Photodegradation Of Humic Acid Research Articles

Photodegradation of humic acid from the surrounding soils of a sub-alpine Lake Tiancai

溶解性有机质（DOM）是湖泊生态系统的物质循环和能量流动的基础.典型亚高山湖泊DOM的主要来源为流域土壤腐殖酸（外源DOM），其具有较强的光吸收特性，光降解是其重要的转化过程，从而改变碳、氮、磷等物质的存在形式.在气候变暖的背景下，亚高山湖泊中DOM的浓度、pH、溶解氧及太阳辐射都可能发生变化；但这些环境变化对亚高山湖泊DOM光降解过程的影响尚不够清楚.由此本文研究了亚高山湖泊——天才湖（树线下200 m）周边土壤提取的腐殖酸（THA）的光降解过程：首先考察在光源为500 W汞灯、不通气以及pH=8.0条件下THA的降解过程中DOC浓度、有色溶解性有机质（CDOM，以a₂₈₀表征）和荧光溶解性有机质（FDOM）的变化，其后定性比较、定量分析不同光降解条件（pH、载气和光照波段）对THA的光降解过程的影响.结果表明，THA含有4种荧光组分，其中C1~C3均为类腐殖质，占总荧光强度83.64%，C4占比16.36%，为类蛋白质物质.在500 W汞灯的照射下，THA分子量逐渐降低，10 h后DOC浓度降低44.5%，a₂₈₀随光照时间的增加逐渐减少，CDOM含量较初始大幅度下降；而FDOM （以荧光组分强度表示）总体趋势表现为先增加后下降.相对于弱碱性的环境（pH=8.0），弱酸性环境（pH=6.0）更有利于THA的光化学过程.氧气的存在很大程度上促进了DOM光化学转化过程，通入空气的条件下a₂₈₀的降解速率是氮气条件下的3.25倍.在不同光波段的实验下表明，可见光和紫外光对THA降解的贡献差异较大，紫外光波段的表观光子降解率（η）约为可见光的5~11倍.结果表明在气候变化背景下，亚高山湖泊中DOM的光化学降解将可能加快，亚高山湖泊在碳循环中的作用可能增强.;Dissolved organic matter (DOM) in lakes is ubiquitous and plays an important role in the aqueous ecosystem. DOM in sub-alpine lakes is dominated by the terrestrially-derived humic acid in the soil. Photodegradation is an important transformation process of DOM because of its strong light absorption, changing the form of carbon, nitrogen, phosphorus. Under the scenario of climate warming, DOM concentration, pH, dissolved oxygen and solar radiation in subalpine lakes may change. However, the effects of these environmental changes on DOM photodegradation in sub-alpine lakes are still unclear. In this paper, the photodegradation of allochthonous DOM in a sub-alpine lake-Lake Tiancai (located 200 m below the tree line) were studied. Firstly, the humic acid (THA) was extracted from the soil around Lake Tiancai. Then the photodegradation of THA was investigated at different light bands (ultraviolet or visible light) and different pH conditions. The results showed that four components were identified by excitation-emission matrix fluorescence coupled with parallel factor analysis (EEM-PARAFAC), including C1-C3 were humic-like fluorescence, accounting for 83.64% of the total fluorescence intensity, and C4 was protein-like substance, accounting for 16.36%. Under the irradiation of 500 W mercury lamp, the molecular weight of THA decreased gradually and DOC concentration decreased by 44.5% after 10 h. The value of a₂₈₀ (a proxy for colored dissolved organic matter (CDOM)) decreased gradually with the irradiation time; while the fluorescent dissolved organic matter (FDOM) showed an overall trend of increasing at first and then decreasing. Compared with the weakly alkaline media (pH=8.0), the weakly acidic media (pH=6.0) facilitated for the photochemical process of THA and acidification may further promote DOM degradation. Oxygen played a crucial role in DOM photochemical reaction as the pseudo-first-order kinetic constant of a₂₈₀ in the presence of oxygen was 3.25 times that in the absence of oxygen. The ultraviolet light was much more efficient for THA degradation than visible light. The apparent quantum degradation ratios (η) of ultraviolet light were about 5-11 times that of visible light. This result of this study suggested that under the scenario of climate change, the photodegradation of DOM in sub-alpine lakes might accelerate, enhancing the role of sub-alpine lakes in the carbon cycle.

