Impact Of Sulfate Research Articles

Removal of selenate from wastewater using a bioelectrochemical reactor: The importance of measuring selenide and the role of competing anions

Removal of selenate (SeO42-) from selenate-contaminated wastewater is challenging due to the commonly co-existing and competing anions of sulfate (SO42-) and nitrate (NO3-). This study investigates SeO42− reduction to elemental selenium (Se0) in a cathode-based bioelectrochemical (BEC) reactor and a conventional biofilm reactor (i.e., an upflow anaerobic reactor). The simulated wastewater contained SeO42− at a typical concentration of 5 mg Se/L, SO42− at a typical concentration of 1000 mg S/L, and NO3− at concentrations that varied from 0 to 10 mg N/L. The impact of sulfate on the BEC reactor was much lower than that on the conventional reactor: The selenium removal, defined as (selenate in influent – dissolved selenium in effluent)/selenate in influent, was 99 % in the BEC reactor versus 69 % in the conventional biofilm reactor. The lower selenium removal in the conventional reactor was mainly due to the >10 times higher reduction of sulfate, which directly caused competition between sulfate and selenate for the common resources such as electrons. The more reduction of sulfate in the conventional reactor further led to 45 times higher production of selenide. Selenide is usually assumed to be minimal and therefore not measured in the literature. This simplification may significantly overestimate selenium removal when the influent sulfate concentration is very high. NO3- in the influent of the BEC reactor promoted selenium removal when it was less than 5.0 mg N/L but inhibited selenate removal when it was more than 7.5 mg N/L. This was supported by the microbial community analysis and intermediate (nitrite) analysis.

Enhancement of medium-chain fatty acids production from sludge anaerobic fermentation liquid under moderate sulfate reduction

In recent years, there has been a marked increase in the production of excess sludge. Chain-elongation (CE) fermentation presents a promising approach for carbon resource recovery from sludge, enabling the transformation of carbon into medium-chain fatty acids (MCFAs). However, the impact of sulfate, commonly presents in sludge, on the CE process remains largely unexplored. In this study, batch tests for CE process of sludge anaerobic fermentation liquid (SAFL) under different SCOD/SO42− ratios were performed. The moderate sulfate reduction under the optimum SCOD/SO42− of 20:1 enhanced the n-caproate production, giving the maximum n-caproate concentration, selectivity and production rate of 5.49 g COD/L, 21.4% and 4.87 g COD/L/d, respectively. The excessive sulfate reduction under SCOD/SO42− ≤ 5 completely inhibited the CE process, resulting in almost no n-caproate generation. The variations in n-caproate production under different conditions of SCOD/SO42− were all well fitted with the modified Gompertz kinetic model. Alcaligenes and Ruminococcaceae_UCG-014 were the dominant genus-level biomarkers under moderate sulfate reduction (SCOD/SO42− = 20), which enhanced the n-caproate production by increasing the generation of acetyl-CoA and the hydrolysis of difficult biodegradable substances in SAFL. The findings presented in this work elucidate a strategy and provide a theoretical framework for the further enhancement of MCFAs production from excess sludge.

Substrate-dependent strategies to mitigate sulfate inhibition on microbial reductive dechlorination of polychlorinated biphenyls

