High Alkali Content Research Articles

Petrology and geochemistry of Late Triassic rapakivi-type granites in the Dupangling area, South China: Role of fluid-rock interaction in the origin of rapakivi texture

Rapakivi-type granites not only document magmatic processes but also archive subsolidus interactions between granitic rock and fluid, and thereby provide crucial information about fluid infiltration in the Earth's crust. However, the key process to generate rapakivi texture is still debated. Here, we report comprehensive mineralogical, geochemical and Hf isotopic compositions of the Dupangling rapakivi granites (210.4–214.9 Ma) in the South China Block to investigate the effect of fluid-rock interaction on the origin of rapakivi feldspar. Dupangling rapakivi granites have high SiO2 (72.63–78.21 wt%) and alkali contents (Na2O + K2O = 6.14–9.06 wt%) with high K2O/Na2O ratios (1.37–2.64), characteristic of weakly peraluminous (A/CNK = 1.04–1.10) high-K calc-alkaline granites. Samples have weakly fractionated REE patterns with negative Eu anomalies (δEu = 0.05–0.38). They have negative whole-rock εNd(t) (−8.45 to −7.91), variable zircon εHf(t) (−9.7 to −1.0) and two-stage Hf isotope model ages (1.32–1.84 Ga), due to their derivation from a major early Mesoproterozoic crustal source with a subordinate late Paleoproterozoic component. Rapakivi feldspars in Dupangling granites are composed of an alkali-feldspar core and a plagioclase mantle. Fractures, pores and secondary inclusions (biotite, sericite, epidote and hematite) are closely associated with the mantles and oligoclase patches within alkali-feldspar cores. These pervasive microtextural features and variations of Be, Rb, Ba, Sr and LREE within rapakivi feldspars are interpreted to have formed through subsolidus fluid-induced dissolution-reprecipitation replacement processes. This study highlights that fluid-rock interaction plays an important role in generating rapakivi texture.

Local high concentration alkali field accelerated silicon hydrolysis for hydrogen production

Silicon is considered as a promising portable hydrolytic hydrogen production material due to its abundant raw materials, high theoretical capacity (1600 mL/g) and facile storage. However, the low hydrolysis activity and slow hydrolysis rate of silicon hinder its practical application. To address this issue, we introduced CaH2 to form Si-based composites via a flexible ball milling method. The above composites showed ideal yield (1216 mL/g in 10 min), reaction conversion (95.5%) and fast hydrolysis kinetics (225 mL/(s·g)) in deionized water, which is one of the best hydrolysis performances of Si-based composites so far. The hydrolytic process can be divided into two steps: the splitting hydrolysis of CaH2 and the continuous hydrolysis of Si. Combining the dynamic in-situ structural analysis with the analogue simulation, it can be confirmed that the formation of local high concentration alkali field is the key to promote the complete hydrolysis and achieve high yield and fast kinetics of the composites. The existence of lattice defects was proved and the adsorption of Si to hydroxide ion was proved by theoretical calculation. Our work provided a novel idea for the theoretical design of hydrolytic hydrogen production compounds and promoted the practical application of low cost and portable hydrolytic hydrogen production materials.

Experimental study on the potential application of biomimetic mineralized composites based on BCICP

A biomimetic-chemically induced carbonate precipitation method (BCICP) using boric acid as a crystal modifier is proposed to develop new cementing material. This study further explored the potential application of biomimetic mineralized composites using the BCICP method in different environments, including particle size, alkaline conditions, and sand mineralogy. The results show that as the particle size increases, the UCS value decreases by 1.52 MPa, and the compressive strength of biomimetic mineralized composites with multi-graded (0.1–1.0 mm) is significantly better than that with single-graded (0.1–0.2 mm). Moreover, the effect of alkaline sand depends on the alkali content, and the low alkali level is beneficial for cementation with a maximum UCS of 1.68 MPa. However, high alkali content would consume boric acid, resulting in poor pore filling and significantly reducing strengthening efficiency. In addition, BCICP also has a higher strengthening cementing efficiency for sand with copper oxide and calcium carbonate as the main minerals, and the UCS increases by 16.2% and 57.3% compared to Toyoura sand, respectively. The findings of this study provide insights into future design and applications of biomimetic mineralized composites.

