Precipitation Of Cr Research Articles

Mechanism investigation on high-performance Cu-Cr-Ti alloy via integrated computational materials engineering

In this work, the influence of different Ti additions on microstructure and property in Cu-Cr alloys has been studied and the primary relationship of processing-microstructure-property in Cu-Cr-Ti alloy has been constructed via the CALPHAD-based Integrated Computational Materials Engineering (ICME) approach and experimental validation. The peak-aged Cu-0.5Cr-0.2Ti alloy offers an excellent combination of hardness 192.6 HV, tensile strength 629.3 MPa, yield strength 603.0 MPa, electrical conductivity 51.3 %IACS and elongation 10.9 %. The calculated results suggest that the addition of Ti could promote the nucleation and hinder the growth of Cr precipitate in Cu-Cr-Ti alloys during aging treatment, which may promote the homogeneous formation of small-size precipitate Cr and improve the strength of the Cu-Cr alloy. Microstructural characterization has validated the calculation results and revealed that the exceptional properties of this alloy are mainly attributed to nano-scale Cr precipitates achieved through the optimal thermomechanical processing from present ICME. Thus, the present ICME flowchart is applicable to design alloy composition and optimize the processing for the desired microstructure and property in engineering industries.

Nanoscale phase separations in as-fabricated thick super duplex stainless steels

Nanoscale phase separations, and effects of these, were studied for thick super duplex stainless steel products by atom probe tomography and mechanical testing. Although nanoscale phase separations typically occur during long-time service at intermediate temperatures (300–500° C, our results show that slowly cooled products start to develop Fe and Cr separation and/or precipitation of Cu-rich particles already during fabrication. Copper significantly slowed down the kinetics at the expense of Cu-rich particle precipitation, where the high-copper material subjected to hot isostatic pressing (HIP), with Δt500–400 of 160 s and the low-copper hot-rolled plate with Δt500–400 of 2 s had the same level of Fe and Cr separation. The phase separations resulted in lower toughness and higher hardness of the HIP material than for hot-rolled plate. Therefore, both local cooling rate dependent and alloy composition governed variations of phase separations can be expected in as-fabricated condition.

A study into the behaviour of nickel, cobalt and metal impurities during partial neutralisation of synthetic nickel laterite pressure leach solutions and pulps

The behaviour of nickel (Ni), cobalt (Co) and major impurities such as aluminium (Al), trivalent chromium [Cr(III)] and ferric iron [Fe(III)] during the partial neutralisation of synthetic pressure acid leach (PAL) liquors and pulps was investigated. Ferric iron precipitation took place between pH85°C 2 to 3, and up to 54% of Cr(III) and 42% of Al were co-precipitated with Fe(III). Haematite appeared to act as a seed and promote the removal of Fe(III) from solution at a pH85°C as low as 2. Precipitation of the remaining Al and Cr(III) from solution did not commence until at or above pH85°C 3.5, and virtually went to completion at pH85°C 4 (96% precipitation extent). There was a linear correlation between the %Cr(III) precipitation and %Al precipitation from solution, which suggests that the behaviour of the two species is related and that Cr(III) is unlikely to behave independently in solution. Nickel and cobalt losses were strongly dependent on pulp pH, and valuable metal losses rapidly climbed above pH85°C 3 and further increased after 1 h of ageing; this behaviour appears to be consistent with adsorption processes. Cobalt losses were found to increase significantly in the presence of haematite whilst Ni losses were unchanged, suggesting that there is partitioning of Ni and Co during partial neutralisation of PAL pulps with Co preferentially adsorbing onto haematite. Final Ni losses were on average 1.95% and were unaffected by the presence of haematite; final Co losses were 0.38% in the absence of haematite and increased to 3.30% in the presence of haematite.

Simulating the migration and species distribution of Cr and inorganic ions from tanneries in the vadose zone

The pollution in soils and groundwater caused by the tannery have attracted public attention. However, few studies have been done on the migration and species distribution of Cr and coexisting ions produced by tanning in the vadose zone. In this paper, an in-production tannery and a suspended tannery were selected to compare the migration of Cr and other inorganic ions from tanneries in the vadose zone. Results showed that the sewage treatment station and the temporary waste storage site had the highest concentration of pollutants. Cr exhibited a cumulative effect in the middle soil layer (100–300 cm) in the suspended tannery. However, in the in-production tannery, the cumulative effect occurred only at the temporary waste storage site. The distribution of pollutants in the soils at different depths was fixed in the suspended tannery field. But in the in-production tannery field, it was closely related to daily production. Visual MINTEQ showed that the saturation index of a species of Cr was positive or negative simultaneously in the two sites, indicating that (1) the change of saturation index of Cr had no relationship with operation of tannery. (2) the influence of Cr precipitation or dissolution was related to the source strength, the coexisting ions, and pH. This study contributed to understanding the migration of characteristic pollutants caused by tanneries in the vadose zone under different external environments, and provided a reference for the quantification calculation of the source load of pollutants caused by industrial infiltration into the groundwater.