Sulfate widely co-exists with polychlorinated biphenyls (PCBs) at various concentrations in the subsurface environment. Previous studies have suggested that sulfate often hampers microbial degradation of aliphatic chlorinated solvents such as chloroethenes. However, the impact of sulfate on microbial reductive dechlorination of aromatic PCBs and the underlying mechanisms have received limited attention. Likewise, strategies to mitigate such inhibition remain scarce. Here we found that the mechanisms and mitigation strategies of sulfate inhibition on PCB dechlorination were substrate-dependent. Under electron donor-limiting conditions, even a low concentration of sulfate (2 mM) resulted in a decreased PCB dechlorination rate by 88.7% in a co-culture comprising Dehalococcoides mccartyi CG1 and the sulfate-reducing bacterium Desulfovibrio desulfuricans F1, an inhibition which was attributed to the competition for electron donor between sulfate reduction and PCB dechlorination. As expected, re-amendment of 5 mM lactate effectively re-initiated PCB dechlorination. However, in the presence of a higher concentration of sulfate (5 mM), the PCB dechlorination rate in the co-culture was 77.7% lower than in the control, even with excessive electron donor supply. This inhibition was linked to high concentration of sulfide (∼5 mM) produced from sulfate reduction, as suggested by high availability of electron donor, recovery of dechlorination activity after removal of sulfide, and negligible influence of sulfate on PCB dechlorination in the axenic culture of D. mccartyi CG1. Indeed, sulfide (>5 mM) was found to directly suppress expression of PCB-dechlorinating reductive dehalogenase gene. The highest transcriptional level of pcbA1 was 2.9 ± 0.3 transcripts·cell−1 in the presence of ∼5 mM sulfide, which was increased to 37.4 ± 5.0 transcripts·cell−1 when sulfide was removed. Under this scenario, introduction of ferrous salts (5 mM) efficiently alleviated sulfide inhibition on PCB dechlorination. Interestingly, the augmentation of methanogens in the co-culture was also effective in mitigating sulfide inhibition on PCB dechlorination, offering a new approach to protect Dehalococcoides under sulfide stress. Collectively, these findings deepen our understanding of the influence of sulfate on microbial reductive dechlorination of PCBs and contribute to developing appropriate strategies based on geochemical conditions to alleviate sulfate inhibition during bioremediation of PCB-contaminated sites.

Impact of Sulfate in the Sand on the Compressive Strength of Metakaolin-Based Geopolymer Mortar

The advancement of cement alternatives in the construction materials industry is fundamental to sustainable development. Geopolymer is the optimal substitute for ordinary Portland cement, which produces 80% less CO2 emissions than ordinary Portland cement. Metakaolin was used as one of the raw materials in the geopolymerization process. This research examines the influence of three different percentages of sulfate (0.00038, 1.532, and 16.24) % in sand per molarity of NaOH on the compressive strength of metakaolin-based geopolymer mortar (MK-GPM). Samples were prepared with two different molarities (8M and 12M) and cured at room temperature. The best compressive strength value (56.98MPa) was recorded with 12M with lower sulfate content (0.00038%) at 28 days. Also, an inverse relationship is recorded between the increasing sulfate percentages in the sand and the compressive strength values of (MK-GPM). A higher reduction in the compressive strength results at 28 days (60.88% per 8M/NaOH) and (62.23% per 12M/NaOH) was associated with a higher percentage of SO3 in the sand (16.24%).

Impact of Sulfate in the Sand on the Absorption and Density of Metakaolin-Based Geopolymer Mortar

Impact of Sulfate in the Sand on the Absorption and Density of Metakaolin-Based Geopolymer Mortar

Ion-Exchange Treatment of Perfluorinated Carboxylic Acids in Water: Comparison of Polystyrenic and Polyacrylic Resin Structures and Impact of Sulfate on Their Performance.

The removal of three perfluorinated carboxylic acids (PFCAs)—PFHpA, PFOA, and PFNA—in ultrapure and river water was evaluated using two anion-exchange resins—previously unreported macroporous polystyrenic A-500P and a more widely studied macroporous polyacrylic A-860. Both resins had similar properties, allowing direct comparison of PFCA removal performance between the two resin structures/matrices. This study also presents a new gas chromatography–mass spectrometry (GC/MS) method developed for PFCA analysis in water. In ultrapure water, A-500P exhibited higher removal capacity and faster removal compared to A-860, suggesting greater effectiveness of the polystyrenic structure compared to the polyacrylic structure. In the Grand River water, the target PFCAs were well removed by A-500P but not A-860. However, both resins achieved similarly high overall reductions of dissolved organic carbon (∼75%), suggesting, later confirmed in ultrapure water experiments, that inorganic anions (sulfate particularly) were the dominant competitors for the A-860 resin. The uncharged styrenic and acrylic beads (base materials) of the two tested resins were unable to remove PFOA, implying that the dominant removal mechanism involves charge interactions between the negatively charged PFCA and the positively charged anion-exchange functional groups.