Kinetics of Humic Acids Photodegradation in Aqueous Solution Using TiO<sub>2</sub>/ ZnO/Co Composite Photocatalyst

Humic acid (HA) is a major component of natural organic substances and affects water quality, such as color, taste and odor. Therefore, removal of HA from surface water or wastewater is very important. In this paper, the photodegradation kinetics of these compounds using TiO2/ZnO/Co composite photocatalyst under visible light irradiation was investigated. The progress of photocatalytic degradation of the HA has been observed by measuring the absorbance in UV-Visible spectrophotometer. The results reveal that the TiO2/ZnO/Co composite photocatalyst exhibits much better photocatalytic activity than those of pure TiO2 and TiO2/ZnO on photodegradation of HA under visible light irradiation, with degradation rate constants were found 0.0163, 0.0079 and 0.0032 (min-1), respectively.

Monitoring Humic Acid Photodegradation by CUPRAC Colorimetric and HPLC Determination of Dihydroxybenzoate Isomers Produced From a Salicylate Probe

Novel analytical methods were designed for monitoring humic acid photodegradation in environmental waters. Modified CUPric Reducing Antioxidant Capacity (CUPRAC) spectrophotometric and chromatographic methods were used for the determination of dihydroxybenzoate isomers (DHBAs) produced from a salicylate probe, which was hydroxylated by hydroxyl radicals (•OH) produced from the photodegradation of humic acid under ultraviolet A-radiation. The combined use of CUPRAC colorimetry and HPLC was shown to effectively monitor humic acid photodegradation and •OH generation for the first time. The formation of 2,5-dihydroxybenzoate and 2,3-dihydroxybenzoate, as major and minor products, respectively, from the hydroxylation of a salicylate probe was demonstrated by HPLC and confirmed by a modified CUPRAC method to indicate •OH formation from humic acid, which acted as both a generator and absorber of hydroxyl radicals. Salicylate hydroxylation showed an increase between 30 and 50 min of illumination, and was affected by the initial concentration of humic acid up to 0.01% but not by solution pH around the neutral values. Traces of Fe(III) and Mn(II) present in natural waters decreased the •OH production, but EDTA partly restored the probe hydroxylation by chelating these metal cations. Since humic acid-mediated •OH generation may aid in natural disinfection processes, this work may extend our comprehension of concentration- and time-dependent generation of •OH in environmental waters and of the possible effects of other antioxidants.

Control of Membrane Fouling in Organics Filtration Using Ce-Doped Zirconia and Visible Light.

Membrane fouling has been a major issue in the development of more efficient water treatment processes. Specifically in surface waters filtration, organic matter, such as humic-like substances, can cause irreversible fouling. Therefore, this study evaluates the activity of a photocatalytic layer composed of Ce-doped zirconia nanoparticles in improving the fouling resistance during filtration of an aqueous solution of humic acid (HA). These nanoparticles were prepared by hydrothermal and sol–gel processes and then characterized. Before the filtration experiments, the photodegradation of HA catalyzed by Ce-doped zirconia nanoparticles in dispersion was studied. It was observed that the sol–gel prepared Ce-ZrO2 exhibited higher HA removal in practically neutral pH, achieving 93% efficiency in 180 min of adsorption in the dark followed by 180 min under visible-light irradiation using light-emitting diodes (LEDs). Changes in spectral properties and in total organic carbon confirmed HA degradation and contributed to the proposal of a mechanism for HA photodegradation. Finally, in HA filtration tests, Ce-ZrO2 photocatalytic membranes were able to recover the flux in a fouled membrane using visible-light by degrading HA. The present findings point to the further development of anti-fouling membranes, in which solar light can be used to degrade fouling compounds and possibly contaminants of emerging concern, which will have important environmental implications.