Mechanism and enhancement of Cr(VI) contaminated groundwater remediation by molasses.

The remediation of Cr(VI)-contaminated groundwater with molasses has many advantages compared with traditional in-situ chemical methods, including high cost-effectiveness and negligible secondary contamination. Hence, the reaction conditions and mechanisms of molasses were investigated in this study. The results showed that Cr(VI) was chemically reduced by molasses at acidic pH (3.0), wherein the dominant active components were the hydroxyl and carbonyl groups of molasses. At neutral pH (7.0), molasses mainly acted as an electron donor for direct or indirect reduction of Cr(VI) by microorganisms. The main functional microorganisms were Bacillus and Clostridium Sensu Stricto. Compared with chemical reduction, bio-reduction could completely reduce higher concentrations of Cr(VI) when molasses was added at a concentration of 3g/L. Ascorbic acid was added to promote the removal rate of bioremediation. Owing to the antioxidant properties of ascorbic acid, the reaction rate increased by 9.3% and 37.5% when 0.05g/L of ascorbic acid was added to the 50 and 100mg/L Cr(VI) bioremediation systems, respectively. Due to the decrease in pH during bioremediation, NaHCO3 was added to buffer the pH changes and promote Cr(III) precipitation. Compared with the addition of NaHCO3 and molasses simultaneously, separate additions were more effective for precipitation. Furthermore, X-ray absorption near-edge structure analysis revealed that after chemical reduction and biological reduction, Cr was attached to the solid medium in the form of Cr(III).

Influence of the applied pressure on the microstructure evolution of W-Cr-Y-Zr alloys during the FAST process

Field assisted sintering technology (FAST) has been widely employed for powder materials consolidation. The assisted-current and applied pressure in FAST facility strongly affect the microstructures of the consolidated powder materials. In this work, the influence of the applied pressure on the W-11.4Cr-0.6Y-0.4Zr alloy during FAST consolidation at 1400 °C by varying the applied pressures (10 MPa-60 MPa) is investigated. The amounts of Cr-rich phase in W-Cr-Y-Zr sintered samples decreases with an increase of the applied pressure. This is owing to the local overheating, which enhances the Cr precipitation during the FAST process. In addition, the average grain size increases as the applied pressure rises from 10 MPa to 40 MPa. With the further increase of applied pressure to 60 MPa, the average grain size decreases. High applied pressure induces the deformation of the graphite punch, which results in a low thermal resistance. Therefore, the reduction of the grain size is mainly related to the low actual temperature of the sample. Under an applied pressure of 60 MPa, the high density (∼99.5 %), fine grain and homogeneous microstructure of W-11.4Cr-0.6Y-0.4Zr alloy can be obtained.

Detecting Intergranular Phases in UNS N07725: Part I. Adapting the Double-Loop Electrochemical Potentiokinetic Reactivation Test

Precipitation hardened nickel-based Alloy 725 (UNS N07725) has been proven susceptible to hydrogen embrittlement in oil and gas production. Moreover, current standards cannot differentiate unequivocally between acceptable and affected microstructures, making the development of an appropriate quality control test a priority for the oil and gas industry. Recently, Alloy 725 failures were associated with the precipitation of nanoscale Cr- and Mo-rich phases at grain boundaries (GBs). Since these intergranular precipitates could lead to Cr- and Mo-depletion along the decorated GBs (i.e., sensitization), the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test was explored as an alternative approach to detect affected microstructures. Herein, the DL-EPR technique was optimized for Alloy 725 by testing three types of samples with different degrees of sensitization, including a full GB-decorated microstructure that was shown prone to hydrogen embrittlement in oil and gas service. The optimized DL-EPR test conditions were 2 M HCl + 1 M H2SO4 + 10−4 M KSCN aqueous solution at 30 °C with a 1.667 mV s−1 scan rate and a vertex potential of Ecorr + 700 mV. Results were reproducible and consistent with the degree of GB decoration determined using metallographic methods. The test procedure developed herein could lead to the standardization of the DL-EPR method for Alloy 725.

