Visible Light Irradiation Conditions Research Articles

Enhanced photo-assisted thermal catalytic oxidation of formaldehyde via abundant surface adsorbed oxygen in Co3O4 with the assistance of natural zeolite

Photo-assisted catalytic oxidation is a promising and sustainable method for the formaldehyde (HCHO) degradation. Catalyst loading and surface adsorbed oxygen species are common strategies to enhance the efficiency of photo-assisted catalytic oxidation. In this work, acid-treated zeolite-based natural zeolites (mordenite and stellerite) were used as supports, to obtain Co3O4-natural zeolite composites by impregnation and MOF-templated methods. Under the combined action of visible light irradiation and heat condition, the photo-assisted thermal catalytic performance of different composites was determined. Among these composites, the Co-AS (Co3O4-acid-treated stellerite) composite exhibited the best HCHO mineralization performance. The use of acid-treated stellerite as a catalyst carrier effectively reduced the crystallite size of Co3O4, improved its dispersibility, and increased the surface adsorbed oxygen species, contributing to enhanced catalytic efficiency. The in-situ DRIFTs results showed that the main intermediates of photo-assisted thermal catalysis degradation were dioxymethylene (DOM) and HCOO-. Additionly, the reusability performance of the composites was also investigated. Experimental results showed that the composite had good photo-assisted thermal catalytic performance and durability, making it a promising catalyst for indoor air purification.

Terminalia catappa leaf extract as a bio-reducing agent to synthesize Cu2O nanoparticles for methylene blue photodegradation

The large tree species Terminalia catappa is a member of the Combretaceae family and is mainly found in tropical climates. They are commonly cultivated for shade because they have huge, dense foliage. Numerous polyphenols, including flavonoids, tannins, saponins, and phytosterols, are present in the leaves. In this study, the green chemical method was used to extract polyphenols from dried green almond leaves. They were employed in the synthesis of Cu2O nanoparticles as a reducing agent. FTIR and UV–Vis were used to describe the leaf extract of Terminalia catappa after the chlorophyll was removed. Copper salt was used to create Cu2O nanoparticles via a reduction process. The extract's potential for photocatalytic dye degradation has also been explored. The obtained Cu2O had a spherical shape with dimensions of 50–100 nm, and its band gap energy reached 1.945 eV to remove methylene blue from aqueous media under visible light irradiation conditions. At an initial MB concentration of 10 ppm, the decomposition efficiency reached 71.99% after only 2 h of exposure to simulated sunlight. The decomposition process occurred according to a pseudo-first-order kinetic model with a rate constant of 0.0084 min−1.

A high-efficiency clay mineral based organic photocatalyst towards photodegradation of butyl xanthate in mineral processing wastewater

The organic solar cell active layer, well known for excellent visible light response capability, is regarded as a potential candidate for photocatalytic degradation of organic wastewater. However, the poor dispersibility in water due to its hydrophobicity property severely limited the degrading efficiency. In this work, a novel composite photocatalyst PM6:IDT8CN-M/CK2 with a broad visible absorption spectrum and non-toxicity was first synthesized through the intercalation compounding method. A good dispersibility of PM6:IDT8CN-M in wastewater was achieved with the help of rich interlamellar porosity and good hydrophilicity of calcined kaolin. This composite photocatalyst was successfully applied to the SBX photocatalytic degradation in mineral processing wastewater, and the SBX pollutants can be completely degraded within 10 min under the condition of visible light irradiation. Compared with other reported photocatalysts, the photocatalytic degradation efficiency of SBX was dramatically improved by at least seven times. Moreover, PM6:IDT8CN-M/CK2 has remarkable stability, sustaining degradation efficiencies of over 90 % in 60 cycles. Notably, the organic solar cell active layer in PM6:IDT8CN-M/CK2 can achieve carrier rapid separation and transport, enhancing the generation of active oxides (∙O2–, and ∙OH, etc.). At the same time, the large surface area of PM6:IDT8CN-M/CK2 provides a suitable environment for the oxidation reaction of active radicals with SBX to achieve this efficient photocatalytic degradation. Overall, this work not only extends the application scope of organic solar cell active layer, but also develops a high-efficiency SBX removal technique for the treatment of mineral processing wastewater.