"Alternated cooling and heating" strategy enables rapid fabrication of highly-crystalline g-C3N4 nanosheets for efficient photocatalytic water purification under visible light irradiation

Highly-crystalline 2-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets with low structural imperfection usually possess high photocatalytic activity that benefits from the suppressed electron–hole recombination. However, the conventional exfoliation strategy is incapable for fast and clean preparation of such highly-quality g-C3N4 nanosheets from their bulk-type counterparts. Herein, highly-crystalline few-layer g-C3N4 nanosheets were synthesized only within 10 min by judiciously combining flash freezing and microwave-assisted thermo-exfoliation. Physicochemical characterization showed the ultrathin g-C3N4 nanosheets had high crystallinity, narrowed band gap (2.62 eV), enlarged specific surface area (88.59 m2/g) and enhanced electron transport ability. The quasi-2D few-layer g-C3N4 nanosheets were more efficient than bulk g-C3N4 in photocatalytic water purification and disinfection, as evidenced by 3-fold enhancement in humic acid photodegradation and fast water disinfection against Escherichia coli under visible-light irradiation. Such improvements were mainly attributed to the reduction of structural defects and enrichment of exposed active sites, which together led to efficient self-suppression of electron–hole recombination. These findings provide an inspiration for scale-up and clean production of highly-active 2D materials towards environmental and biological application.

Effect of silver sulfide nanoparticles on photochemical degradation of dissolved organic matter in surface water

Silver sulfide nanoparticles (Ag2SNPs) have shown photocatalytic activity, yet little is known about the effect of Ag2SNPs on the photochemical degradation of dissolved organic matter (DOM) in surface water, which seriously impairs understanding of Ag2SNPs' environmental risks. Herein, this study on the basis of electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) showed for the first time that photodegradation of natural organic matter (NOM, 2R101 N) could be accelerated by both bared and polyvinylpyrrolidone (PVP)-coated Ag2SNPs; the NOM with Ag2SNPs (e.g., 500 μg/L) exposed to light irradiation for 96 h showed molecular formulas with lower O/C ratios as compared to the NOM alone. Also, added number of points (ranging from 1 to 2 carboxyl groups) having the same Kendrick mass defect (KMD) (COO) values and higher intensity in smaller Kendrick mass (KM) (COO) values were observed in NOM with Ag2SNPs compared to NOM alone. However, negligible effects of Ag2SNPs on photodegradation of humic acid (HA, 2S101H) were observed, even when the concentration of Ag2SNPs was as high as 5 mg/L. Besides molecular characteristics, a great reduction in organic carbon content of NOM within 96 h was only observed in the presence of Ag2SNPs under light condition. More importantly, the enhanced photodegradation of DOM by Ag2SNPs even at a concentration of 100 μg/L was also validated in surface water. These findings suggest that Ag2SNPs have the potential to accelerate the photochemical degradation of DOM in surface water.

Photodegradation of Humic Acid and its Effect on the Property of Copper Binding

Humic acid plays an important role in regualting the physical, chemical and biological properties in aquatic systems. In this paper, photochemical degradation of humic acid and its effect on the copper binding coefficient were studied. Results showed that the copper binding coefficient decreased with increased irradiation time. The decrease of copper binding coefficient was significantly correlated with the humic acid structure parameters (SUVA270 and E2/E3) during the photodegradation. It suggested that photodegradation of humic acid may have effects on the bioaccumulation of copper and hence its toxicity to aquatic organisms.

Preparation of zinc titanate nanoparticles and their photocatalytic behaviors in the photodegradation of humic acid in water

A series of zinc titanate nanoparticles was successfully synthesized using a simple sol–gel technique. The composites were characterized by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) patterns, scanning electron microscope (SEM), X-ray photoelectron spectra (XPS) and UV–vis diffuse reflectance spectra (UV–vis). The photocatalytic activity of samples was investigated by degradation of humic acid (HA) in water under xenon lamp. The sample calcined at 800°C was found to exhibit much higher photocatalytic activity than the other samples. The investigation of photocatalytic mechanism indicates that the holes (h+) and OH radicals may be the major reactive species for the degradation of HA. Meanwhile, the processing parameters such as the light source and the dosage of catalysts play an important role in tuning the photocatalytic activity. The enhancement of photocatalytic activity for the zinc titanate nanoparticles calcined at 800°C may be attributed to the higher redox ability, coordination of Ti ions and smaller particle size.