Effect of cobalt on precipitation in Fe-Cr-Co-Mo-Ni-C stainless steels

Nano-scale precipitation is critical for martensitic steels to achieve ultra-high strengths. To date, there is a lack of in-depth understanding about tailoring Co addition to optimize strengthening precipitations in Fe-Cr-Co-Mo-Ni-C steels. This research reveals that a high addition of Co in a Fe-Cr-Co-Mo-Ni-C steel significantly promotes multiple precipitation of Mo-rich intermetallic compounds (IMCs), carbides and α’-Cr, and achieve an exceptional hardening effect during aging at 540 °C. In particular, a variation of Co content from 5.1 to 12.8 wt% enhances α’-Cr precipitation, and accelerates precipitation kinetics of Mo-rich phase during early-stage aging. However, few influences were observed on the solubility of Mo and equilibrium fraction of Mo-rich phases, according to both long-term aged microstructures and thermodynamic equilibrium calculation.

Effect of CaO and Ca(OH)2 doses in the precipitation of Cr (III) and sludge formed from characteristic solution used in Mexican tanneries

We conducted a series of experiments to determine the effect of doses of CaO and Ca(OH)2 added to a synthetic solution, prepared with the same salt of Cr as that found in Mexican tanneries, to precipitate the chromium and determine the amount of sludge. The stirring was kept at 150 rpm during 10 min of time of contact between reagents, followed by measurements of Cr in the supernatant and determination of the amount of sludge. The study was carried out in a wide range of dose of alkalis, including the stoichiometric value, and also we vary the initial concentration of Cr at fixed alkali doses, and duplicate both the concentration and alkali dose maintaining the stoichiometric ratio. To remove almost 100% of Cr3+, a stoichiometric or higher dose of alkali was necessary; nonlinear behavior was found between the excess of alkali and pH. Also, the addition of an excess of Cr in the initial solution was not reflected directly in remaining chromium in the supernatant. Finally, it was found that some excess of alkali contribute to increase the sludge because the impossibility to be dissolved at operation conditions.

Paper waste sludge derived-hydrochar modified by iron (III) chloride for effective removal of Cr(VI) from aqueous solution: Kinetic and isotherm studies

This work investigated Cr(VI) adsorption onto pristine and iron modified hydrochar (PSH and PSH-Fe15, respectively) which were generated from paper waste sludge. The results indicate that the hydrothermal carbonization temperature of 200 °C was the most suitable for hydrochar production. The batch experiments and the adsorption isotherm and kinetic of Cr(VI) onto PSH and PSH-Fe15 were conducted and used to elucidate the adsorption mechanisms. The results demonstrate that the Cr(VI) adsorption capacity and efficiency onto both PSH and PSH-Fe15 reached equilibrium after 120 min at pH 3 and an initial Cr(VI) concentration of 60 mg/L. In this condition, the adsorption capacities were 5.94 mg/g and 8.67 mg/g and the removal efficiencies were 39.62 % and 57.80 % for PSH and PSH-Fe15, respectively. The adsorption processes were well described by the Sips and Redlich–Peterson isotherm models (with R2 of 0.9895, 0.9987 and 0.9947 and 0.9981 for PSH and PSH-Fe15, respectively) and pseudo-second-order kinetic model (with R2 of 0.98412 and 0.99681, respectively, for PSH and PSH-Fe15). The analysis of characteristics of PSH and PSH-Fe15 indicates the rough and heterogamous surface structures. Moreover, there was presence of iron ions on PSH-Fe15 based on EDS analysis and appearance of oxygen-containing surface functional groups recorded through FTIR results. Finally, it was observed that the reduction of Cr(VI) to Cr(III) caused by iron ions on PSM-Fe15’s surface and the presence of OH groups resulting in the precipitation of Cr(OH)3 on the hydrochar’s surface was the main mechanism of Cr(VI) adsorption onto PSH-Fe15.

