Chemical Oxygen Demand Analysis Research Articles

Assessing the Washing Fastness and Environmental Impact of Various Reduction Clearing Processes on High-Performance Polyetherimide (PEI) Fabrics

AbstractPEI fibers are considered a high-performance type of fiber, known for their exceptional heat resistance and mechanical strength. These fibers, made of polyetherimide (PEI) polymer, have a completely amorphous structure, and can be dyed with disperse dyes, similar to how polyester fibers are dyed. This study focused on the reduction clearing process after dyeing PEI fibers with disperse dyes and examined various clearing agents used in both alkaline and acidic conditions, assessing how different concentrations, temperatures, and durations of reduction clearing processes affected the PEI samples. The main goal was to find the best reduction clearing parameters for disperse-dyed PEI samples, taking into account environmental impact, fabric durability, and color fastness. Analytical techniques like chemical oxygen demand (COD), biological oxygen demand (BOD5), total organic carbon (TOC), and carbon footprint analysis were used for evaluation. The study revealed that most disperse-dyed PEI fibers require a reduction clearing process, with few exceptions. It is important to note that clearing with sulfuric acid-based agents or in acidic conditions may slightly reduce the fiber’s strength. On the other hand, the study identified that utilizing a solution containing 2 g/l sodium dithionite and 4 g/l NaOH for 30 min at 70 °C resulted in the least strength loss. Similarly, when considering the environmental impact, this same reduction clearing process was found to have the least detrimental effects based on COD, BOD5, TOC, and carbon footprint analyses. The data collection process was thoroughly documented throughout the study.

Chemical oxygen demand and biochemical oxygen demand analysis of discharge waters from laundry industry: monitoring, temporal variability, and biodegradability

In Europe, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) are used as organic indicators for the analytical characterization of laundry water. However, the values of these indicators are derived from one-off analytical measurements at a defined frequency. In addition, there are few data on the temporal variability of COD and BOD5 parameters and on water biodegradability beyond 5 days. In this work, samples of physicochemical treated wastewater were collected for 1 year and their content in COD and BOD5 measured, with BOD monitored over 35 days. The results showed that, for the 24 samples studied, the average and standard deviation values were 835 ± 176 mg/L for COD and 445 ± 114 mg/L for BOD5, indicating a biodegradability index of 2.0 ± 0.4. The interpretation of the data also indicated that the concentrations were close to emission limit value, particularly for BOD5. BOD21 values were particularly high compared to the initial COD, indicating the biodegradability of water. Laundry effluents were also rich in substances very quickly biodegradable, which has been demonstrated by the values of the ratio between BOD7 and BOD5. However, a significant proportion of surfactants is not degraded, as shown by measurements of total organic carbon and anionic surfactant analysis. The results of this study could help the industrial partner involved in our project to guide its choice of the complementary method to better treat wastewater and to reduce its organic load.

Determination of seawater COD spectra using double-loop contraction and sorted frog optimization.

This study develops a novel double-loop contraction and C value sorting selection-based shrinkage frog-leaping algorithm (double-contractive cognitive random field [DC-CRF]) to mitigate the interference of complex salts and ions in seawater on the ultraviolet-visible (UV-Vis) absorbance spectra for chemical oxygen demand (COD) quantification. The key innovations of DC-CRF are introducing variable importance evaluation via C value to guide wavelength selection and accelerate convergence; a double-loop structure integrating random frog (RF) leaping and contraction attenuation to dynamically balance convergence speed and efficiency. Utilizing seawater samples from Jiaozhou Bay, DC-CRF-partial least squares regression (PLSR) reduced the input variables by 97.5% after 1,600 iterations relative to full-spectrum PLSR, RF-PLSR, and CRF-PLSR. It achieved a test R2 of 0.943 and root mean square error of 1.603, markedly improving prediction accuracy and efficiency. This work demonstrates the efficacy of DC-CRF-PLSR in enhancing UV-Vis spectroscopy for rapid COD analysis in intricate seawater matrices, providing an efficient solution for optimizing seawater spectra.