Rapid atmospheric plasma spray coating preparation and photocatalytic activity of macroporous titania nanocrystalline membranes

Macroporous TiO 2 nanocrystalline (NC) membranes with average pore size of 0.35 μm were successfully fabricated by coating on an alumina support via a rapid atmospheric plasma spraying (APS) approach. The as-prepared TiO 2 and P25 membranes were first tested for photocatalytic activity using Reactive Black-5 (RB5) dye in a batch reactor with UV light irradiation, respectively. RB5 dyes were completely decomposed with an irradiation time of 70 min, and the rate constants for the photocatalytic reactions using TiO 2 and P25 membranes were determined to be approximately 0.076 and 0.071 min −1, respectively. The photocatalytic activity of the as-prepared TiO 2 NC membranes was slightly better than P25 membranes, indicating the APS-fabricated TiO 2 NC membranes were with a high photocatalytic activity. The TiO 2 membranes were further used for the photodegradation of dextran and humic acid (HA), and the permeate fluxes of dextran and HA increased when the membranes were exposed to UV light irradiation. The dominant filtration resistances of the dextran and HA solutions were pore and cake resistances, respectively, which were reduced by a photocatalytic TiO 2 NC membrane under UV light illumination. The removal percentages of HA at an initial concentration of 2 ppm were 58% and 90% in the dark and under UV light irradiation, respectively. The increase in the HA removal resulted from the photodegradation of HA by the photocatalytic TiO 2 NC membrane. In this work, a rapid process of APS coating was first used for the preparation of macroporous TiO 2 NC membranes with high photocatalytic activities, which can be applied for water treatment, for example, in the photodegradation of bio-organisms and protein under UV light irradiation.

Photocatalytic Activity of Heterostructures Based on ZnO and N-Doped ZnO

Different composite films prepared by coupling ZnO and nitrogen-doped ZnO (N-ZnO) were used to photodegrade humic acids (HA). The catalysts exhibit an activity in the order of glass/ZnO/N-ZnO > glass/N-ZnO >glass/ZnO > glass/N-ZnO/ZnO when light is irradiated from the film to glass substrate. However, glass/ZnO/N-ZnO exhibits a lower activity than glass/N-ZnO/ZnO when light is illuminated from glass to film. Moreover, glass/ZnO/N-ZnO shows a lower activity when light is irradiated from glass to film than that irradiated in the opposite direction. These results suggest that it is not always the case that the presence of a heterojunction at interface of two semiconductors can definitely result in improving the photoactivity of the heterostructure although it can suppress the recombination of photogenerated charge carriers. They also indicate that photodegradation of HA is mainly via the oxidization by HO• (rather than directly by O(2)(-) and h(+)), which is produced mainly by the reactions with h(+). This implies the importance of fabrication a right heterojunction at the interface between the composite materials when they are used for photocatalysis. We envision that this work will help to develop new photocatalysts, as well as to understand better the photocatalytic mechanism.

Photocatalytic performance of TiO 2 films produced with combination of oxygen-plasma and rapid thermal annealing

In this work, a combination of oxygen plasma and rapid thermal annealing was suggested in order to oxidize the surface of titanium into TiO 2. A plasma was formed by employing pure oxygen at 150 W, 300 W, and 400 W under a pressure of 7.5 to 8.5 Pa for 5 to 10 min. The TiO 2 was then subjected to rapid thermal annealing (RTA) at a temperature of 400 to 500 °C for 1 min. From the attained results, an RF power of 300 W for 5 min was observed to be sufficient to produce an optimal photocatalytic TiO 2 film. Optimal conditions were confirmed by additional experiments involving humic acid (HA) degradation of the TiO 2 films. When compared to a traditional TiO 2 film, a TiO 2 film prepared with an oxygen-plasma treatment and RTA system exhibited improved photocatalytic capability for HA photodegradation in an aqueous solution. Therefore, this process proposed in this work can be an excellent alternative to the traditional method for fabricating photocatalytic TiO 2 films.

