high addition of wood chips decreased the leaching, probably due to adsorption. Manganese showed the opposite behavior while leaching of iron was almost independent of the amount of wood chips. Depending on the systems, up to 2200 μg L⁻¹ vanadium, 90 μg L⁻¹ molybdenum, 25 mg L⁻¹ manganese and 500 mg L⁻¹ iron was found in the aqueous phase. Applied to the 40 million m³ pile, the annual leaching of those elements may reach 14 ton, 0.6 ton, 200 ton and 2400 ton, respectively.     

The reduction of chromite in the presence of silica flux

The mechanism and kinetics of the carbothermic reduction of a natural chromite was studied at 1300–1500 °C in the presence of silica. Thermogravimetry, X-ray diffraction (XRD) analysis, energy dispersive X-ray analysis (EDAX) and metallography were the experimental techniques used. Silica affected the reduction at and above 1400 °C. A two stage reduction mechanism was established. The first stage, up to about 40% reduction, is primarily limited to iron metallization and zoning is observed in partially reduced chromites. In this stage silica does not interfere with the reduction. The second stage is mainly confined to chromium metallization and formation of a silicate slag alters the reduction mechanism. Ion-exchange reactions between the reducible cations (Cr³⁺ and Fe²⁺) in the spinel and the dissolved cations (A1³⁺ and Mg²⁺) in the slag allow further reduction. Due to the very high driving force for the diffusion, the overall process is shifted toward a more chemical reaction controlled mechanism. A generalized rate equation was then applied to the individual metallization curves of iron and chromium from which respective rate constants and diffusion coefficients were derived. The rate constants were in the range 6.74 × 10⁻⁴–9.01 × 10⁻⁴ s⁻¹ for iron and 7.20 × 10⁻⁴–8.50 × 10⁻⁴ s⁻¹ for chromium reduction at 1500 °C in the presence of silica. At 1500 °C, the corresponding diffusion coefficients were in the range 3.14 × 10⁻⁸–4.78 × 10⁻⁸ m²/s for Fe²⁺ diffusion in the spinel and in the range 1.70 × 10⁻⁸–2.03 × 10⁻⁸ m²/s for the respective diffusion of Cr³⁺. Finally using Arrhenius plots activation energies were derived.     

Application of ocean manganese nodules for the adsorption of potassium ions from seawater

Extracting potassium from seawater has great economic potential, although conventional methods offer low separation capacity and selectivity. In this study, a series of novel potassium ionic sieves (PISs) were synthesized using ocean manganese nodules (OMN) as raw materials. The PISs were characterized by XRD, SEM, and nitrogen adsorption–desorption. The potassium adsorption capacities and separation factors of PISs and OMN in KCl solution and sea brine showed that KMnO₄ treatment will result in the highest adsorption and separation performance. The resulted sample OMN-C exhibit major composition of birnessite-type potassium manganese oxides and high micropore volumes. The adsorption capacities of OMN-C to K⁺ in KCl solution and sea brine were 35.2 mg g⁻¹ and 22.1 mg g⁻¹, respectively. The separation factor of OMN-C was α(K⁺/Na⁺) = 108.6 and the sieve did not adsorb Mg²⁺, indicating its relatively high separation selectivity to K⁺. Therefore, OMN-C can selectively extract potassium from sea brine effectively. This study not only utilized the abundant OMN resources, but also prepared effective PISs, which showed great potential in the utilization of seawater.     

Multicolumn solid phase extraction with hybrid adsorbent and rapid determination of Au,Pd and Pt in geological samples by GF-AAS

A novel hybrid adsorbent (HA) composed of cellulose fiber, activated carbon, and anion exchange resin Dowex 1 × 8 was prepared for the preconcentration and separation of noble metals, namely, gold (Au), palladium (Pd) and platinum (Pt), in geological samples. The optimal experimental parameters, such as flow rate, sample volume and interfering ions, were investigated. The accuracy of the method was confirmed by added/found method for tap and sea water, and evaluated by analyzing certified reference materials with good agreement. Under the optimal experimental conditions, the detection limits (3σ criteria) of the developed technique were 0.008 ng mL⁻¹ (Au), 0.017 ng mL⁻¹ (Pd) and 0.014 ng mL⁻¹ (Pt) and the sample throughput reach to 30 samples every eight hours. Moreover, the adsorption capacity of HA for Au, Pd and Pt was determined to be 48.2, 35.9 and 29.8 mg g⁻¹, respectively.     

Evaluation of the ASTERTM process in the presence of suspended solids

The ability to recycle and reuse process water is a major contributing factor toward increased sustainability in the mining industry. However, the presence of toxic compounds has prevented this in most bioleaching operations. The ASTER^TM process has been used for the bioremediation of cyanide (CN) and thiocyanate (SCN⁻) containing effluents at demonstration and commercial scale, increasing the potential for recycling of the treated effluent. The process relies on a complex consortium of microorganisms and laboratory tests have shown that the biomass retention, in suspended flocs or attached biofilm, significantly improved SCN⁻ degradation rates. The current research evaluated the process performance in the presence of suspended solids (up to 5.5% m/v) ahead of implementation at a site where complete tailings removal is not possible. Experiments were performed in four 1 l CSTRs (with three primary reactors in parallel at an 8 h residence time, feeding one secondary reactor at a 2.7 h residence time). Stable operation at the design specifications (5.5% solids, 100 mg/l SCN⁻ feed, effluent SCN⁻ <1 mg/l) was achieved within 50 days, including a period of adaptation. The pH had the most significant effect on performance, with significant inhibition below pH 6. The presence of gypsum and anhydrite phases in the fresh tailings was most likely responsible for the observed decrease in pH. A maximum SCN⁻ degradation rate of >57 mg/l/h was achieved, despite no obvious floc formation. Microbial ecology studies (16S rRNA clone library) revealed reduced diversity relative to reactors operated without suspended solids.     