Polyacrylamide degradation in oil field wastewater by UV/H2O2 and UV/PDS: Rapid experimental measurement and model simulation

Ultraviolet-based advanced oxidation processes (UV-AOPs) are effective for degrading refractory pollutants in wastewaters. However, performing rapid efficiency evaluations represents a significant challenge for process selection and optimization in practical application. This study investigated polyacrylamide (PAM) degradation by UV/hydrogen peroxide (H2O2) and UV/potassium peroxydisulfate (PDS) in pure water and practical oil field wastewater. Based on a previously developed mini-fluidic photoreaction system that is easy to operate and requires low sample volumes, an experimental setup for rapid evaluation of UV-AOP efficiency was constructed that enabled on-line analyses of viscosity, UV absorbance, and pH via specially fabricated flow cell devices together with off-line analyses of PAM, chemical oxygen demand (COD), and acrylamide (AM). The PAM degradation rate constants (k′PAM) in practical oil field wastewater by UV/H2O2 and UV/PDS were 2.4 and 2.1 m2 einstein−1, respectively, which were much higher than those by sole UV process (0.8 m2 einstein−1). Combing with the analyses of viscosity, UV absorbance (220 nm), pH, COD, and AM concentration, the UV/H2O2 and UV/PDS demonstrated the effectiveness in PAM degradation in oil field wastewater. Additionally, the scavenging capacities of HO• and SO4•− of practical oil field wastewater were determined, and the k′PAM values were predicted by model simulation and verified experimentally. This study provides rapid evaluation methods for UV-AOP efficiencies, which is helpful for selecting and optimizing UV-AOPs for industrial wastewater treatments.

Photoelectrocatalytic chemical oxygen demand analysis using a TiO2 nanotube array photoanode

The chemical oxygen demand (COD) is a widely used parameter to evaluate the quality of water for industrial applications. Currently, the standardized method for COD analysis employs expensive and harmful reagents that require a special treatment for disposal upon use. The photoelectrocatalytic COD detection, based on the photocatalytic activity of a reduced TiO2 nanotube array photoanode (Ti|NT-TiO2) under supply of a low bias potential, represents a fast, cheap and eco-friendly alternative to the standard COD method (CODSTD). Here, Ti|NT-TiO2 was synthesized by the anodization method followed by heat treatment and electrochemical reduction. Potassium hydrogen phthalate, glucose and acetic acid were used as model organic compounds. The photoelectrocatalytic detection of COD (CODPEC) is based on the photoelectrocatalytic oxidation of target compounds on the surface of the reduced Ti|NT-TiO2 under UV illumination. Photocurrent transients were recorded using chronocoulometry, and the net charge (Δq) was plotted as a function of the theoretical COD (CODTH). A linear relationship was found between these two parameters regardless of the model compound. That relationship was used to determine the CODPEC for acetylsalicylic acid and Terasil Blue dye solutions at concentrations within the range of 0–15 mg L−1. A good agreement between CODPEC and CODSTD was achieved. The limit of detection of the method was 3.6 mg L−1 COD, with the linear range established from 0 to 50 mg L−1.

Dissolved organic material changes during combined treatment of a mixture of landfill leachate and anaerobic digestate using deammonification and chemical coagulation.

The current study investigates the combined treatment of wastewater of anaerobic digestate and landfill leachate, using deammonification and coagulation/flocculation processes. The deammonification section studies the performance of a full-scale deammonification plant in nitrogen and chemical oxygen demand (COD) removal, monitored over 2 years. For further COD reduction from the deammonification effluent (DE) to meet the environmental regulatory standards, coagulation/flocculation using three different Al-based coagulants was used to treat the DE. Results revealed that the deammonification plant showed 80% average ammonium removal from the mixed feed over the study period. Additionally, 30% of the feed COD was removed in the deammonification plant. COD analysis after treatment using coagulants revealed that the polyaluminum chloride modified with Fe had the best performance in reducing COD to meet the environmental standards. Excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) of the dissolved organic material (DOM) samples indicated that fluorescents were the compounds mostly affected by the coagulant types. DOM analysis using 2D correlation Fourier-transform infrared spectroscopy revealed that the applied coagulants showed minor differences in removing different functional groups, despite having different COD reduction performance. Wastewater elemental analysis indicated elevated metal concentrations in low pH conditions (<6) due to re-stabilization of the flocs using coagulants.

