Decrease In Chemical Oxygen Demand Research Articles

Catalytic Degradation of Bisphenol A in Water by Non-Thermal Plasma Coupled with Persulfate

Bisphenol A (BPA) has become prevalent in the environment due to its extensive use in industrial materials, thus raising significant concerns regarding its potential toxicity and health effects. In this study, an efficient and eco-friendly non-thermal plasma (NTP) was used to catalyze persulfate (PS) for BPA decomposition, and the results showed that the integrated system could effectively degrade BPA. The best performance was attained at a PS to BPA mass ratio of 5:1, with a degradation rate of 91.3% following a 30 min treatment. The degradation rate of BPA increased with increasing input voltage and frequency; conversely, it decreased with an increase in BPA’s initial concentration. Higher BPA degradation rates could be achieved in alkaline environments. Radical quenching experiments revealed that SO4−•, OH•, O2−• and 1O2 were important active substances involved in BPA degradation. Nine intermediate products were identified by liquid chromatography–mass spectrometry (LC-MS), and four degradation pathways were deduced. Additionally, a toxicity analysis of intermediate products was performed. The significant decrease in chemical oxygen demand (COD) during the actual wastewater treatment suggested that the NTP/PS system has good applicability in actual wastewater treatment.

Phytopurifying activity of Salvia officinalis L. from Tunisia

The sage (Salvia officinalis L.) is an annual and biennial plant of Mediterranean origin from the Lamiaceae family. It's a valuable medicinal plant, which is widely used in traditional medicine in world and in Tunisia; this species is very rich in active biological compounds.The objective of this study was to determine the phyto-purifying activity of sage essential, fixed oil and ethanolic extracts in an extensive wastewater purification system of Tunisian national sanitation office. We have measured the physico-chemical parameters of wastewater treated with sage oils and extracts. Then, we have carried out a bacteriological analysis of this wastewater.Our results showed that pH values measured following treatment with sage essential oil gave a pH close to neutral. Therefore, this water can be used for irrigation. In addition, the sage leaves and stems have a considerable effect on the salinity and caused a very remarkable increase in electrical conductivity of the wastewater, the measure of elimination rate demonstrated the effectiveness of sage extracts in eliminating all the microorganisms existing in wastewater.In fact, sage essential oil has the greatest effectiveness in reducing the chemical oxygen demand of the wastewater and we have noticed that a decrease in chemical oxygen demand of microorganisms existing in the wastewater was necessarily accompanied by a decrease in biological oxygen demand. Therefore, sage leaves and stems were more effective in reducing suspended matter existing in wastewater.

Tratamiento químico de vinaza de caña de azúcar con peróxido de hidrógeno

[Introduction]: Vinasse is generated as a residue in the production of ethanol by fermentation-distillation of molasses/sugar cane juice, at a rate of 13 L/L of ethanol. It is an acid liquid, brown in color, characterized by high mineralization and Chemical Oxygen Demand (COD) values of up to 150 000 mg/L, being highly polluting. [Objective]: The objective of this research was to evaluate a vinasse treatment process with hydrogen peroxide as a source of hydroxyl radicals at laboratory scale. [Methodology]: The vinasse samples, from different distilleries in the province of Tucumán, were characterized following standardized techniques of Standard Methods. The oxidation tests were carried out with different peroxide/vinasses ratios, in a semi-batch reactor, under ambient conditions, measuring COD as an indicator parameter of the treatment. [Results]: After 5 days, an 85 % decrease in COD and an increase in the Biodegradability Index were achieved. The kinetics of the oxidative reaction was first order with respect to COD, with an apparent rate constant of 0.3694 1/day. [Conclusions]: Although the COD values allowed by local regulations (250 mg/L) were not reached, the proposed treatment is encouraging due to its simplicity, representing a potential option to the environmental challenge represented by vinaze in Latin America.

Pollutant degradation and hydrogen production of landfill leachate membrane concentrates via aqueous phase reforming