Synthesis of Acyl Cyclopentaquinolinones through Simultaneous Construction of the Heterocyclic Scaffold and Introduction of the Acyl Group.

Presented herein is an effective and concise synthesis of acyl cyclopentaquinolinone derivatives via the cascade reactions of N-(o-ethynylaryl)acrylamides with α-diazo carbonyl compounds. The formation of product involves a visible light-induced radical formation from α-diazo carbonyl compound followed by its addition onto the acrylamide moiety to trigger double radical annulation, single-electron oxidation, and β-elimination. To our knowledge, this is the first example in which the cyclopentaquinolinone scaffold was constructed along with the introduction of an acyl group under visible light irradiation conditions. Compared with literature methods for similar purpose, this newly developed protocol has advantages such as readily accessible substrates, mild reaction conditions, valuable products, concise synthetic procedure, and high sustainability. With all these merits, this method is expected to find wide applications in the construction of related acyl heterocyclic skeletons.

The visible optical driving N-S co-doped La2Ti2O7 activated peroxydisulfate for carbamazepine removal: Mechanism and performance

Carbamazepine (CBZ) as an “emerging pollutant”, which poses a threat to human health. Photocatalytic activation of peroxydisulfate (PDS)-based advanced oxidation processes (AOPs) can deep oxidation of CBZ pollutants through the generation of free radicals with high redox potential. However, most of common photocatalysts only have a narrow band gap, which limits their application under visible light. In order to broaden the band gap of photocatalysis, herein we report the N-S co-doping in La2Ti2O7 (N-S LTO) is viable, and then evaluate the visible light activation of PDS to remove the pollutants of CBZ. Compared with pure LTO and N or S mono-doped LTO, the degradation efficiency of CBZ in N-S LTO/PDS/Vis system was 2.18, 1.45, and 1.41 times improved, respectively, under the visible light irradiation condition. Furthermore, the mechanism of CBZ degradation under N-S LTO/PDS/Vis processes was explored and revealed that the HO• and SO4•− were the main substances for the breakage of CBZ molecules. The further physicochemical characterization of samples convinced the active sites in N-S LTO for PDS motivation and oxidation processes with the best separation and migration ability of carriers than other samples. Finally, combined with density functional theory (DFT) calculations, the detailed degradation pathways of CBZ were proposed. This work not only provides insight into the construction of photocatalysts with co-doping for PDS activation, but also brings an inspiration of CBZ degradation in water treatment.

Carbon layer derived carrier transport in Co/g-C3N4 nanosheet junctions for efficient H2O2 production and NO removal

Co nanoparticles are embedded in N-doped carbon nanotubes (Co-N-carbon nanotubes) using combinations of mechano-chemical pre-treatment and thermal polymerization process (at 760 °C). A further thermal polymerization process done on these Co-N-carbon nanotubes and ultrathin graphitic carbon nitrate (g-C3N4) leads to the formation of Co nanoparticles (coated with carbon layers) embedded g-C3N4 nanosheets composite, along with the disappearance of carbon nanotube morphology on the material. The Co/g-C3N4 junctions are constructed with a Schottky barrier formed between the carbon layer coated Co nanoparticles and the g-C3N4 nanosheets. The presence of carbon layers in the composite system facilitates transport of photogenerated electrons at the Fermi level of Co, which results in enhanced photocatalytic H2O2 generation and NO oxidation performances of the composite material in visible light irradiation condition with excellent cyclic stability. The Schottky junction composites constructed using optimized preparation conditions in case of no co-catalyst incorporation shows a photocatalytic H2O2 generation efficiency of 3618 μmolL−1h−1 which is about 1000 times of that of pristine g-C3N4 nanosheets. A NO removal rate of 62 % (higher than that of the commercial P25 (TiO2)) is also observed. These results provide possible approaches on constructing advanced photocatalysts for energy and environmental applications.