Experiments to determine the suitability of sodium dithionite treatment for a Cr(VI) groundwater plume in a deep aquifer of the United States Southwest

Legacy industrial waste has left groundwater plumes of hexavalent Cr (Cr(VI)) that requires treatment, predominantly by reduction to Cr(III) and subsequent precipitation. One promising technology is the injection of a strong reducing agent, sodium dithionite, to create an in-situ redox barrier, but implementation requires a comprehensive understanding of the reactions occurring with dithionite injection. Batch and column experiments were conducted with aquifer sediments to determine both the significant reactions and efficacy of sodium dithionite treatment for a groundwater plume of hexavalent chromium. The batch experiments demonstrate consumption of dithionite over the experiment (disappearance by 43 d) concurrent with leaching of about 1 mM Fe from the sediments. Reactions deduced from batch experiments were incorporated into a 1-D numerical model to simulate reactions occurring during the column injection. The treatment was able to successfully reduce approximately 30 pore volumes of groundwater containing 800 µg kg−1 Cr(VI). The experiments also demonstrate that although mineral forms of Fe are important phases in the reduction of Cr(VI), Fe alone cannot account for the entire reduction capacity imparted to the sediments. Rather, the correlation between Cr and reduced S retained in the columns, combined with Scanning Electron Microscopy (SEM) of treated sediments, suggest that formation of reduced S phases contributes to the prolonged reduction capacity.

Carbon fiber-based flow-through electrode system (FES) for Cr(VI) removal at near neutral pHs via Cr(VI) reduction and in-situ adsorption of Cr(III) precipitates

Cr(VI) reduction to Cr(III) and subsequent Cr(III) precipitation is an extensively employed strategy to treat Cr(VI)-contaminated wastewater, which generally generates large volumes of sludge that need expensive disposal, and requires high chemical cost for pH adjustment. Herein, flow-through electrode system (FES) with a sequential oxidation-reduction process was employed to simultaneously reduce Cr(VI) and in-situ precipitate Cr(III), thereby simplifying the treatment processes and providing potentials to recollect Cr resource. The influent (10 mg/L Cr(VI)) with near neutral pHs (6–8) was first oxidized by the anode with H+ ions generation via H2O oxidation, leading to the anode-treated effluent turned into strong acidic with pH below 3.5. Subsequently, under acidic condition, the Cr(VI) species were prone to reduce to Cr(III) on the cathode. The multi-cathode FESs (1A + nC) equipped with one counter anode (1A) and multiple cathodes (nC) were constructed to enhance the Cr(VI) reduction by providing more cathode reactive sites and in-situ Cr(III) precipitation by maintaining near neutral effluent pHs. The flow-through flux and applied voltage were optimized to be 500 L/h/m2 and 2.6 V, under which Cr species were undetectable in effluent of 1A + 4C FES within continuous operation time of 30 min. Regenerating the Cr(OH)3-passivated CFF electrodes and recollecting the Cr waste resource were easily accomplished by using a small volume of acidic solution with reversed applied voltage. This study suggested that carbon fiber-based FES with a sequential oxidation-reduction process can be a feasible approach for remediation and recovery of Cr(VI) contamination.

Diffusion dialysis and extraction integrated system for recovery of cobalt(II) from industrial effluent

This paper presents multistage hydrometallurgical separation of Co(II) from wastewater, achieved in an integrated system containing diffusion dialysis (DD) to decrease the acidity of the industrial effluent – pregnant leach solution (PLS), followed by precipitation of Al(III), Fe(III) and Cr(III) hydroxides, selective extraction of Co(II) with bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), stripping of Co(II) from the loaded organic phase to form an electrolyte. DD results indicate that minimum metal ion content in the dialysate and high concentration of H+ (1.5−3 M) can be achieved by conducting the process at a low flow rate, but for a longer time. The feed after DD was effectively purified by precipitation of Cr(III), Al(III) hydroxides, and some admixtures of Cu(II) and Fe(III) to ensure that those metals will not disturb the liquid-liquid extraction of Co(II) at pH 5.2. High distribution ratio values for Co(II) extraction mean that ions of this metal can be selectively separated from the remaining ions present in the feed, especially Ni(II), and transported to the organic phase. The application of H2SO4 solution and the dialysate as stripping phases indicates that the dialysate more efficiently stripped most of the metal ions from the extract, thus forming Co(II) rich electrolyte for further electrodeposition of the metal. Finally, Co(II) electrowinning from a model stripping solution was investigated and the preliminary results showed that good quality metallic cobalt can be deposited.