Membrane filtration is a mainstream method for landfill leachate treatment, leaving the landfill leachate membrane concentrates (LLMCs) a high-toxicity residue. Conventional LLMCs disposal technology shows specific challenges due to the low biodegradability, high inorganic salts, and high heavy metal ions content of LLMCs. Therefore, it is necessary to degrade LLMCs with a more suitable technology. In this study, a special method was proposed to convert some organic chemicals into valuable compounds by aqueous phase reforming (APR). Ni-based catalysts (Ni//La2O3, Ni/CeO2, Ni/MgO, and Ni/Al2O3) were prepared to investigate the effect of different supports on the APR of LLMCs. APR performed outstanding characteristics in the decrease of chemical oxygen demand (COD) and total organic carbon (TOC), the degradation of macromolecules, and the removal of heavy metal ions in the aqueous phase. In addition, H2 was generated which is beneficial for energy compensating during the APR process. The best-performing catalyst (Ni/Al2O3) was selected to investigate the effects of reaction temperature, reaction time, and catalyst addition on product distribution. The optimal H2 selectivity (44.71%) and H2 production (11.63 mmol/g COD) were obtained at 250 °C with 2 g Ni/Al2O3 usage for 1 h. This paper provided a new perspective on the disposal of LLMCs, which will degrade pollutants efficiently.

Effective reduction of carbon-containing pollutants in coffee cherry pulping wastewater using natural polysaccharide from Tamarindus indica L. seeds

The wastewater produced during coffee cherry pulping is known for containing harmful pollutants, particularly organic compounds containing carbon, which pose significant risks to the environment and human health. This research aimed to evaluate the effectiveness of Tamarindus indica L. seed polysaccharides in treating coffee effluent. Varying doses (ranging from 0.05 to 0.30 g) of the isolated polysaccharides were added to samples of the effluent to determine their ability to remove contaminants, especially those of organic carbon origin. Notably, a dosage of 0.10 g demonstrated optimal efficacy, resulting in a 55% decrease in total dissolved solids and an 80% decrease in chemical oxygen demand. Additionally, Fourier-transform infrared and zeta potential analysis of both the polysaccharides and the treated effluent samples revealed the presence of functional groups potentially pivotal for the pollutant removal activity of the isolated polysaccharides. This provides insights into the coagulation mechanism of Tamarindus indica L. seed polysaccharides in eliminating organic carbon-based pollutants. These findings highlight the potential of Tamarindus polysaccharides as a sustainable alternative to chemical agents for removing pollutants, thus promoting environmental sustainability and human well-being.

Hydrodynamic Cavitation – A Promising Technology for Water Treatment

In today's context, water treatment assumes paramount importance due to the scarcity of potable water and the escalating needs of the global population. Hydrodynamic Cavitation (HC) emerges as a promising application in wastewater treatment, particularly when integrated with Advanced Oxidation Processes (AOPs). The study begins with a critical examination of the literature on combined approaches involving hydrodynamic cavitation, followed by experimental findings. The primary objective was to mitigate the chemical oxygen demand (COD) of the sample through HC in conjunction with hydrogen peroxide and Fenton reagent. Subsequently, each run was executed, and the output value obtained from HC was determined. Throughout the research, samples of river water were procured from the Mula-Mutha River in Pune. HC treatment reduced the COD of river water by approximately 60.83 % at 3 pH. Notably, the highest degradation was observed at 9 pH with the use of Sodium persulphate, with the optimal concentration estimated to be 600 ppm. Moreover, a COD reduction exceeding 89 % with a dosage of 15 mM H2O2. Treatment with Fenton reagent for 60 min demonstrated a remarkable COD decrease of up to 93 %, with an optimal H2O2 to FeSO4 molar ratio of 10:1 and at 3 pH. The Fenton procedure alone or in combination with H2O2 and HC proved to be the most efficient for river water characterized by extremely high COD levels, yielding the greatest reduction during experimental trials. The kinetics of HC degradation conformed to a first-order rate law, with the value of a rate constant (K = 7.21 × 10-4 s−1).

Wastewater treatment from a science faculty during the COVID-19 pandemic by using ammonium-oxidising and heterotrophic bacteria