Unveiling the charge migration-induced surface reconstruction of Cu2MoS4 catalyst for boosted CO2 reduction into olefiant gas

Understanding the charge dynamic behavior of the catalyst is crucial to unravel the underlying mechanism for photocatalytic CO2 reduction to C2+ products. However, the structure–activity relationships are not intuitive because of the dynamic evolution of electronic and atomic structures for catalysts under the excitation state. Herein, modeling on layered Cu2MoS4 nanosheets, we for the first time observe charge migration-induced evolution of electronic and atomic structure on Cu2MoS4 catalyst during the CO2 reduction process by combining synchronous-illumination X-ray photoelectron spectroscopy (SI-XPS) with X-ray diffraction (SI-XRD). During the dissociation of CO2 molecules as well as the charge migration process under the visible light irradiation condition, the surface S atoms return back to the lattice phase, leading to the valence-state normalization of Cu, Mo and S atoms and the increases of the interlayer lattice spacing. By virtue of the above unique characteristic changes, Cu2MoS4 nanosheets exhibit excellent activity enhancement (8.7 μmol g−1 h−1) for CO2 reduction to C2H4 under the visible light irradiation in comparison with the trace amount of Cu-doped MoS2 and pure MoS2.

Visible-light-promoted photoredox-catalyzed N-aminoalkylation of quinazolinones with simple alkylamide

A metal free visible-light promoted direct coupling of simple alkylamides and quinazolinones via CH bond oxidative cross-coupling to access highly functionalized N-aminoalkyl quinazolinones was reported. This protocol serves as a straightforward strategy for N-aminoalkylation transformation of quinazolinones employing tert-butyl peroxybenzoate as oxidant under visible-light irradiation condition. This process features metal-free, mild reaction conditions and the tolerance for a wide range of functional groups. Synthetically important and highly functionalized N-aminoalkyl quinazolinones were afforded with moderate to good yields and high chemoselectivity.

Photocatalytic dye degradation using lithium borate-bismuth tungstate glass-ceramics

The disposal of wastewater contaminated with dyes is a prevalent global concern that necessitates the implementation of diverse remediation strategies. There are several methods available for the treatment of wastewater, one of which is photocatalytic treatment. The primary objective of this study is to assess the efficacy of a lithium borate-bismuth tungstate glass-ceramic material (0.7Li2B4O7 - 0.3Bi2WO6) in the degradation of methylene blue dye through photocatalysis under visible light irradiation conditions. The glass under consideration was prepared using the conventional melt-quench technique. The characterization of the glass was conducted using X-ray diffraction technique and Raman spectroscopy. Additionally, the glass obtained was subjected to various heat treatments in order to achieve crystallization, as assisted by differential scanning calorimetry as reported. The elemental analysis and morphology of the glass ceramics that were prepared were examined using X-ray photoemission spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). The glass-ceramic sample exhibited a dye degradation efficiency of 73% within a time span of 240 min. The evaluation of the active species involved in degradation is also conducted through the utilisation of a scavenger test. The experiments were conducted multiple times to verify the effectiveness of the prepared glass-ceramic material for water purification purposes.

Photoinduced Reaction of α‐Bromoacetophenone with Thiosulfonate: Synthesis of β‐Keto Thiosulfone

AbstractA photoinduced synthesis of β‐keto thiosulfone/β‐keto selenosulfone by the reaction of α‐bromoacetophenone with thiosulfonate/selenosulfonate under metal‐free and visible light irradiation conditions is developed. Two C−S bonds or one C−S bond and one C−Se bond were constructed simultaneously.

Engineering oxygen vacancies of 2D WO3 for visible-light-driven benzene hydroxylation with dioxygen

Solar-driven benzene oxidation with dioxygen (O2) provides a green and sustainable alternative for phenol production, but the construction of heterogeneous photocatalysts remains a huge challenge for efficient conversion under visible light irradiation and ambient conditions. Herein, we reported a facile microwave assisted strategy for the defect engineering of two-dimensional (2D) tungsten oxide while well maintaining the original crystalline architecture. Abundant oxygen vacancies were constructed on the 2D tungsten oxide, which remarkably promoted photochemical (light harvesting, charge separation and transfer) and O2 activation behaviors, this promotion effect was further strengthened by the hybridization with Pt species with the formation of Schottky junction. The champion catalyst enabled a high phenol yield of 11.3% with a selectivity of 91% in the visible-light-driven benzene hydroxylation with atmospheric O2 at room temperature. The catalyst can be facilely recovered and reused with stable activity. The oxygen vacancies and Pt co-catalyst were demonstrated to play vital roles in the photocatalytic formation of the reactive oxygen species (hydroxyl radials, ·OH) for effective oxidation.