Investigating defect evolution during thermal treatment in Ni–Cr alloy using positron annihilation spectroscopy

Defects evolved during thermal treatment in high Cr content Ni–Cr alloy have been studied using Positron lifetime and coincidence Doppler broadening spectroscopy complemented with microscopic technique. The single-phase gamma-quenched specimen obtained by solutionization at 1200 °C has been thermally aged at 650 °C and 800 °C. Thermal treatment resulted in the phase transformation of the matrix through precipitation of Cr. It is seen that solutionization treatment followed by quenching resulted in the stabilization of thermal vacancies generated at 1200 °C which effectively trap the positrons. The results infer that these vacancies may form vacancy-Cr complexes which act as nucleation site for Cr aggregation. Positron lifetime and momentum distribution of annihilation electrons indicated that in the aged alloys, positrons are trapped in vacancy-like defects (vacancy clusters/vacancy-solute complex) and the interface between Cr precipitate and matrix, the latter becoming more predominant with subsequent ageing. At the highest ageing studied, vacancy-like defects are evolved within the Cr precipitates. The results indicated that positron trapping sites (vacancies and precipitate interface) are not specific to either Ni or Cr atoms which surround the trapping site in nearly equal proportion. Therefore, unambiguous identification of the defect type at each stage of thermal treatment becomes difficult. Considering positron trapping at the surface of precipitates, we have calculated positron specific trapping coefficient to be ~ 1.33 × 10−6 cm3 s−1, which is of the order estimated for large voids and estimated the number density of precipitates.

Recovery of chromium from vanadium precipitated solution by precipitation with lead salt and leaching with sodium carbonate

The recovery of chromium from vanadium precipitated solution obtained by adding Ca(OH)2 into the chromium-containing vanadate solution and ball milling was investigated by precipitation with lead salt and leaching with sodium carbonate. It has been found that chromium can be effectively enriched by adding PbCO3. The precipitate is the mixture of PbCO3 and PbCrO4∙PbO. The concentration of Cr residue in the solution can be decreased to 16.0 mg/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio 4.0 and adjusting the pH to 12.5 with NaOH stirring for 180 min at 20 °C. Then the precipitates were leached with hot Na2CO3 solution under pH 10.0 at 50 °C to obtain the leach solution containing Na2CrO4 and the leach residue containing PbCO3. After filtration, the leach residue was reused in Cr precipitation and the leach solution was used to circularly leach the Cr precipitate until Na2CrO4 near saturation. Finally, the product of Na2CrO4∙4H2O with purity 99.3% was obtained by evaporation and crystallization of the leach solution.

Mechanisms of enhanced hexavalent chromium removal from groundwater by sodium carboxymethyl cellulose stabilized zerovalent iron nanoparticles

Chromium (Cr) contamination poses serious threats to the environment and human health. Thus, batch and column experiments were performed to investigate hexavalent chromium [Cr (VI)] removal from solution and porous media using nanoscale zerovalent iron nanoparticles (NZVI) stabilized by sodium carboxymethyl cellulose (CMC). Batch experiments indicated that the mass ratio of Fe/CMC = 1, the presence of 150–200 mg L−1 CMC and lower ionic strength led to optimum Cr (VI) removal in aqueous solution. Column experiments demonstrated that Cr (VI) removal was enhanced with decreasing solution pH and increasing CMC-NZVI concentration. The presence of CMC can increase Cr (VI) removal by NZVI in both aqueous solution and porous media by complexation precipitation of Cr (VI) compounds and better dispersion of NZVI. X-ray photoelectron spectroscopy (XPS) analysis revealed that an appropriate amount of CMC supported the redox reaction of Cr (VI) and NZVI. The removal of Cr (VI) through columns was 20.8% and 88.5% under no additional CMC and optimized CMC content, respectively. However, Cr (VI) removal decreased to 64.6% under excessive CMC content. The CMC modified NZVI nanoparticles were characterized by XRD, XPS and TEM techniques. These findings imply that CMC can be used as an effective stabilizer on NZVI which can in turn be applied for the efficient removal of Cr (VI) from industrial wastewater and groundwater.

Performance and potential mechanism of Cr(VI) reduction and subsequent Cr(III) precipitation using sodium borohydride driven by oxalate