Analysis of Alkali in Bayer Red Mud: Content and Occurrence State in Different Structures

The application of large amounts of red mud in the field of building materials is one of the main ways to reuse this material, but the high alkali content of red mud limits its application. In this paper, the washable alkali, removable alkali, and lattice alkali contents of Bayer red mud were studied, and the occurrence states of potassium and sodium in red mud were studied using XRD, IR, XPS, and NMR. On this basis, the removal mechanism for potassium and sodium in red mud was analyzed. The results showed that the Na in the red mud was mainly deposited in the shelf silicon voids of hydroxy sodalite (Na8(AlSiO4)6(OH)2(H2O)2) in the form of Si-O-Na or Al-O-Na. K is deposited in the shelf silico-oxygen void of potassium feldspar (KAlSi3O8) in the form of Si-O-K or Al-O-K. The washable Na and K contents of the mud were 13.7% and 4.47%; the alkali removal agent CaO removed 83.1% and 50.8% of Na and K in the red mud; and the lattice alkali Na and K contents were 3.20% and 44.8%, respectively. In the process of red mud dealkalization, Ca2+ ions can enter the internal voids of the hydroxyl sodalite and potassium feldspar silica skeleton and then replace Al3+ in the Si-O skeleton and Na+ and K+ in the skeleton voids. The replacement reaction changes the silica tetrahedron network structure, resulting in the disintegration of the frame-like silica tetrahedron in the hydroxyl sodalite and potassium feldspar, forming an isolated, island-like silica tetrahedron in hydrated garnet.

Revisiting the carbonation of recycled concrete fine: A pH-cycle carbonation method

Recycled concrete fine (RCF) has been demonstrated as a promising CO2 absorbent owing to its high-calcium and high-alkali contents. For the high-efficiency utilization of bubbled CO2 for the carbonation of RCF, this paper revisits the carbonation process by proposing a pH-cycle carbonation method. The carbonation of RCF was suspended when the pH of RCF suspension dropped to 7, and the subsequent carbonation was started when the pH reached constant values. The effect of the pH-cycle carbonation method on the performance of RCF-added mortars was investigated by preparing mortars using RCF suspension with different carbonation cycles. Experimental results showed that RCF spontaneously dissolved and released Ca2+ to the suspension during the intervals of carbonation cycles, which could save some CO2 that should be spent on attacking RCF in continuous carbonation approaches. In this method, the CO2 sequestration potential of RCF is approaching depletion by the bubble of 7 min CO2. The carbonation of RCF enabled the formation of CaCO3 crystals and nano-silica, leading to accelerated hydration of cement and refined pore structure of RCF-added mortars. The 28d compressive strength of RCF-added mortars was increased by 10.27–12.57% when RCF was subjected to different carbonation cycles. The two cycles of carbonation for RCF could be the optimal one.

Alkali fusion of bauxite refining residue (red mud-RM) to produce low carbon cements

This paper creates hydraulic binders using waste and a low energy input. Cements are produced with a bauxite refining residue (red mud-RM), blended with limestone and lime, and fused at temperatures from 600 to 1200 °C. The Saudi RM investigated has significant Al and Si but low Ca. Therefore, lime (CaO) and limestone (CaCO3) are used, as a source of calcium, to harvest cementing hydrates.When calcining RM alone, reactive aluminium phases begin to form at c.300 °C. However, at c.900 °C, they turn into crystalline corundum (Al2O3), a more stable and less reactive phase. It is hoped that the Ca provided by the lime/limestone will react with the Al in the RM during fusion, to form reactive silicates and aluminates rather than inert corundum. Both types of fusion produced calcium silicates and aluminates with cementing properties. However, lime fusion required higher temperature. Limestone fusion produces cementing phases at lower temperature than lime fusion, due to the lower decomposition temperature of CaCO3 when compared to CaO. High temperature is required to break down CaO (melting point = 2572 °C), whereas CaCO3 decomposes at 600 °C and disappears at 850 °C. Despite the top alkali fusion temperature being much lower than the CaO melting point, the results demonstrate that calcium was released from the lime and entered reactions forming calcium silicates and aluminates. This is probably due to the high alkali content of the RM acting as a flux and lowering the decomposition temperature of the CaO.