Reduction of fines in recycled paper white water via cellulase enzymes

Due to the high wastepaper recyclability and water-loop system closure, packaging paper mills struggle with increased fines, causing runnability issues. Cellulase enzymes are a preferred treatment choice for the improvement of the pulp refining in stock preparation area but are not widely used or easy to introduce in the production process. Different cellulase enzymes were tested, and those with the highest activity were introduced to the white-water (WW) samples with the aim to reduce fines content as potentially new enzyme applications on the paper machine. The first portion of the study involved the development of an experiment model to find and confirm the optimal enzyme process parameters (40 °C, pH 5.7, reaction time 3 h, and 0.18% v/v enzyme addition) for laboratory made white-water. The second portion of the study included turbidity, colloidal charge, flow cytometry (FCM), and chemical oxygen demand (COD) analysis on industrial and laboratory made white-water samples at optimized process parameters. Obtained results corresponded to reduced fines content in white-water samples, which justified commercial usage of cellulase enzymes on recycled paper machine short loop and potentially increased machine runnability without negative influence on wastewater treatment plant.

Sulphate-based electrochemical processes as an alternative for the remediation of a beauty salon effluent‡

Beauty salons (BS) are places that deal with a wide range of cosmetics with potentially hazardous chemicals, and their effluent should be properly treated before going to the sewage system, once it represents characteristics of industrial wastewater. This work provides an extensive characterization of a BS effluent and its respective electrochemical treatment by comparing NaCl, Na2SO4, and Na2S2O8 as supporting electrolytes with a boron-doped diamond (BDD) as anode, applying 10 or 30 mA cm−2 of current density (j). The inclusion of UVC irradiation was also performed but the improvements achieved in removing the organic matter were null or lower. The analysis of chemical oxygen demand (COD) removal, energy consumption, and total current efficiency (TCE) was required to prove the efficacy of the processes and the comparative study of the performance of different technologies. Precipitate analysis was also done due to the high turbidity of the raw effluent and the appearance of a precipitate before and during the electrolysis, mainly with Na2S2O8. The precipitate confirmed the presence of silicates and small amounts of heavy metals. The results clearly showed that 6 h of treatment with Na2SO4 achieved 58% of COD removal with an energy consumption of about 0.52 kWh m−3, being the best electrolyte option for treating BS effluent by applying 10 mA cm−2. Under these experimental conditions, the final wastewater can be directly discharged into the sewage system with a lower amount of visible precipitate, and with 73% less turbidity. The treatment here proposed can be used as an alternative to decision-makers and governments once it can be a step further in the implementation of better and advanced politics of water sanitation.

Green synthesis of recyclable reduced graphene oxide-gold nanocatalyst using Alstonia scholaris: Applications in waste water purification and microbial field

The green synthetic approaches are the alternative methods for the preparation of various types of nanoparticles to keep sustainable evolution. A novel green synthesis of gold- reduced graphene oxide nanocomposites was conducted through simple heating method using Alstonia scholaris (A. scholaris) bark extract. There are several techniques that confirm the formation of the nanocomposites for synthesis of gold nanoparticles on reduced graphene oxide (RGO), such as X-ray diffraction (XRD), UV–visible spectroscopy (UV–vis) and Fourier transformed infrared spectroscopy (FT-IR). The size distributions of the gold nanoparticles (Au NPs) grown on RGO surface was measured using two different methods: particle distribution study and transmission electron microscopy (TEM) image. These two methods provided similar size distribution which is around 5–8 nm. Subsequently, the catalytic performance was evaluated by 4-nitro aniline (4-NA). The photocatalytic activities were investigated using different organic hazardous dyes, such as methylene blue (MB), methyl orange (MO) and the change of photocatalytic behaviour was shown by varying the catalyst amount and pH. The chemical oxygen demand (COD) analyses for complete removal of organic dye were carried out using the two nanocomposite samples. To perceive the effect on different bacterial strains, antibacterial and antiprotozoal studies have been carried out with this nanocomposite.

Comparison of COD Determination Methods FAS Titrimetric with UV-Vis Spectrophotometry