Photocatalytic degradation of organic dyes on magnetically separable barium hexaferrite as photocatalyst under conditions of visible light irradiation

In this paper, we present the first attempt to evaluate the role of carboxymethyl cellulose (CMC) as a chelating agent in the sol-gel auto-combustion method of producing barium hexaferrite (BaFe12O19). We also report the application of the system as a photocatalyst for dye degradation. The formation, morphology, and crystalline structure of the synthesized nanoparticles are determined using XRD, SEM, EDS, VSM, FTIR, and TEM techniques. High efficiency under visible light, with a band gap of 1.62eV and a BET surface of 17.93 m2/g, has been observed for the BaFe12O19 catalyst. The operating parameters, such as reaction time, initial dye concentration, light intensity, reusability, and dye type, are studied. Degradation rates as high as 98.26% (Kapp = 0.082min-1) and 89.07% (Kapp = 0.0743min-1) were obtained for cases of methylene blue and malachite green under conditions of visible light irradiations when BaFe12O19 was used. The BaFe12O19 catalyst has been shown to exhibit a high degradation performance for cationic dyes. Furthermore, BaFe12O19 magnetic nanoparticles show excellent reusability for dye degradation because the photocatalyst did not exhibit a significant decrease in its activity even after five runs (81.56%). As a result, the current study confirmed that photocatalytic degradation was a promising technology for saving water and treating wastewater formed from textile dye industries. The technique can be used to study the efficiency of photocatalytic degradation and understand the process of recycling waste effluents under conditions of minimized water use.

Adjacent diatomic Cu1N3/Mo1S2 entities decorated carbon nitride for markedly enhanced photocatalytic hydrogen generation

The regulation of the electronic structure of graphitic carbon nitride (CN) has been considered as one of the most promising methods to improve its photocatalytic efficiency. However, how to adjust effectively the electronic structure remains a great challenge. Herein, we pioneered a microwave-assisted solvothermal sulphidation strategy for the preparation of Cu1N3-linked Mo1S2 adjacent diatomic entities decorated CN (Cu1N3/Mo1S2/CN) through the enabled sulphidation around single Cu atom by the super hot spots owing to the localized surface plasmon resonance effect. The electronic structure of CN is regulated by the synergistic effect of the adjacent diatomic metal Cu and Mo, which not only makes the conduction band of the catalyst closer to the Fermi level, but also improves the charge transfer of CN. As a result, Under visible light irradiation and atmosphere conditions, the H2 generation rate (HER) of the Cu1N3/Mo1S2/CN catalyst reaches as high as 6.14 mmol g-1h−1, which is 85 times higher than that onbulk CN. It was highlighted that the introduced Cu1N3-linked Mo1S2 adjacent diatomic entities act as modulator to efficiently tune the electronic structure of the CN semiconductor, rather than as active sites, and for all samples, the deposited Pt is requested to act as active sites for H2 production. This work not only provides enlightenment for the development of an outstanding non-precious metals modified CN-based photocatalyst for solar hydrogen production, but also provides a new avenue for the design of diverse adjacent diatomic catalysts towards various transformations.

Green Synthesis and Characterizations of Cobalt Oxide Nanoparticles and Their Coherent Photocatalytic and Antibacterial Investigations

Water pollution is a serious concern for developing and undeveloped countries. Photocatalytic degradation of organic pollutants is an effective degradation method to restrain the green ecosystem. This research article presents a green, low-cost, and benevolent eco-friendly biosynthesis of cobalt oxide (Co3O4) nanoparticles using Curcuma longa plant extract. The UV and visible region absorbance of Co3O4 nanoparticles estimated the Co2+ and Co3+ transitions on the lattice oxygen, and their bandgap of 2.2 eV was confirmed from the UV-DRS spectroscopy. The cubic structure and spherical shape of Co3O4 nanoparticles were estimated by using XRD and TEM characterizations. Plant molecules aggregation and their agglomerations on the nanoparticles were established from FTIR and EDX spectroscopy. Multiple cobalt valences on the oxygen surfaces and their reaction, bonding, and binding energies were analyzed from XPS measurements. The biogenic Co3O4 nanoparticles were executed against gram-positive (Staphylococcus aureus—S. aureus) and gram-negative (Escherichia coli—E. coli) bacteria. A gram-positive bacterial strain exhibited great resistivity on Co3O4 nanoparticles. Degradation of organic dye pollutants on the Co3O4 nanoparticles was performed against methylene blue (MB) dye under the conditions of visible light irradiation. Dye degradation efficiency pseudo-first-order kinetics on the pseudo-first-order kinetics denotes the rate of degradation over the MB dye. This research work achieved enhanced degradation potency against toxic organic dye and their radicals are excited from visible light irradiations. Absorption light and charged particle recombinations are reformed and provoked by the plant extract bio-molecules. In this process, there is no inferior yield development, and electrons are robustly stimulated. Furthermore, the biosynthesized Co3O4 nanoparticles determined the potency of bacterial susceptibility and catalytic efficacy over the industrial dye pollutants.