Formation conditions of andesites of Sulawesi Island (Indonesia)

Research subject. Andesitic complexes of the Tondono caldera and Lokon-Empung volcano locate din the northeastern part of the Sulawesi Island (Indonesia).Aim. To determine the petrogenesis conditions of andesites in the northeast Sulawesi Island based on detailed studies of volcanic rocks of the Tondono caldera and Lokon-Empung volcano.Materials and methods. We studied volcanic rock samples collected by I.Yu. Safonova. To determine the petrogenesis conditions of andesites, conventional petrochemical, geochemical and mineralogical methods were used. Melt inclusions were also studied using a MIRA 3 LMU scanning microscope equipped with Aztec Energy XMax 80 system of microanalysis, and a Horiba LabRam HR800 Raman spectroscope. The PT-parameters of crystallization were estimated from the data on the composition of melt inclusions using approaches reported by K.D. Putirka, F. Yavuz and D.K. Yıldırım.Results. The Sulawesi andesites represent tholeiitic and calc-alkaline island-arc magmas. Pyroxenes phenocrysts crystallized from melts that evolved with accumulation of alkalis and silica. Plagioclase phenocrysts crystallized from the felsic magmas, which are characterized by a decreasing role of alkalis. The composition of volcanic glass of the mesostasis suggests participation of felsic melts with a very high content of alkalis. The compositions of minerals and glasses in inclusions and in the mesostasis allowed us to estimate PT-parameters of the petrogenesis of the andesites. The phenocrysts of pyroxene crystallized in two intermediate magma chambers at depths of 27.6–14.6 and 11.3–7.2 km and temperatures ranging from 1150 to 970ºС. The phenocrysts of plagioclase crystallized at 930–910 and 900–890ºС. The microcrystals (laths) of plagioclase in the mesostasis crystallized at lower temperatures of 875–865 and 840–810ºС.Conclusions. The andesites of the Sulawesi Island were derived from tholeiitic to calc-alkaline melts compositionally similar boninites. The compositions of the glasses in melt inclusions and mesostasis showed three types of compositionally different parental magmas, which produced the Sulawesi andesites. The phenocrysts of pyroxenes crystallized from these melts in two magma chambers at depths of 27.6 to 7.2 km and at temperatures of 1150 to 970ºС. The phenocrysts and laths of plagioclase crystallized at lower temperatures of 930 to 810ºС.

Geochronology, petrogenesis, and mineralization potential of the syenogranites in the Yama fluorite deposit, Tataleng granitic batholith, Qilian Orogen, NW China

The Yama fluorite deposit in the Qilian Orogen in NW China is characterized by predominant granitic magmatism and fluorite mineralization. The wall rocks hosting the fluorite–quartz veins in the Yama area consist of the Yama porphyritic syenogranite and the Wulandawu syenogranite. In this study, the major and trace element compositions, zircon U–Pb ages, and zircon Hf isotopes and trace element compositions were investigated. Two samples for the Yama porphyritic syenogranite yielded weighted mean 206Pb/238U zircon ages of 440.7 ± 4.8 and 447.9 ± 6.0 Ma, and one sample for the Wulandawu syenogranite yielded a weighted mean 206Pb/238U zircon age of 441.2 ± 5.0 Ma, all of which indicate a Late Ordovician to Early Silurian crystallization age. Geochemically, both syenogranites are peraluminous, with high alkali contents, low Zr + Nb + Ce + Y contents, relatively low (K2O + Na2O)/CaO ratios, and high Rb/Sr and Rb/Ba ratios, suggesting that they are fractionated S-type granites. They have zircon εHf( t) values of −14.9 to −4.4 and −12.2 to −4.5, respectively, suggesting that they were derived from the partial melting of pelitic-rich sources within the relatively shallow Paleoproterozoic reworked crust. The detailed geochronological and geochemical data suggest that the studied syenogranites were emplaced in a post-collisional setting related to the closure of the South Qilian Ocean. Finally, they have relatively low quantitative oxygen fugacity values, indicating relatively reduced redox states, but their very low zircon Ce4+/Ce3+ ratios, low whole-rock K/Rb ratios, relatively high Nb/Ta ratios, and low Zr/Hf ratios suggest that they are not likely to form important W–Sn deposits and related fluorite deposits.

Revealing the link between A-type granites and hottest melts from residual metasedimentary crust

Abstract Among S-, I-, and A-type granites, the latter are the most debated in terms of origin, and metasedimentary crust is usually discarded as a potential source. Here we tackle this issue by adopting an in-source perspective, rather than focusing on the final product (granite), documenting the occurrence of pristine melt inclusions (MIs) in garnet from residual metapelitic ultrahigh-temperature (UHT) granulite from East Antarctica. Coexistence of sapphirine + quartz, phase equilibria calculations, and Zr-in-rutile thermometry indicate that MIs trapped UHT melts formed at peak conditions (930–1000 °C) from a residual metapelitic source. MIs are granitic with weakly peraluminous to weakly peralkaline affinity, ferroan character, high alkali contents, high K/Na and Ga/Al, and low Ca, Ba, Sr, and H2O concentrations. These features and geochemical modeling indicate that MIs represent primary melts for high-SiO2 A-type granites. Therefore, MIs reveal the missing link between A-type granites and the hottest metasedimentary crust. Voluminous amounts of slightly peraluminous, high-SiO2 A-type granites can be produced in large, residual UHT terranes such as those of eastern Gondwana. Our results provide a wider view of processes responsible for granite formation and show that a larger variety of granites must be considered in models of the effects of UHT anatexis on crustal differentiation.