Liquid waste is one of the factors causing contamination of the aquatic environment. One of the chemical parameters of water quality namely Chemical Oxygen Demand (COD). This research was conducted at three different concentration levels, namely low, medium, and high, with samples of river water, domestic wastewater, and sago liquid waste. The method used is UV-Vis spectrophotometry (SNI 6989.2: 2019) and FAS titrimetry (APHA, 2017 methods 5220 D); for the UV-Vis spectrophotometry method in the range 90 mg/L, the wavelength was measured at 420 nm, while for high levels in the range 100 mg/L x 900 mg/L, it was measured at 600 nm. The quality control parameters used are accuracy and precision parameters. The purpose of this study was to compare the COD determination between UV-vis spectrophotometry and FAS titrimetry and to determine the validity and correlation of the two methods—a comparison of the results of the two methods used in the F test. The results showed that the COD values from UV visible spectrophotometry and FAS titrimetry yielded good precision and accuracy values and met the acceptable limits, namely %RSD 10% and 90% accuracy %R 110%. However, the results of the COD analysis using the UV-Vis spectrophotometry method were lower by 0.8556 than the results of the COD analysis using the FAS titration method, with a correlation coefficient r2 = 0.982. The average concentration of UV-Vis spectrophotometry in samples of sago wastewater was 572.141 mg/L, domestic wastewater was 113.525 mg/L, and river water was 42.98 mg/L. The average COD level of the titrimetric method in sago wastewater was 641.888 mg/L, domestic wastewater was 219.251 mg/L, and river water was 58.016 mg/L. The results of the F test for these two methods produce an Fcount Ftable. The null hypothesis (Ho) is rejected, meaning there is a significant difference between the two methods.

Polypyrrole/ silver/graphene ternary nanocomposite synthesis and study on photocatalytic property in degrading Congo red dye under visible light

In this report, a simple chemical synthesis of polypyrrole/silver/graphene (Ppy/Ag/Gr) ternary nanocomposites with varying concentrations of graphene are described. The XRD spectra of the samples polypyrrole/silver (Ppy/Ag) and Ppy/Ag/Gr show all the peaks of the face-centered cubic structure of silver. A broad peak between 10° and 20° and a peak at 26.7° corresponds to Ppy and graphene respectively. Using FTIR, and UV–Vis. spectroscopies the interaction between polypyrrole, silver, and graphene were studied. In our work, we explored the photocatalytic property of the synthesised samples by using them to degrade the aqueous solution of a cancer-causing dye, Congo red. The percentage degradation of Congo red dye using the sample Ppy/Ag/Gr (0.5 wt.%) is obtained as 96% and the reaction rate calculated is 0.162/min., greater than that of Ppy/Ag and Ppy/Gr binary composites. Thus, the addition of the optimum concentration of graphene into Ppy/Ag enhanced its photocatalytic property. The BET analysis shows an increased surface area for the sample Ppy/Ag/Gr (0.5 wt.%) and the reason for the enhancement of photocatalysis with this sample is confirmed since it is a surface-dependent property. The biodegradability of the dye solution was investigated by Chemical Oxygen Demand (COD) analysis and the COD value was reduced from 432 mg/L to 216 mg/L after 20 min of irradiation of light.

CONTRIBUTORY IMPACT OF SEWAGE ON POLLUTED OGUN AND LAGOS FISHING WATERS: INFLUENCE ON ANTIOXIDANT PROFILE AND PROXIMATE COMPOSITION OF SILVER CATFISH (Chrysichthys nigrodigitatus)

Water pollution, a recurring phenomenon in fishing waters of industrial cities in Nigeria, inadvertently constitute hazards to the host biotic communities and the ecosystem. To continuously delineate the impacts of pollution via sewage outlets on aquatic life, this rainy season study investigated Chrysichthys nigrodigitatus, an aquatic food from Ogun River and Epe Lagoon, Nigeria, both of which are locally channeled for sewage release. Sixty (60) samples of C. nigrodigitatus were collected from six sites each representing a group (n=10), with mean weight and length of 762.20 ± 11.05 g and 42.21 ± 0.30 cm respectively. Ajegunle (control), Alaapa and Quarry (test sites) along the Ogun River course in Abeokuta; Ebute-Alashe (control), Oluwo and Marina (test sites) along the Epe Lagoon. Analysis of Biochemical Oxygen Demand and Chemical Oxygen Demand showed elevated variations at the sampled test sites than the control sites and above WHO safe limits. Significant (p &lt; 0.05) increases in concentrations of heavy metals (lead, arsenic and cadmium) in the fishing waters from the sampled test locations particularly the Quarry and Marina sites, as well as in blood samples of fish, were observed when compared with their respective controls. Antioxidants profiling showed significant increases (p &lt; 0.05) in superoxide dismutase and catalase activities in fishes from Alaapa (14- and 3- folds), Quarry (8- and 4- folds), Oluwo (9- and 3- folds) and Marina (8- and 3- folds) sites, while significant increases in glutathione-S-transferase activity were observed only in fishes from Quarry (5- fold) and Marina (4- fold) sites respectively. The glutathione concentration significantly decreased in fishes from all the test sites while malondialdehyde concentrations significantly increased in fishes from all the test sites compared with the respective controls. Proximate analysis of the fish samples showed significant increases (p &lt; 0.05) in moisture and fiber contents, but significant decrease in fat, ash and protein contents compared with the respective controls. The results of the study showed that sewage pollution of fishing waters is hazardous to aquatic life as it induces oxidative stress and significantly reduces the nutritional value of the fishes obtained from such water bodies.