Experimental Investigation on the Impact of Sulphate and Chloride on High Volume Fly Ash Concrete

High weathering action in the corrosive and chemically active environment can significantly affect the strength characteristics of the concrete and also excessive utilization of sand as fine aggregates in building construction enhances degradation of the environment and urges the need for an alternative source in the scene of sustainable construction. Fly ash has generally used an alternative of cement, such as an admixture in concrete, and production of cement. As per the literature it has been found that concrete containing fly ash as partial to complete replacement of fine aggregate has been found to increase strength on a long-term basis. An experimental investigation was carried out to evaluate the strength and durability characteristics of concrete building blocks by replacing fine aggregates with fly ash at 10% to 100% by weight of fine aggregate and subjecting it to chloride attack and sulfate attack. Various tests were conducted for the properties of fresh concrete. Compressive strength and flexural strength were determined at 28 days. Test results indicate significant improvement in strength properties of plain concrete by the inclusion of fly ash as partial replacement of fine aggregate (sand), and increase in resistance to sulfate and Chloride attacks and can be effectively used in structural concrete.

Removal of copper from sulfate solutions using biochar derived from crab processing by-product

Increasing metal demand is accelerating the mining and processing of minerals, however to ensure sustainable growth innovative approaches are required to better manage associated effluents. Biochar from the fast pyrolysis of residues from fishery and forestry operations has been studied as a low-cost, environmentally and economically friendly method for treating mine tailings and processing effluents. However, the bulk of the studies focus on terrestrial biomass (e.g. wood) and do not include potential inhibition/enhancement of adsorption due to pH controlling compounds. In this work biochar generated from snow crab (Chionoecetes Opilio) processing was studied as an adsorbent for copper solutions containing sulfate (a key compound in sulfide ore mining waters) with the objective of assessing adsorption capacity and the impact of sulfate on copper adsorption. The biochar, a porous structure comprised of calcite (CaCO3), was alkaline and has a negative zeta potential under neutral and basic conditions. The crab biochar removed over 99% of Cu2+ from a 100 mg/L solution (sourced as CuSO4) at a dosage of 5 g/L, which was higher than lignocellulosic biochar at the same biochar dosage. While metal adsorption can often be impacted at acidic conditions, Cu2+ adsorption was not impacted by initial acidic pH due to the biochar's buffering capacity. The Pseudo-Second Order (PSO) model fit the adsorption rate with maximum adsorption achieved in approximately 2 h. The maximum adsorption isotherm capacity was 184.8 ± 10.2 mg/g for Cu2+, much higher than existing commercial activated carbons and previously studied lignocellulosic biochars and followed the Freundlich isotherm. The adsorption mechanism responsible for removal of Cu2+ was found to be precipitation, in the form of the mineral posnjakite (Cu4[(OH)6SO4]·H2O). These results indicate for the first time that crab-based biochars are capable of adsorbing large quantities of Cu2+ from sulfate-rich solution, while also buffering solution pH, demonstrating promise as an acid mine drainage treatment for removal of harmful metals and reduction of acidity.

The impact of sulfate- and sulfide-bearing sand on delayed ettringite formation

With the increase of aggregate quarrying to meet the growing need for concrete construction comes a risk associated with new aggregate sources, which may not have uniform compositions and contain potentially harmful substances, such as sulfate and sulfide. To provide insights into the impact of sulfate- and sulfide-bearing sand on susceptibility to delayed ettringite formation (DEF), this study measures the evolution of expansion, acoustic nonlinearity (representing microscale damage), and dynamic elastic modulus of mortars prepared with varying cement compositions and exposed to an early-age high-temperature curing cycle. Samples containing sulfate- and sulfide-bearing sand show substantially higher initial levels of damage, with expansion starting at earlier ages than control samples. Damage in mortars using this sand can be attributed to accelerated decomposition of alkali-feldspar, microcracking due to relative thermal deformation between phases, early release of alkali that increases the amount of sulfate in the pore solution, and release of sulfate ions from aggregates.