Aqueous dispersions of nanobubbles: Generation,properties and features

Nanobubbles (NBs) have interesting and peculiar properties such as high stability, longevity and high surface area per volume, leading to important applications in mining-metallurgy and environmental areas. NBs are also of interest in interfacial phenomena studies involving long-range hydrophobic attraction, microfluidics, and adsorption at hydrophobic surfaces. However, little data are available on effective generation of concentrated NBs water dispersions and on their physicochemical and interfacial properties. In this work, air was dissolved into water at pH 7 and different pressures, and a flow was depressurized through a needle valve to generate 150–200 nm (mean diameter) NBs and MBs-microbubbles (about 70 μm). Microphotographs of the NBs were taken only in the presence of blue methylene dye as the contrast medium. Main results showed that a high concentration of NBs (number per volume) was obtained by decreasing the saturation pressure and surface tension. The number of NBs, at 2.5 bar, increased from 1.0 × 10⁸ NB mL⁻¹ at 72.5 mN m⁻¹ to 1.6 × 10⁹ NB mL⁻¹ at 49 mN m⁻¹ (100 mg L⁻¹ α-Terpineol). The NBs mean diameter and concentration only slightly varied within 14 days, which demonstrates the high stability of these highly concentrated NBs aqueous dispersions. Finally, after the NBs were attached to the surface of a grain of pyrite (fairly hydrophobic mineral), the NBs dramatically increased the population of MBs, which shows the enhancement of particle hydrophobicity due to NBs adhesion. The results were explained in terms of interfacial phenomena and it is believed that these tiny bubbles, dispersed in water at high concentrations, will lead to cleaner and more sustainable mineral flotation.     

Effect of fluidized-bed carrier material on biological ferric sulphate generation

High biomass hold-up and high iron oxidation rates of a biological ferric sulphate generating fluidized-bed reactor (FBR) requires a carrier material with high specific surface area, high porosity and inertness. In this work, the effect of activated carbon (AC), diatomaceous earth (Celite) and Al₂O₃ (Compalox) carrier materials on the ferric sulphate generation in FBRs were studied. Compalox dissolved during the experiments and formed an unfluidizable aggregate, and was therefore rejected. The slow dissolution of Celite resulted in a light, fine-grained, layer on top of the fluidized bed that had to be changed into fresh Celite. AC resisted well the friction caused by fluidization. The iron oxidation in the continuous-flow FBRs became limited by oxygen supply already at loading rates of 2.5 kg Fe²⁺ m⁻³ h⁻¹. Iron oxidation rates of 27.6 and 25.7 kg m⁻³ h⁻¹ were obtained in batch FBR experiments with AC and Celite, respectively.Biomass accumulation of 6.2 × 10¹⁰, 2.4 × 10¹⁰ and 8.0 × 10⁹ cells per g of carrier was detected on Celite, AC and Compalox, respectively. The bacterial community structures on the carrier materials were revealed by Polymerase Chain Reaction and Denaturating Gradient Gel Electrophoresis (PCR-DGGE) followed by partial sequencing of the 16S rRNA gene. Two bacterial strains, Leptospirillum ferriphilum and a strain similar to a strain unofficially named “Ferrimicrobium acidiphilum”, were detected. Examination of the carrier material surfaces with scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) revealed that all carrier materials were covered with jarosite precipitates and that the bacteria were mainly retained on the jarosite covered areas. In conclusion, AC was the most promising carrier material for a large-scale biological ferric sulphate generating FBR based on its availability, durability and the achieved high iron oxidation rates.     

Density functional theory study of α-Bromolauric acid adsorption on the α-quartz (1 0 1) surface

Adsorption mechanism of collector α-Bromolauric acid (CH₃(CH₂)₉CHBrCOOH, α-BLA) on α-quartz (1 0 1) surface has been investigated by first-principles calculations based on density functional theory (DFT). The interaction energies of H₂O molecule, calcium ions (Ca²⁺), hydroxyl ions (OH⁻), calcium hydroxyl ions (Ca(OH)⁺), and α-BLA⁻ ions with α-quartz (1 0 1) surface were in the order of Ca(OH)⁺ < Ca²⁺ < OH⁻ < H₂O < α-BLA⁻. The results revealed that the collector α-BLA cannot adsorb on α-quartz (1 0 1) surface due to the hindrance of hydration shell of quartz surface, while Ca(OH)⁺ could repulse the hydration shell and consequently adsorb on quartz surface, which further leads to the adsorption of the collector α-BLA⁻ anions on Ca(OH)⁺-activated quartz surface. Mulliken populations analysis of the external oxygen atom (O2) of quartz surface, calcium atom (Ca) of Ca(OH)⁺, and oxygen atom (O1) of collector α-BLA⁻ (–OH group) shows that the electron transfer between the Ca–O1 and Ca–O2 atoms. The overlap area of electron density between Ca–O1 and Ca–O2 atoms indicates strong interactions among the three atoms of Ca, O1, and O2, suggesting that Ca(OH)⁺ ions act as a bridge between the α-quartz (1 0 1) surface and the α-BLA collector.