Electro-oxidation of wastewater from a beauty salon: The influence of electrolyte type in the removal of organic load and energy consumption

The aim to ensure water quality and wastewater treatment is sought by the United Nations and expressly proposed in the sixth sustainable development goal (SDG6). As universally available services, beauty salons (BS) are places that deal with potentially hazardous chemicals, and their effluent should be treated before goes to the sewage system. This work presents a wide characterization of a BS effluent and its respective electrochemical treatment by using boron-doped diamond (BDD) as the anode, stainless steel as the cathode, as well as NaCl and Na2SO4 as additional supporting electrolytes. The effectiveness of the processes and the comparative study of the performance of the electrolytes were mainly performed by the analysis of chemical oxygen demand (COD) removal and energy consumption. However, other parameters were taken into consideration, such as color, conductivity/salinity, pH, and more extensive analysis regarding the cause of turbidity and the appearance of a precipitate before and during the electrolysis. NaCl proved to be more efficient than Na2SO4 to treat this BS effluent; it was not only because achieves a better COD removal (70% against 64%, with a current density of 10 mA cm−2), but also because it promoted an effluent with less turbidity and color, besides a pH closer to neutral, with no need to further correction before discharge. Regarding the electrolyte concentration, the excess of salt proved to be necessary to promote a higher removal rate in COD values with less charge and energy consumption. Thus, the concentration of 0.16 M of NaCl associated with a current density of 10 mA cm−2 was chosen as the best condition for treating this effluent. In addition, Si-based oxides were detected in the raw effluent and these were pointed out as responsible for its high turbidity. Proper discharge of it into the sewage system is reached with NaCl as the electrolyte. The treatment proposed in this work deals with SDG6 and can be used as an alternative to decision-makers and governments to help in the implementation of better politics of water sanitation.

Cost-effective smartphone-based method for low range chemical oxygen demand analysis

Aiming the decentralization of monitoring policies and to facilitate the work of researchers, mainly in developing countries, the present method deals with the explanation of a simple and rapid protocol for chemical oxygen demand (COD) analysis through the use of digital smartphone devices coupled with a camera and a free app available for Android operating system that recognizes HSV (hue, saturation, value). The calibration of the method is done based on the theoretical values of potassium hydrogen phthalate for a proper and reliable build of the calibration curve by using the smartphone-based technique and the digested samples of COD. The coefficient of determination (R2) attained a value upper than 0.99, providing a high confidence levels, and the method achieved 97% of average accuracy in samples with COD values ranging from 0 to 150 mg L−1. Finally, the procedure here presented can be a great support for scientific laboratories and monitoring policies, once it can efficiently substitute expensive spectrophotometers and can improve and ensure the sustainable management of water sanitation, which is one of the sustainable goals proposed by the United Nations.•COD measurements, based on the use of a simple smartphone with a camera, can be a promising way for environmental analysis when spectrophotometers are not available, such as decentralized approaches.•The use of smartphone protocol is a novel initiative to fulfill sustainable development goal 6 on clean water and sanitation.•The smartphone is capable to read the difference of HSV values efficiently and can substitute the use of expensive spectrophotometers.

Decentralized environmental applications of a smartphone-based method for chemical oxygen demand and color analysis