Time dependent zero valent iron oxidation and the reductive removal of pertechnetate at variable pH

Elemental iron Fe0 is a promising reductant for removal of radioactive technetium-99 (Tc) from complex aqueous waste streams that contain sulfate, halides, and other inorganic anions generated during processing of legacy radioactive waste. The impact of sulfate on the kinetics of oxidation and reduction capacity of Fe0 in the presence of Tc has not been examined. We investigated the oxidative transformation of Fe0 and reductive removal of TcO4- in 0.1 M Na2SO4 as a function of initial pH (i.e., pHi 4, 7, and 10) under aerobic conditions up to 30 days. Tc reduction was the fastest at pHi 7 and slowest at pHi 10 (Tc reduction rate pHi 7 > 4 > 10). Aqueous fraction of Tc was measured at 0.4% at pHi 7 within 6 h, whereas ≥ 97% of Tc was removed from solutions at pHi of 4 and 10 within 24 h. Solid phase characterization showed that magnetite was the only oxidized crystalline phase for the first 6 h regardless of initial pH. Lepidocrocite was the most abundant oxidized product for pHi 10 after 5 days, but was not observed at pH of 4 or 7.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m ≤ 12 (with pH m = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

Comprehensive resistance of fair-faced concrete suffering from sulfate attack under marine environments

The fair-faced concrete structures serving in coastal areas may be harassed by sulfate ions carried by salt fog and rainwater. To explore the sulfate resistance performance of fair-faced concrete used in coastal subway station, specimens were subjected to simulated sulfate attack condition and actual marine environments in this study. The sulfate resistance properties of fair-faced concrete and the impact of sulfate on surface quality were investigated through compressive strength test, sulfate concentration distribution test, and the gray values of surface morphology characterization. The results show that the reminding residual strength of all specimens is still very high after exposed to simulated sulfate attack condition, demonstrating the superior sulfate resistance of fair-faced concrete used in coastal subway. Moreover, the sulfate corrosion can lead to the significantly coarsening of surface morphology, and the fair-faced concreted used in marine environments should pay special attention to sulfate corrosion. Besides, the coarse degree decreases with sulfate resistance coefficient, which means that fair-faced concrete with superior sulfate resistance can not only guarantee durability, but detain the degradation of surface morphology.

Strength and Swell Performance of High-Sulphate Kaolinite Clay Soil

Expansion of soils has been found to produce significant negative economic and environmental impact on various civil engineering infrastructure. This impact is more deleterious in soils containing sulphates, when treated with calcium-based stabilizers such as Lime and/or Portland cement (PC). The reported study investigated the strength and swell characteristics of Kaolinite clay artificially induced with high levels of Gypsum (sulphate) contents after stabilization with CEM I (PC), which is a calcium-based stabilizer. An optimum stabilizer content/Gypsum dosage, aimed at investigating the maximum magnitude of expansion possible using high levels of 10, 15 and 20% Gypsum contents (4.7, 7 and 9.3 wt.% sulphate) stabilized with calcium-based content of 7, 8, 9 and 10 wt.%. This was expected to provide further understanding on the mechanisms behind high sulphate-bearing clay soils, and the impact of sulphate and calcium content on strength and swell characteristics. The research outcomes showed that the introduction of sulphate to a Kaolinite clay soil reduces the compressive strength of the stabilised product by a factor range of 6–47% at 28 days curing age, while the swell behaviour is mainly dependent on both the sulphate content and curing age. Furthermore, the observed result suggests an 8 wt.% binder content to produce maximum magnitude of expansion (swell) with a high Gypsum content of 10% by weight. This finding is of economic importance, as it is expected to serve as a benchmark for further research on the stabilized clay systems, at high sulphate levels using sustainable binder materials.