Preparation and Photodegradation of Humic Acid by a Y<sup>3+</sup>-Doped ZnO/TiO<sub>2</sub> Composite

Aim to remove soluble humic acid (HA) in super-critical boiler make-up water, Y3+-doped ZnO/TiO2 composites were prepared using a solid-phase synthesis method, Their properties were characterized by x-ray diffraction, transmission electron microscopy, and UV-visible diffuse reflection spectroscopy (DRS); their visible light photoactivities were evaluated by the photodegradation of humic acid in an aqueous solution under sunlight irradiation.. The experiment results showed that Y3+-doped samples had a higher absorbance than pure TiO2, and a red shift appeared in the DRS spectrum; The Y3+-doped ZnO/TiO2 multiplex nanocomposite can expand the wavelength range for light absorption and increase the sunlight utilization efficiency. Samples with 3% Y3+ and 27% ZnO have the highest photoactivities.

Photodegradation of humic acid using spherical activated carbon contained Zn in a fluidized bed system

In this study, a strong acid ion-exchange resin, as the starting material of spherical activated carbon contained Zn (Zn-SPAC), was treated by 0.1 N zinc solution. Ion-exchange treatment was performed from one to three times for controlling the zinc content. The ion-exchanged resins were activated under N2/H2O vapor atmosphere at 900°C for 0.5 h, followed by carbonization treatment at 700°C under N2 atmosphere. The Zn-SPAC samples were measured for their physicochemical characteristics, such as X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) images, electron probe micro analyzer (EPMA) images, energy dispersive X-ray spectroscopy (EDXS), Brunauer–Emmett–Teller (BET) specific surface area, strength, and zinc content. Also, the samples were used in order to measure photochemical activities, such as the removal efficiency of humic acid (HA) in a fluidized batch reactor. The XRD patterns appeared as the ZnS type. The Zn-SPAC had a large BET specific surface area and their shape was spherical, with a diameter of about 350–400 μm. When the Zn-SPAC was dosed in a fluidized bed reactor with UV light, the HA removal efficiency increased by up to 60%. On the other hand, the HA removal efficiency by only UV-C (λ max = 254 nm) irradiation was very low, about 15%. Therefore, we infer that Zn-SPAC has good photochemical activity and presented the possibility of being a useful photocatalyst for water purification.

Inactivation of Bacteria E. coli and photodegradation of humic acids using natural sunlight

In this work, the disinfection of bacteria Escherichia coli and degradation of humic acids, using sunlight, sunlight+TiO2 (Degussa P25) in suspension or TiO2 supported on Ahlstrom paper (NW10) fixed around concentric tubes inside the photoreactor, were investigated in a pilot plant. The inactivation of bacteria E. coli proved to be more efficient (only 1kJUV/L for 5-log decrease in concentration) when using sunlight and TiO2 in suspension. However, true disinfection was not achieved under the conditions reported in this work. A first-order model was able to fit the photocatalytic deactivation of E. coli ([TiO2]=50mg/L) with an inactivation rate constant of 8.21L/kJ. A Langmuir–Hinshelwood-like model was successfully applied for modelling photolysis and supported-TiO2 photocatalysis of bacteria E. coli, considering an initial latency period, a classical log-linear behaviour and a tail region. The effect of the flow rate between 5 and 15L/min was negligible in the inactivation of E. coli in the presence of sunlight and supported TiO2. The inactivation rate constant increased with the initial concentration of E. coli. Almost no bacterial regrowth was observed in dark conditions during 24h after illumination of E. coli suspension until complete deactivation. The humic acids (HA) degradation was also investigated by solar photocatalysis with suspended and supported TiO2 and exposure to sunlight-only, in a CPC photoreactor. Supported-TiO2 photocatalysis of HA originated 70% concentration reduction after QUV≈14kJ/L, whereas only 20% reduction was obtained by photolysis and slurry photocatalysis. First-order kinetic constants of 0.088 and 0.010L/kJ were obtained, respectively, for suspended and supported TiO2.