Ab-initio calculations on the interaction between OH− and Fe2Mo Laves phase

In the process of heat treatment at high temperature, A2B type intermetallic compound Fe2Mo can precipitate out in the martensitic heat-resistant steel. When the martensitic heat-resistant steel is used in high concentration alkali solution of 7 mol/L, the Fe2Mo Laves phase can dissolve. Meantime, the dissolution behaviors of different shapes of Fe2Mo Laves phase are also distinct. However, there is still no effective micro-mechanism to explain the dissolution behaviors of Fe2Mo Laves phase. Thus, in this work, the adsorption behavior of OH− on Fe2Mo(001), (010), (110) and (112) surfaces was simulated by ab initio calculations. And corresponding electronic effects were comparatively analyzed, the results of which show that the outmost surface of Fe2Mo changed significantly before and after adsorption, demonstrating that the Fe2Mo surface can be influenced by OH−. The results of adsorption energy, Mulliken population, density of states and electronic local function indicate that the Fe2Mo(001) surface has a greater adsorption trend, and the OH−/Fe2Mo(001)-b configuration has the largest adsorption energy. Electrons transfer from OH− to the Fe2Mo surface, and the adsorption type is chemisorption. The results provide a theoretical basis for studying the selective dissolution of Fe2Mo Laves phase in strong alkali solution.

酸処理によるケイ酸カルシウムからのナノコンポジット合成とCO<sub>2</sub>固定化特性の評価

Xonotlite, with a chemical formula of Ca6(Si6O17)(OH)2, has been widely used as a thermal insulation material due to its high porosity and chemical/physical stabilities. As a potential recycle use of Xonotlite, CO2 fixation is promising when considering its high alkali content and macroporous structure. In this study, Xonotlite was chemically activated to form nanocomposites of silica and calcium salt by optimizing an acid treatment. It was found that Xonotlite treated with acetic acid at 1.0 mol/L keeps the original macroporous structure of Xonotlite, and simultaneously segregates calcium salt on the surface of the residual silica. The nanocomposite of silica and calcium salt exhibits the capability of CO2 fixation and high cycle stability thanks to the unique structural feature of the composite.

Manufacture of alkali-activated cementitious materials using municipal solid waste incineration (MSWI) ash: Immobilization of heavy metals in MSWI fly ash by MSWI bottom ash

Based on the purpose of safe solid waste recycling, this work proposed a new method of co-treatment of municipal solid waste incineration fly ash (MSWIFA) and municipal solid waste incineration bottom ash (MSWIBA). The alkali-activated binder was synthesized from MSWIFA and MSIWBA by Ca/Si ratio design. The results showed that the maximum compressive strength of the samples at 56 d reached 8.8 MPa. A low concentration of alkali (6% Na2O dosage) favors the development of compressive strength when more MSWIFA is used in the binder system. The C-S-H gel is the main gel product in this case. In contrast, a high concentration of alkali (8% Na2O dosage) is required in the MSWIBA-based binder system. And C-(A)-S-H gels and N-A-S-H gels coexist under this condition. The results of leaching tests showed that after 56 d of curing, the reaction products limited the migration and leaching of potentially toxic elements from MSWIFA by physical encapsulation or chemical bonding. The immobilization efficiency of heavy metals such as Cd, Cr, Cu, Ni, Pb and Zn were above 98%, and their leaching concentrations were below the limits of the relevant Chinese standards.

Slagging-fouling evaluation of empty fruit bunch and palm oil frond mixture with bituminous ash coal as co-firing fuel

The empty fruit bunch (EFB) and palm oil frond mixture, called EFFR, can be utilized as co-firing fuel for coal-fired power plants to reduce carbon emissions. However, the addition of EFFR can influence the ash deposition characteristic of power plant fuel due to its high chlorine and alkali content. This study evaluates the slagging-fouling propensity of EFFR when blended with bituminous ash coal in several compositions. Theoretical methods using indices and the SCK ternary phase diagram, experimental procedure with drop tube furnace combustion, and ash observation methods utilizing visual and instrumental observations are carried out. The results show that co-firing EFFR can effectively reduce ash deposition. The slagging-fouling risk tendency slightly increases, adding up to 15 wt% EFFR has a higher slagging tendency, while the addition of 20 wt% EFFR has a higher fouling tendency. According to a thorough evaluation, co-firing 5–20 wt% EFFR with bituminous coal is still acceptable.