The method of treating high concentrations of Cr(VI) alone by NaBH4 has proved feasible, but the effects of the coexistence of Cr(VI) and organic compounds have not been evaluated. The objective of this study was to explore the potential mechanism by which oxalate affects the reduction of high concentrations of Cr(VI) treated by sodium borohydride (NaBH4) and the subsequent precipitation of Cr(III). The results show that Cr(VI) reduction could be gradually promoted by oxalate (1.0–10 mM). Compared with the control solution, the reduction of Cr(VI) in a 10 mM oxalate solution could be increased from 56.6% to 99.1%. Particularly, the promotion of Cr(VI) reduction attributed to the enhancement of OH- production from NaBH4 hydrolysis due to the increasing concentration of C2O42- species, forming conjugated acid–base pairs in the form HC2O4-–C2O42-, which provided an effective buffer. In 0.10–0.40 mM oxalate–Cr(VI)–NaBH4 systems, the resulting Cr(III) could precipitate at different levels within 20 h, and showed settlement rates in the range of 8.8% and 95.8%, but no precipitate was found in 1.0–10 mM oxalate–Cr–NaBH4 systems. This is related to whether there was a sufficient oxalate dosage, which could be complexed with Cr (III) at a molar ratio of 1:1. The precipitates were analysed by means of electron spin resonance (ESR), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), indicating that Cr (III) could support oxalate coprecipitation. The results of the present study reveal the influence of oxalate on Cr(VI) reduction and subsequent Cr (III) precipitation, which are of great significance to the application of NaBH4 in the treatment of industrial wastewater containing Cr(VI)–oxalate.

Effect of deformation and aging treatment on the microstructure and properties of Cu-0.45Cr-0.14Ti (wt.%) alloy

The microstructure and properties of Cu-0.42Cr (wt.%) and Cu-0.45Cr-0.14Ti (wt.%) alloy subjected to cold rolling and aging treatment are investigated through tensile testing, electrical conductivity measurement, scanning electron microscopy, and transmission electron microscopy. Results show that the tensile strength of Cu-0.45Cr-0.14Ti (wt.%) alloy enhances as the degree of deformation increases, but the degree of deformation slightly influences electrical conductivity. When deformation is changed, electrical conductivity is basically unchanged. The good combination of strength and electrical conductivity, which reach 610 MPa and 55.4% IACS, respectively, can be obtained in the Cu-0.45Cr-0.14Ti (wt.%) alloy after 80% cold rolling and aging at 450 °C for 15 min. Ti inhibits the growth of the Cr precipitation phase and enhances the precipitation strengthening effect. Ti mainly exists in the matrix in the form of solute atoms, which do not form a separate lattice structure after aging treatment.

Creep induced precipitation of the (Cr,Mo)5B3-type boride in γ/γ′ eutectic of a Ni-based superalloy

Boron segregation and boride formation at grain boundaries are generally accepted in Ni-based superalloys. However, the addition of boron was found to result in the formation of a high density of nanosized M5B3 (where M is a mixture of Cr, Mo) particles in γ/γ′ eutectics of a Ni-based superalloy during high-temperature creep in this work. M5B3 phase precipitated at γ/γ′ eutectics keeps a well-defined orientation relationship with the eutectics, which is [001]γ/γ′//[001]M5B3, (020)γ/γ′//(130)M5B3. And these nanosized borides could block dislocation slip, result in stress concentration surrounding γ/γ′ eutectics and facilitate crack initiation at γ/γ′ eutectic/matrix interface during the creep at high temperatures.

Electrochemical Cr(VI) removal from aqueous media using titanium as anode: Simultaneous indirect electrochemical reduction of Cr(VI) and in-situ precipitation of Cr(III)

In this work, a novel method for complete Cr(Ⅵ) removal was achieved in a single-chamber cell with titanium (Ti) as anode via simultaneous indirect electro-reduction of Cr(Ⅵ) and in-situ precipitation of Cr(Ⅲ). The Cr(Ⅵ) and total Cr removal, and electric energy consumption were optimized as a function of electrochemical reactor, current density, initial Cr(Ⅵ) and chloride (Cl−) concentration, and initial solution pH. The maximum Cr(Ⅵ) and total Cr removal efficiency reached 80.5 and 79.4% respectively within 12 h at current density of 10 mA cm−2 as initial Cr(Ⅵ) concentration was 0.078 mM. Decreasing the initial solution pH was beneficial to Cr(Ⅵ) reduction, but Cr(Ⅲ) precipitation was inhibited, resulting in the poor total Cr removal. The suitable Cl− concentration guaranteed sufficient reducing agents (Ti3+ and Ti2+) for Cr(Ⅵ) removal. The reaction mechanism demonstrated that Ti anode could be corroded to produce Ti3+ and Ti2+, which provided the electrons for reduction of Cr(Ⅵ) to Cr(Ⅲ). Simultaneously, the solid products (Ti2O(6x−y−z+52)Cl2yCr2x(OH)2z(s)) were in-situ formed and precipitated from the solution due to the continuous generation of hydroxyl ion (OH−) from cathode. This study might provide a new electrochemical method with non-precious metal as the electrode for complete Cr(Ⅵ) removal from aqueous media.