Synthesis of TiO 2 nanoparticles using amphiphilic POEM- b-PS- b-POEM triblock copolymer template film

A novel ABA-type triblock copolymer, i.e. poly(oxyethylene methacrylate)- b-polystyrene- b-poly(oxyethylene methacrylate) (POEM- b-PS- b-POEM) was synthesized via atom transfer radical polymerization (ATRP). This amphiphilic triblock copolymer was used to template the growth of TiO 2 from a titanium isopropoxide through sol–gel process in the solid state film. The hydrophilic titania precursor was selectively incorporated into hydrophilic POEM domains and formed TiO 2 nanoparticle arrays, mostly due to microphase separation between the PS domains and the POEM/TiO 2 domains. High-density arrays of TiO 2 nanoparticles with 30–40 nm size after calcinations at 550 °C were confirmed by X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). The resultant TiO 2 nanoparticles showed high photocatalytic activity on the photodegradation of humic acid.

Grafted multifunctional titanium dioxide nanotube membrane: Separation and photodegradation of aquatic pollutant

Titanium dioxide (TiO2) nanotube membrane has been fabricated by an energy efficient and environmentally friendly method, grafting anatase TiO2 nanotubes in the channels of alumina microfiltration (MF) membrane using TiF4 solution through liquid-phase deposition. The inner diameters of the TiO2 nanotubes are controllable from 5 to 100nm by varying the grafting time. The TiO2 nanotube membrane exhibited good photocatalytic activity on photodegradation of HA (humic acid) in batch tests. The satisfying permeability of the TiO2 nanotube membrane was demonstrated by filtration of distilled water and HA. The experiment results of continuous filtration under UV irradiation showed that not only HA was rejected and photodegraded by the TiO2 nanotube membrane, but also the membrane fouling was alleviated dramatically.

Humic acid degradation in aqueous solution by the photo-Fenton process

The photodegradation of humic acid (HA) was carried out in the presence of the Fenton reagent. The absorbance decrease of HA was strongly influenced by the pH, and initial concentrations of H2O2 and Fe(II). An initial absorbances of HA (10 mg L −1 ) in 254 and 400 nm were completely disappeared after 8 h under the optimum conditions. The decrease of TOC as a result of mineralization of HA was observed during the photoFenton process. The degree of HA mineralization was about 80% under UV irradiation after 15 h. The molecular weight distribution changes of HA were evaluated by high performance size exclusion chromatography (HPSEC). The large molecular weight component in HA appears to be easily degraded by the photo-Fenton process than the smaller components. Furthermore, the photo-Fenton process was successfully applied to the degradation of HA in sea sediment of Ago Bay, Mie Prefecture, Japan. Based on these results, the photo-Fenton reaction could be useful technology for the treatment of environmental sample contaminated by HA. © 2007 Elsevier B.V. All rights reserved.

Adsorption and Photodegradation of Humic Acids by Nano-Structured TiO2 for Water Treatment

AbstractRemoval of natural organic matter (NOM) is always a concern in water treatment, particularly the formation of chlorinated organic compounds such as trihalomethane (THM) - toxic by-products resulting from the chlorination and disinfection of residual organic compound. TiO