Impact of sulfate and iron oxide on bacterial community dynamics in paddy soil under alternate watering conditions

Sulfate and iron oxides are often used as amendments in paddy soil, but their ecological risks for soil microbiomes are not well understood. Paddy soil amended with gypsum or hematite was incubated in laboratory microcosms under submerged (56 d) and subsequent dry (35 d) conditions. The soil bacterial community composition stabilized after 15–21 d of submergence and remained largely unchanged after redrying. The presence of OTUs related to facultative anaerobic bacteria (mainly Acidobacteria groups 7 and 16, Gemmatimonas, and unclassified bacteria) probably accounted for the limited variation in community composition after redrying, as suggested by random forest regressions. Redrying caused remarkable changes in the relative abundance of many bacteria putatively involved in soil reduction and oxidation. Gypsum and hematite did not stimulate sulfate or iron reduction after soil submergence. Although gypsum and hematite largely preserved the bacterial community composition, they significantly reduced the abundance and diversity of the total bacteria (by 3–12%), as well as the relative abundance of many putative bacterial reducers and oxidizers (by 17–100%), compared to the control. The results suggested the potential hazardous effects of sulfate and iron oxide on the bacteria in paddy soil, which should be considered before applying these amendments.

Biomethane recovery from source-diverted household blackwater: Impacts from feed sulfate

Biomethane recovery from source-diverted blackwater through anaerobic digestion (AD) offers a sustainable alternative for modern wastewater treatment. Water-wasting conventional toilets consume great amounts of flushing water (9L per flush), which results in blackwater with chemical oxygen demand (COD) of 1006 (±61) mg/L and COD/sulfate ratio of 12.2 (±0.9). In this study, the conventional toilets collected blackwater was treated through an up-flow anaerobic sludge blanket (UASB) reactor at 35°C with a hydraulic retention time (HRT) of 2.2 days, which achieved a COD removal efficiency >80 %. Inhibition in blackwater methanogenesis was observed, which was found associated with the growth of hydrogen utilizing sulfate reducing bacteria (SRB) that competed with hydrogenotrophic methanogens and suppressed the biomethane recovery efficiency. The sludge specific hydrogenotrophic methanogenic activity (SMA [H2&CO2]) increased from 0.37 (±0.02) g CH4-COD/g volatile suspended solids (VSS)/d (treating high sulfate blackwater) to 0.52 (±0.00) g CH4-COD/g VSS/d (treating low sulfate blackwater) when sulfate-free toilet flushing water was adopted (resulting COD/sulfate ratio of 42.9 [±5.0]). This study underlines the importance of considering the impact of sulfate on blackwater methane production when designing future blackwater treatment processes.

Synthesis of oligosaccharides of the linkage region of proteoglycans using regioselective glycosylation.

Proteoglycans (PGs) are complex macromolecules that are composed of glycosaminoglycan (GAG) chains covalently attached to a core protein through a tetrasaccharide linker. Biosynthesis of PGs is complex and involves a large number of glycosyltranferases. We report herein for the first time the synthesis of a collection of various sulfoforms of the disaccharide GlcA-1,3-β-d-Gal and trisaccharides GlcNAc-1,4-α-d-GlcA-1,3-β-d-Gal and GalNAc-1,4-β-d-GlcA-1,3-β-d-Gal using a regioselective glycosylation. Preliminary results on the impact of sulfation of these disaccharides upon recombinant chondroitin sulfate N-acetylgalactosaminyltransferase-1 (CSGalNAcT-1) involved in chondroitin sulfate chain initiation is also reported.

Bioelectrochemical treatment of groundwater containing BTEX in a continuous-flow system: Substrate interactions, microbial community analysis, and impact of sulfate as a co-contaminant

Microbial electrochemical technologies (MET) are increasingly being considered for in situ remediation of contaminated groundwater. However, their application potential for the simultaneous treatment of complex mixtures of organic and inorganic contaminants, has been only marginally explored. Here we have analyzed the performance of the ‘bioelectric well’, a previously developed bioelectrochemical reactor configuration, in the treatment of benzene, toluene, ethyl-benzene and xylenes (BTEX) mixtures. Although to different extents, all BTEX were found to be degraded in the bioelectrochemical system, operated using a continuous-flow of groundwater at a hydraulic retention time of 8.8 h, with the graphite anode potentiostatically controlled at +0.200 V vs. the standard hydrogen electrode. In the case of toluene and ethyl-benzene, biodegradation was further confirmed by the GC–MS identification of fumarate-addition metabolites, previously shown to be involved in the activation of these contaminants under anaerobic conditions. Degradation rates were higher for toluene (31.3 ± 1.5 mg/L d) and lower for benzene (6.1 ± 0.3 mg/L d), ethyl-benzene (3.3 ± 0.1 mg/L d), and xylenes (4.5 ± 0.2 mg/L d). BTEX degradation was linked to electric current generation, with coulombic efficiencies falling in the range 53–69%, although methanogenesis also contributed to contaminant degradation. Remarkably, the system also allowed removal of sulfate simultaneously with toluene. Sulfate removal was likely driven by the hydrogen abiotically generated at the cathode. Taken as a whole, these findings highlight the remarkable potential of this innovative reactor configuration for application in a variety of contamination scenarios.