Cobalt-doped double-layer α-Fe2O3 nanorod arrays for enhanced photoelectrochemical reduction of Cr(VI)

Element doping is an important method for improving the performance levels of photoelectrochemical (PEC) cells. Nevertheless, to date, the PEC conversion efficiency and photocurrent characteristics of the available photoanodes remain very low. In this study, cobalt (Co) was selectively doped into the bottom and/or top layers of double-layered α-Fe2O3 nanorod arrays grown on conductive transparent substrates (F:SnO2, FTO) via a two-step hydrothermal method; this process was performed to enhance the charge transfer ability and thus significantly improve the PEC performance. The light response capabilities of all α-Fe2O3 films were evaluated by an electrochemical workstation under dark or visible light irradiation conditions. The sample of Co doped in the bottom layer exhibited a high photoelectrochemical performance, achieving a current density of 1.37 mA/cm2 at + 1.0 V versus saturated calomel electrode (SCE); additionally, the sample exhibited a photoelectric synergistic ability to reduce Cr(VI) in an aqueous solution, with 84.85% reduction in 180 min. Under the influence of the electric field inside the double-layer electrode, the photoexcited electrons and holes are transferred to the surfaces of the FTO substrate and the photoanode, increasing the current density and enhancing Cr(VI) reduction. The results of this study offer an alternative approach for designing novel photoanodes with improved PEC performance levels by engineering the electron density distribution and band structure for efficient carrier separation; the results may provide new solutions in heavy metal reduction and contaminant degradation projects.

Amino-cobalt(II)phthalocyanine supported on silica chloride as an efficient and reusable heterogeneous photocatalyst for oxidation of alcohols

The selective photocatalytic oxidation of alcohols is considered as a valuable process in order to produce aldehydes and ketones. In the present study, novel heterogeneous and recoverable cobalt (II) phthalocyanine (CoPc) was designed and synthesized through a covalent binding between an amino-cobalt (II) phthalocyanine on the surface of silica, and named as TACoPc/Si-Cl. This catalyst was fully characterized using IR, X-ray diffraction patterns (XRD), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), element analysis (CHN), and ultraviolet–visible spectroscopy (UV/Vis). Various reaction parameters such as catalyst amount, temperature, time, solvent and amount of oxidant were investigated in the oxidation of primary and secondary alcohols to the corresponding carbonyl compounds. The desired products were obtained with acceptable efficiency and selectivity of over 98%, under visible light irradiation conditions. The supported catalyst exhibited a higher reactivity than the unsupported and after the reaction comes off easily and reusable. The recovered catalyst was reused six times. The obtained results show that the stability, efficiency and selectivity of described catalyst have not changed much compared to the fresh catalyst.

Palladium‐Modified TiO2/MWCNTs for Efficient Carbon Capture and Photocatalytic Reduction of Nitro‐aromatic Derivatives