Aquatic ecosystems: interactivity of dissolved organic matter

Previous articleNext article No AccessBook ReviewsAquatic ecosystems: interactivity of dissolved organic matterDonna R. KashianDonna R. KashianDepartment of Fisheries and Wildlife Biology, Colorado State University, Fort Collins, Colorado Search for more articles by this author Department of Fisheries and Wildlife Biology, Colorado State University, Fort Collins, ColoradoPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 23, Number 3September 2004 Article DOIhttps://doi.org/10.1899/0887-3593(2004)023<0662:AEIODO>2.0.CO;2 Views: 27Total views on this site Citations: 8Citations are reported from Crossref Journal History This article was published in the Journal of the North American Benthological Society (1986-2011), which is continued by Freshwater Science (2012-present). © 2004 by The North American Benthological SocietyPDF download Crossref reports the following articles citing this article:Audrey R. Douglas, Dorina Murgulet, Megan Greige, Kousik Das, J. David Felix, Hussain A. Abdulla Organic matter composition and inorganic nitrogen response to Hurricane Harvey’s negative storm surge in Corpus Christi Bay, Texas, Frontiers in Marine Science 9 (Sep 2022).https://doi.org/10.3389/fmars.2022.961206Yuji Takaki, Keisuke Hattori, Youhei Yamashita Factors Controlling the Spatial Distribution of Dissolved Organic Matter With Changes in the C/N Ratio From the Upper to Lower Reaches of the Ishikari River, Japan, Frontiers in Earth Science 10 (Mar 2022).https://doi.org/10.3389/feart.2022.826907An Shilin, Luo Chunyan, Chen Yu, Du Yingxun, Photodegradation of humic acid from the surrounding soils of a sub-alpine Lake Tiancai, Journal of Lake Sciences 34, no.22 (Jan 2022): 553–568.https://doi.org/10.18307/2022.0216Kai Wang, Yu Pang, Yunyun Li, Chen He, Quan Shi, Yuntao Wang, Ding He Characterizing Dissolved Organic Matter Across a Riparian Soil–Water Interface: Preliminary Insights from a Molecular Level Perspective, ACS Earth and Space Chemistry 5, no.55 (Apr 2021): 1102–1113.https://doi.org/10.1021/acsearthspacechem.1c00029Tingwan Zhang, Jin-Fen Pan, Dana E. Hunt, Min Chen, Bo Wang Organic matter modifies biochemical but not most behavioral responses of the clam Ruditapes philippinarum to nanosilver exposure, Marine Environmental Research 133 (Feb 2018): 105–113.https://doi.org/10.1016/j.marenvres.2017.10.016E. S. Bernhardt, W. H. McDowell Twenty years apart: Comparisons of DOM uptake during leaf leachate releases to Hubbard Brook Valley streams in 1979 versus 2000, Journal of Geophysical Research 113, no.G3G3 (Sep 2008).https://doi.org/10.1029/2007JG000618J. O. Sickman, M. J. Zanoli, H. L. Mann Effects of Urbanization on Organic Carbon Loads in the Sacramento River, California, Water Resources Research 43, no.1111 (Nov 2007).https://doi.org/10.1029/2007WR005954John A. Harrison, Nina Caraco, Sybil P. Seitzinger Global patterns and sources of dissolved organic matter export to the coastal zone: Results from a spatially explicit, global model, Global Biogeochemical Cycles 19, no.44 (Nov 2005): n/a–n/a.https://doi.org/10.1029/2005GB002480

Solar photocatalytic degradation of humic acids as a model of organic compounds of landfill leachate in pilot-plant experiments: influence of inorganic salts

Humic acids (HA) are known to be present at a high concentration in leachates from “mature” and “old” landfills. In this work, the photocatalytic degradation of Aldrich-Sigma HA as a model of refractory organic of stabilised leachate was studied. The experiments were carried out in HA aqueous suspension of TiO2 (P-25) in CPC reactor at pilot-plant scale in the Plataforma Solar de Almeria (Spain) under solar irradiation and natural pH. The adequate quantity of catalyst for this process was found to be 0.7gl−1. The effect of inorganic ions, commonly present in real leachate such as HCO3−, SO42−, Cl− on photocatalytic degradation of HA was also studied. The ions examined, even in higher concentration for Cl− (4.5g/l) and SO42− (7.75g/l) were found to not affect the photocatalytic process and the similar efficiency of HA removal was ensured. However, the presence of hydrogen carbonate into solution matrix inhibited strongly the photocatalytic reaction. The catalytic oxidation of HA, in particular in the mixture of anions, did not agree with Langumir–Hinshelwood kinetics and the evaluation of results was expressed only as an effect of HA removal versus accumulated energy (QUV, kJl−1) by photoreactor. Moreover, the effect inorganic matrix on initial adsorption of HA has been discussed on the basis of the results obtained in laboratory batch test. Additionally, the biodegradability evolution during photodegradation of HA was evaluated in terms of biological oxygen demand (BOD5) as well as by oxygen uptake rate.