Influence of sulfate on the chloride diffusion mechanism in mortar

The deterioration of cement based materials in marine and salts lakes environment is complicated problem, due to the presence of chlorides and sulfate simultaneously. The influence of sulfate on the chloride diffusion mechanism was evaluated by scanning electron microscopy (SEM-EDS), mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD). The total chloride profile was also used to illustrate the influence of chloride and sulfate salts concentrations on chloride diffusion. The results show that the chloride binding and formation of Friedel’s salt are inhibited by the presence of sulfate. The presence of sulfate increases chloride diffusion in the short term, while it inhibits the chloride diffusion from a long-term perspective. The aggressive ions penetrate into the mortar causing mortar’s porosity decrease, especially the pore <50 nm, which means the sulfate inhibits the chloride ions diffusion. The impact of sulfate on the chloride ions diffusion mechanism depend on chloride and sulfate salts concentrations, exposure time and diffusion depth. This study can provide a better insight for understanding the deterioration of cement-based materials under chloride-sulfate compound salts attack.

Impact of sulphate and heavy metals release on household portable water in Nigeria

The paper attempts frequent hitches regarding household portable water in Nigeria. It enlighten both end user and portable water providers about the heavy metals potential discharge that pre-accumulate in iron corrosion scales as it poses an contaminants health threat when released into household portable water. Likewise offers conjectural knowledge about formation, main uses, health effects of both heavy metals and sulphate on human for example arsenal causes immunotoxic, zinc creates abdominal pain etcetera besides common methods for removing both sulphate and heavy metals like distillation or reverse osmosis for small water and ion exchange for large water quantities because chemical reaction between sulfates and heavy metals discharge from portable water distribution system can affect the water quality by decreasing or oxidizing the heavy metals in the water therefore, awareness about the impacts of sulfate on heavy metals release from portable water distribution system is required . Also users and portable water provider must develop habit of testing portable water from consumer tap because despite water quality parameters of the finished water reached portable water healthy standards from water distribution system nonetheless the tap water which the customers exactly exploited could be infected, since the portable water undertake an extensive Hydraulic Retaining Period (HRP) of storing and transference in water distribution systems.

Metabolism of Curcumin in Human Breast Cancer Cells: Impact of Sulfation on Cytotoxicity.

Curcumin is a natural polyphenol with promising anticancer properties that undergoes pronounced metabolism in humans. In order to determine whether metabolism of curcumin also occurs in tumor cells and whether biotransformation has any impact on cytotoxicity, metabolism experiments were conducted with hormone-dependent ZR-75-1 and hormone-independent MDA-MB-231 human breast cancer cells. By using HPLC-ESI-Qq-TOF-MS, it was possible to identify one main metabolite, namely curcumin sulfate, in both cell lines. Its concentration in the cytoplasm and culture medium was 1.6- to 1.7-fold higher in ZR-75-1 cells than in MDA-MB-231 cells, concomitant with a 2-fold higher IC50 value in the ZR-75-1 cell line (14 µM compared to 7.3 µM). The net result of sulfation seems to lower the intracellular concentration of curcumin, thereby decreasing its growth inhibitory activity. Interestingly, for the first time, we also found the formation of a curcumin dimer in the cytoplasm but not in the cellular medium of both cell lines. Compared to curcumin sulfate, however, its maximal intracellular concentrations were up to 4-fold lower, indicating only a minor contribution to the overall curcumin clearance. In conclusion, our data elucidated the metabolism of curcumin in breast cancer cells, which must be considered in humans following oral uptake of dietary curcumin as a chemopreventive agent.