The Impact of Distinct Superplasticizers on the Degradation of Concrete Affected by Alkali-Silica Reaction (ASR).

The effect of two superplasticizers (SPs) with various equivalent (eq.) alkali contents (i.e., with 0.00009% and 4.1% of Na2Oeq, respectively) on the development of an alkali-silica reaction (ASR) was investigated through the use of multilevel assessment. This testing protocol showed promising results for evaluating concrete damage due to ASRs based on mechanical and microscopical testing protocols, specifically the stiffness damage test (SDT) and the damage rating index (DRI). Concrete specimens that incorporated the aforementioned SPs and distinct reactive aggregates (coarse and fine) were manufactured and then stored in conditions that enabled ASR development and were monitored over time. Upon reaching the desired expansion levels of this study, the concrete specimens were prepared for the multilevel assessment. The results show that the SP-incorporated concrete specimens with lower and higher alkali content yielded lower and higher deterioration results, respectively. This clearly confirms that while SP-incorporated concrete that contains SPs with a higher alkali content could increase the risk of ASR deterioration, those SPs with a very low amount of alkali content could act as a mitigation strategy against ASRs. Finally, an investigation into the influence of distinct SPs on the chemical composition of an ASR gel was conducted, which confirmed that the SP with a higher alkali content had the highest potential for further deterioration.

DFT insight of hydroxide degradation pathways for heterocyclic quaternary ammonium cations in anion exchange membranes

The alkaline stability of the heterocyclic quaternary ammoniums (QAs) is crucial for the long-term operation of anion exchange membrane fuel cells (AEMFCs). Here, we calculate the degradation barriers of 21 heterocyclic QAs and analyze the degradation mechanism systematically by density functional theory (DFT). We have found that the chair conformation and ring structure of heterocyclic QAs can inhibit Hoffman degradation of β-hydrogens and that methyl SN2 is the primary degradation pathway for most heterocyclic QAs. Higher ring strain and the introduction of electron-withdrawing groups are disadvantageous to the stability. The positions of substituted methyl affect the stability of the molecules significantly. Forming bicyclic structures is also an effective strategy to improve stability. Among tethering strategies of anion exchange membranes (AEMs), tethering at the 4-position is more stable than at the 1-position. The superacid-catalyzed condensation reaction is still the best AEM preparation strategy which balances the stability and synthetic difficulty. Compared with the experimental value, the average error of simulation is only 0.56 kcal mol−1. Our prediction method can also be extended to various alkali concentrations, and the results are consistent with the experiments. At low alkali concentrations, the heterocyclic QAs mainly degrade by SN2 reactions. At high alkali concentrations, the groups mainly degrade by Hofmann elimination reactions.

Pyrolysis and CO[formula omitted] gasification of barley straw: Effect of particle size distribution and chemical composition

We evaluate how the heterogeneity of the precursor may affect pyrolysis and CO2 gasification behavior aimed at activated carbon applications. Barley straw, ground and classified into five size ranges, is characterized by non-isothermal thermogravimetry tests at various heating rates. Fixed carbon and volatile matter contents decrease with particle size. Also, the finest fraction is enriched in minerals by exogenous contamination and accumulation of silicon-rich leaves. Faster pyrolysis kinetics are found for small sizes, caused by their higher alkali contents and heat-mass transfer rates. Char-CO2 gasification conversion rates show an unexpected behavior, not previously reported. Higher reactivity is found for the finest fraction, decreasing significantly at temperatures beyond 750 °C. The high alkali content of the finest fraction promotes the catalytic effect of minerals on gasification reactivity at lower temperatures, hindering the reaction at higher temperatures by forming low-melting-point potassium silicates. Results help improve pretreatment strategies to enhance activated carbon quality.