This study is focused on a proposal of a smartphone imaging-based quantification for providing a simple and rapid method for the analysis of chemical oxygen demand (COD) and color throughout the use of the HSV and/or RGB model in digital devices. For COD, calibration curves were done based on the theoretical values of potassium biphthalate for a proper comparison between the spectrophotometer and the smartphone techniques. The smartphone camera and application attain an average accuracy higher than the analysis in the spectrophotometer (98.3 and 96.2%, respectively). In the color analysis, it was demonstrated that only the UV–vis bands measurement is not feasible to perform the real abatement of the dye in the water because the limiting concentration that allows obtaining a linear relationship in this equipment related to the dye concentration is about 10 mg L−1. Above this value, the spectrophotometer can not reach the real difference of color in the solution. Meanwhile, the smartphone method by using the camera reaches linearity until 50 mg L−1. From an environmental point of view, smartphones have been used for monitoring several organic and inorganic pollutants, however, no attempts have been published related to their use to evaluate the color and COD during wastewater treatment. Therefore, this investigation also aims to assess the utilization of these methods, for the first time, when high-colored water polluted by methylene blue (MB) was electrochemically treated by using a boron-dopped diamond (BDD) as the anode, with different current densities (j = 30, 45, 60, and 90 mA cm−2). COD and color abatement results clearly showed that different organic matter/color removal efficiencies were achieved, depending on the j used. All the results are aligned with the studies already available in the literature, with the total removal of color in 120 min of electrolysis with 60 and 90 mA cm−2, and almost 80% of COD abatement with the higher j. Moreover, samples of real effluent from beauty salons were compared, with standard deviation varying from only 3 to 40 mg O2 L−1, which is acceptable for COD values close to 2000. Finally, the methods here presented can be a great benefit for public water monitoring policies, since it is cheap and has a decentralized characteristic, given that smartphones are very common and portable devices.

Application of PeCOD and dichromate methods for the analysis of chemical oxygen demand (COD) in the wastewater sample

Chemical oxygen demand (COD) is one of the critical environmental parameters in determining the organic matter in water matrices. The conventional dichromate method employs hazardous reagents and heat reflux. In order to reduce hazardous waste, several alternative methods have been proposed to replace the dichromate. The photoelectrochemical COD (PeCOD) method has become a promising one for being less time-consuming, environmentally friendly, and more reliable. To ensure the result, a comparison between PeCOD and dichromate methods should be conducted. In this study, we analyzed the technical features of the PeCOD method, especially for the accuracy in measuring certified reference material (CRM), and identify the advantages and disadvantages of this method. Afterward, we applied both PeCOD and dichromate methods to analyze tofu processing wastewater as a representative of environmental samples. The result showed that PeCOD gave a recovery of 113.1±4.8% whereas the dichromate method gave a recovery of 98.4±1.7%, which indicates that the PeCOD method had lower accuracy than the dichromate method. Meanwhile, the COD concentration of tofu processing wastewater using PeCOD and dichromate methods was 11516±669 mg/L and 9109±680 mg/L, respectively. This difference might be due to overestimation by the PeCOD method, the complex matrix of the wastewater, and chloride interference.

Mesostructured lead dioxide grown on titania nanotubes for diclofenac water removal through electrocatalytic and photoelectrocatalytic processes

Mesostructured PbO2/TiO2 materials were synthesized to perform electrocatalysis (as electrooxidation, EO) and photoelectrocatalysis for removing diclofenac (DCF), 15 ppm concentration in 0.1 M NaSO4 solutions, at different pH conditions (3.0, 6.0 and 9.0) by applying 30 mA cm−2. Titania nanotubes (TiO2NTs)-based materials were prepared to synthetize with a massive PbO2 deposit on this support to obtain TiO2NTs/PbO2 and a TiO2NTs:PbO2 material consisting in a dispersed PbO2 deposit on TiO2-NTs that allowed the formation of a heterostructured surface of combined composition (TiO2 and PbO2). Organics removal (DCF and byproducts) was monitored through UV–vis spectrophotometry and high-performance liquid chromatography (HPLC) during degradation tests. TiO2NTs/PbO2 electrode was tested in both processes, removing DCF at neutral and alkaline solution conditions in EO while an unimportant photoactivity was registered at this material. Conversely, TiO2NTs:PbO2 was used as electrocatalytic material in EO experiments, achieving more than 50% of DCF removal at pH 6.0 by applying 30 mA cm−2. Also, for first time, the synergic effect was investigated when it was exposed to UV irradiation in photoelectrocatalytic experiments, enhancing its efficacy (⁓more than 20%) to remove DCF from a solution with 15 ppm over performance removals achieved (56%) when EO was applied under similar conditions. Chemical Oxygen Demand (COD) analyses showed that significantly higher DCF degradation is reached under photoelectrocatalysis, since COD values decrease a 76% against a 42% decrease achieved with electrocatalysis. Scavenging experiments showed a significant participation on the pharmaceutical oxidation process through the generation of photoholes (h+), hydroxyl radicals and sulfate-based oxidants.