AbstractIn this study, modified TiO2 nanocomposites with the noble metal (Ag or Pd) followed by dispersion on multiwall carbon nanotubes (MWCNT) were synthesized and applied in the photocatalytic oxidation of CO at room temperature in the absence of oxygen. The results revealed that the highest active photocatalyst was Pd/TiO2/MWCNT towards CO and p‐nitrophenol (PNP) conversion. The reaction was dependent on the catalyst loading, concentration of tert‐butyl ammonium bromide (TBAB) as co‐catalyst and the reaction time as well as the temperature of their reduction. It was found that the optimal condition for PNP transformed into p‐aminophenol (PAP) and formic acid (HCOOH) was the use of 0.05 wt % of Pd/TiO2/MWCNT nanocatalyst, 2 mol % of TBAB under visible light irradiation condition at room temperature after 1 hour. The as‐prepared photocatalysts were fully characterized using Scanning electron microscope (SEM‐EDX), high resolution transmission electron microscope (HR‐TEM), X‐ray diffraction (XRD) and Brunauer‐Emmett‐Teller (BET). In addition, the band gaps of TiO2 nanoparticles, TiO2/MWCNT and Ag‐ or Pd‐modified TiO2/MWCNT nanocomposites were calculated from diffuse reflectance spectroscopic (DRS) analysis, ensuring the best photocatalytic efficiency. This approach is significantly beneficial for development of new generation of detoxification/transformation catalysts. The probable mechanism of photo‐oxidation of CO by H2O was postulated.

Construction of Fe3S4/g-C3N4 composites as photo-Fenton-like catalysts to realize high-efficiency degradation of pollutants

To perfect the photocatalytic performance of Fe3S4 under visible light irradiation using tetracycline hydrochloride (TCH) as a target contaminant, magnetic Fe3S4/g-C3N4 composites with a visible light response were synthesized by a one-step hydrothermal method. The effects of varying quality ratios, temperatures, pH value, and H2O2 concentrations on photocatalysis was investigated, and the composites were characterized by XRD, FTIR, XPS, SEM, etc. The results show that the highest photo-Fenton catalytic efficiency is obtained for a composite with a Fe3S4 to g-C3N4 quality ratio of is 1:0.75 (Fe1C0.75). More than 97.5% of TCH is removed by Fe3S4/g-C3N4/H2O2 within 60 min under visible light irradiation and near-neutral conditions (pH 6.2), and its first-order kinetic constant is determined to be 0.06802 min−1. The removal efficiency for Fe3S4/g-C3N4 is 1.61 and 13.34 times higher than that of the parent Fe3S4 and g-C3N4, respectively. At this time, g-C3N4 can effectively increase the leaching of S0. The effects of different active species in the TCH degradation experiment with the Fe1C0.75 composite were studied, and it is found that h+, ·O2−, and ·OH radicals are the main substances involved in the degradation of TCH. The synthesized Fe3S4/g-C3N4 catalyst is a promising heterogeneous photo-Fenton catalyst for the removal of organic pollutants.

Copper-catalyzed umpolung Sonogashira-type coupling of arene boronic acids under visible light.

We report herein that a copper catalyst catalyzed efficient cross-coupling of aryl and alkenyl boronic acids with alkynyl-1,2-benziodoxol-3(1H)-ones to afford diaryl alkynes and enynes under mild visible light irradiation conditions using a catalytic amount of base or even in the absence of base. The reaction applies copper as the catalyst and tolerates a variety of functional moieties including aryl bromide and iodide.

Effects of acid mine drainage on photochemical and biological degradation of dissolved organic matter in karst river water

Dissolved organic matter (DOM) can be removed or transformed by photochemical and biological processes, producing the negative effect of transforming organic carbon into inorganic carbon, which plays a vital role in the karst carbon cycle. However, acid mine drainage (AMD) will affect this process, so the degradation of DOM in karst river water (KRW) needs to be studied in this context. In this study, to reveal the evolution processes of DOM under photochemical and biological conditions in AMD-impacted KRW, AMD and KRW were mixed in different ratios under conditions of visible light irradiation (VL), biodegradation (BD), ultraviolet irradiation (UV) and ultraviolet irradiation + biodegradation (UV+BD). The average DOC concentrations in samples after mixing AMD and KRW in different proportions decreased significantly (by 23%) in UV+BD, which was 1.2–1.4 times higher than under the other conditions and would lead to a significant release of inorganic carbon. Further analysis of the fluorescence parameters via parallel factor analysis (PARAFAC) revealed that the DOM fluorescence components in AMD comprised mainly protein-like substances derived from autochthonous components, while the DOM fluorescence components in KRW were mainly humic-like substances with both autochthonous and allochthonous sources. Therefore, AMD could promote both the photochemical and biological degradation of DOM in karst receiving streams, resulting in the conversion of DOC to inorganic carbon. The results showed that the synergistic effects of UV+BD and AMD accelerated the degradation of DOM and the release of inorganic carbon in KRW, thus affecting the stability of the karst carbon cycle.