Constraining the deep dynamic process beneath the Bangong-Nujiang suture zone: A case study from the early cretaceous trachytic rocks

ABSTRACT The geodynamic processes that occurred beneath the Bangong – Nujiang suture zone during the evolution of the Indus – Yarlung Neo-Tethys and Bangong – Nujiang Meso-Tethys are unclear. We conducted a study of Early Cretaceous andesitic rocks from the Nyima area, north – central Tibet, to investigate these processes. The studied rocks have zircon U – Pb ages of 110–104 Ma and negative to positive εHf(t) values (−12.1 to+10.3). These rocks have affinities with trachytes, and have high total alkali contents and Na2O/K2O ratios (5–125). They also have high Sr (281–1409 ppm), Y (21.0–28.5 ppm), and Yb (2.00–2.65 ppm) contents, and exhibit depletions in Nb, Ta, and Ti. Such features indicate these rocks are not adakites, but are similar to typical arc rocks. The geochemical and isotopic data suggest the studied rocks were formed by partial melting of amphibolite-facies oceanic lithosphere, with the addition of enriched sedimentary materials. Based on the regional crustal evolution, we suggest that the Nyima andesitic rocks formed by melting of Bangong – Nujiang oceanic lithosphere. As such, the Early Cretaceous igneous rocks along the central Bangong – Nujiang suture zone were not associated with northward subduction in the Indus – Yarlung Neo-Tethys.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Study of the interaction between a Mn ore and alkali chlorides in chemical looping combustion

Chemical looping combustion (CLC) is a novel technology for heat and power generation with inherent CO2 capture. Using biomass in CLC (bio-CLC), negative CO2 emissions can be attained. Biomass usually contains high content of alkalis (mainly K and Na) which can be problematic in the process, such as potential alkali-bed interaction, and this is the focus of current work. This work uses charcoal with and without the impregnation with alkali chlorides, KCl and NaCl. The results are compared to previous data from samples impregnated with K2CO3 and Na2CO3. A low-alkali braunite manganese ore is used as bed material to study the oxygen carrier interaction with the alkalis in cyclic experiments at 950 °C in a quartz batch fluidized-bed reactor. As compared to charcoal without alkali impregnation, the impregnation with KCl, NaCl, K2CO3, and Na2CO3 can improve the rate of gasification by a factor of 4, 3, 10, 8, respectively. Partial-defluidization of the braunite particles was found with all the alkali-fuels, although the extent differed, e.g., K2CO3 and KCl resulted in earlier onset of defluidization than Na2CO3 and NaCl. Further, indications of partial defluidization were earlier and more permanent with the carbonates than the chlorides. Partial agglomeration with soft agglomerates of the bed was observed, while hard agglomerations were never seen. Accumulation of K, Na, Si, and Ca was found in the agglomerates after cycles with K2CO3-charcoal and Na2CO3-charcoal, while little K and Na was detected in the bridges between particles after the KCl and NaCl cycles. A significant fraction of the alkali added was found in the oxygen carrier, with 80% or more being retained for the Na salts, and around 40% for the K salts. There was no clear difference between chlorides and carbonates with respect to retention. The fresh and used braunite have very similar reactivity with CH4 and H2, whereas some decrease in reactivity is noticed with CO.

Molecular level insight of thiocyanate degradation by Pseudomonas putida TDB-1 under a high arsenic and alkaline condition

It is a big challenge to bioremediate thiocyanate pollution in the gold extraction heap leaching tailings and surrounding soils with high contents of arsenic and alkali. Here, a novel thiocyanate-degrading bacterium Pseudomonas putida TDB-1 was successfully applied to completely degrade 1000 mg/L thiocyanate under a high arsenic (400 mg/L) and alkaline condition (pH = 10). It also leached the contents of thiocyanate from 1302.16 to 269.72 mg/kg in the gold extraction heap leaching tailings after 50 h. The maximum transformation rates of S and N in thiocyanate to the two finial products of SO42− and NO3− were 88.98 % and 92.71 %, respectively. Moreover, the genome sequencing confirmed that the biomarker gene of thiocyanate-degrading bacterium, CynS was identified in the strain TDB-1. The bacterial transcriptome revealed that critical genes, such as CynS, CcoNOQP, SoxY, tst, gltBD, arsRBCH and NhaC, etc. in the thiocyanate degradation, S and N metabolisms, and As and alkali resistance were significantly up-regulated in the groups with 300 mg/L SCN− (T300) and with 300 mg/L SCN− and 200 mg/L As (TA300). In addition, the protein-protein interaction network showed that the glutamate synthase encoding by gltB and gltD served as central node to integrate the S and N metabolism pathways with thiocyanate as substrate. The results of our study provide a novel molecular level insight for the dynamic gene expression regulation of thiocyanate degradation by the strain TDB-1 with a severe arsenic and alkaline stress.