UV Induced Photocatalytic Degradation of Caffeine Using TiO2–H-Beta Zeolite Composite

An anatase phase of the TiO2-H-beta (THB) zeolite composite photocatalyst is used for the photocatalytic degradation of caffeine, a persistent organic pollutant (POP). It is synthesized by a simple two-step sol-gel method. Phase formation, morphology, bandgap, and photocatalytic properties were analyzed using powder X-ray diffraction, scanning electron microscopy, and UV-Vis diffuse reflectance spectroscopy, respectively. The THB and the anatase TiO2 samples were then tested for the photocatalytic activity of the degradation of caffeine. Photocatalytic studies reveal that the as-prepared THB composite showed excellent activity for the degradation of 10 ppm caffeine solution. The chemical oxygen demand (COD) analysis found caffeine to have degraded with an efficiency of 96%. Scavenging experiments indicated that the hydroxide radical played an important role in the degradation of caffeine. The results highlight the role of the H-beta zeolite as an effective support to TiO2 and improved the photocatalytic activity. The study demonstrates that the THB composite could be effectively applied for the photocatalytic degradation of other POPs largely present in active pharmaceutical ingredients.

Photocatalytic Degradation of Organic Dyes from Clinical Laboratory Wastewater

Clinical laboratory wastewaters are of important environmental concern due to the highly complex chemical reagents and dyes used to identify various pathologies, which are difficult to degrade by conventional treatment methods. The present research aimed to assess the effects of ilmenite use in the discoloration process of clinical laboratory wastewater. The wastewater originates from a Gram staining process used to identify pathogenic microorganisms present in biological samples. The active ingredient is crystal violet, a triphenylmethane dye derivative, highly toxic and non-biodegradable that causes a shiny purple color in the wastewater. The ilmenite was characterized by X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, energy-dispersive spectroscopy and Nitrogen adsorption isotherm, while the discoloration process of the wastewater was measured by UV–Vis spectrophotometry and pH change trough the reaction time, evaluating different ilmenite loads, particle size and stability under light sources with different energies. Chemical oxygen demand analysis confirmed that acid formation and discoloration were associated with organic substance mineralization. Type C ultraviolet light and 0.7 g/L load were identified as the best operating conditions for the discoloration process. It was possible to establish that ilmenite is stable after four uses in the discoloration process, obtaining, in all cases, discoloration percentages higher than 90% after 3 h of irradiation.

A comparative study on the mineralization of waste butyl acetate by electrochemical oxidation via persulphate/hypochlorite and silver (II) reagents using DSA® anodes: Statistical optimization by response surface methodology

AbstractMediated electrochemical oxidation of butyl acetate (BA) in wastewater was conducted by employing two different techniques based on S2O8−2/ClO− and Ag (II) reagents using commercial Dimensionally Stable Anode (DSA)®‐O2 or DSA®‐Cl2 anodes. Response surface methodology (RSM) was also engaged to investigate process parameters impacts and their interactions on BA mineralization efficiency and energy consumption. Fourier‐transform infrared spectroscopy (FT‐IR), UV–visible, and gas chromatography (GC) analyses confirmed BA mineralization and the optimum removal conditions were then attained for both systems. Chemical oxygen demand (COD) analysis showed that electro‐oxidation by mixed persulphate/hypochlorite oxidants favours the mineralization of BA (99.7%) compared to the Ag (II) technique (96.56%). The higher removal efficiency obtained by S2O8−2/ClO− was achieved in a neutral aquatic medium using DSA®‐Cl2 at a lower current density (CD), temperature, and electrolysis time (pH: 6, CD: 0.1 kA/m2, and time: 60 min) compared to those obtained by Ag (II) ions (pH: ≤3, CD: 1.69 kA/m2, and time: 130 min). The former process occurred under the charge transfer control mechanism at low CDs, whereas at an elevated CD (about 1.0 kA/m2), mass transfer was predominant due to the parasitic oxygen evolution. On the other hand, the latter process was found charge transfer‐controlled at low BA concentrations (≤200 ppm), whereas it turned out mass transfer‐controlled at higher BA concentrations. Comparing the anode type, energy consumption for BA mineralization by S2O8−2/ClO− ions using DSA®‐Cl2 at the optimum conditions was 0.009 kW · h/dm3, which was about three times lower than that of the DSA®‐O2 anode.