During and after the pandemic caused by the SARS-CoV-2 virus, the use of personal care products and disinfectants increased in universities worldwide. Among these, quaternary ammonium-based products stand out; these compounds and their intermediates caused substantial changes in the chemical composition of the wastewater produced by these institutions. For this reason, improvements and environmentally sustainable biological alternatives were introduced in the existing treatment systems so that these institutions could continue their research and teaching activities. For this reason, the objective of this study was to develop an improved culture medium to cultivate ammonium oxidising bacteria (AOB) to increase the biomass and use them in the treatment of wastewater produced in a faculty of sciences in Bogotá, D.C., Colombia. A Plackett Burman Experimental Design (PBED) and growth curves served for oligotrophic culture medium, and production conditions improved for the AOB. Finally, these bacteria were used with total heterotrophic bacteria (THB) for wastewater treatment in a pilot plant. Modification of base ammonium broth and culture conditions (6607 mg L−1 of (NH4)2SO4, 84 mg L−1 CaCO3, 40 mg L−1 MgSO4·7H2O, 40 mg L−1 CaCl2·2H2O and 200 mg L−1 KH2PO4, 10% (w/v) inoculum, no copper addition, pH 7.0 ± 0.2, 200 r.p.m., 30 days) favoured the growth of Nitrosomonas europea, Nitrosococcus oceani, and Nitrosospira multiformis with values of 8.23 ± 1.9, 7.56 ± 0.7 and 4.2 ± 0.4 Log10 CFU mL−1, respectively. NO2− production was 0.396 ± 0.0264, 0.247 ± 0.013 and 0.185 ± 0.003 mg L−1 for Nitrosomonas europea, Nitrosococcus oceani and Nitrosospira multiformis. After the 5-day wastewater treatment (WW) by co-inoculating the three studied bacteria in the wastewater (with their self-microorganisms), the concentrations of AOB and THB were 5.92 and 9.3 Log10 CFU mL−1, respectively. These values were related to the oxidative decrease of Chemical Oxygen Demand (COD), (39.5 mg L−1), Ammonium ion (NH4+), (6.5 mg L−1) Nitrite (NO2−), (2.0 mg L−1) and Nitrate (NO3−), (1.5 mg L−1), respectively in the five days of treatment. It was concluded, with the improvement of a culture medium and production conditions for three AOB through biotechnological strategies at the laboratory scale, being a promising alternative to bio-augment of the biomass of the studied bacteria under controlled conditions that allow the aerobic removal of COD and nitrogen cycle intermediates present in the studied wastewater.

Anaerobic Treatment of Food Waste with Biogas Recirculation under Psychrophilic Temperature

Food waste has emerged as a pressing concern, and thus advanced techniques to valorize food waste into nutrition rich materials as well as renewable energy are highly important. The exceptional biodegradability of food waste renders it a highly suitable substrate for anaerobic treatment. This leads to energy production and a reduction in the carbon footprint. Nevertheless, in frigid territories like Canada, the conventional mesophilic anaerobic digestion at 30–40 °C can require substantial amounts of energy. Consequently, this study introduces a new approach to treat food waste at psychrophilic temperatures (1–20 °C). Lower temperatures can negatively impact cellular processes during anaerobic treatment, rendering substrates less accessible to microscopic organisms. To address this challenge associated with lower temperatures, the study introduces an innovative biogas recirculation strategy. The primary objectives of this study are to assess the viability of anaerobic treatment for food waste at psychrophilic temperatures and to investigate the effectiveness of reintroduction of the produced biogas to the anaerobic system in enhancing biomethane generation and stability of the system. Batch experiments were conducted on food waste in various assessments, both with and without biogas recirculation. The outcomes revealed a methane concentration ranging from 68% to 93% when biogas recirculation was employed, whereas without this technique, methane concentration varied between 10% and 45%. Moreover, with biogas recirculation, the reduction in volatile solids reached a maximum of 92%, and there was an 82% decrease in chemical oxygen demand. In conclusion, the utilization of the recirculation of biogas at the psychrophilic temperature range enhanced biomethane production and reduction of volatile solids and chemical oxygen demand. This study underscores the potential of employing anaerobic treatment with reintroduction of produced biogas into the system in cold regions as an economically viable and sustainable choice for treating food waste with nominal energy consumption.

Učinkovitost obrade elektrokoagulacije kombinirane s različitim veličinama čestica prirodnog zeolita

In a previous study, the larger size of synthetic zeolite particles was highlighted as better choice for electrocoagulation combined with zeolite (ECZ). This choice resulted in a smaller rise in pH and temperature, a more significant decline in turbidity as well as chemical oxygen demand (COD), and lower electrode wastage, but with greater damage to the electrode surface. The focus of this study was to determine whether natural zeolite of three different particle sizes has the same effect on the ECZ process. The Taguchi method L9 was employed in planning the experiments, with particle sizes of natural zeolite ranging up to 600 μm, three different electrode materials (carbon steel, aluminium alloy, and sacrificial zinc anode), current density in the range of 0.003–0.018 A cm<sup>–2</sup>, and contact time in the range 10–30 min. The Taguchi optimisation results revealed a more significant decrease in COD and turbidity with the smallest particle size of natural zeolite used (90 µm) and with Al electrodes. Evidently, the zeolite particle size, together with the zeolite composition, had a significant influence on the reduction in COD and turbidity. Anode consumption ranged from 0.0172 to 0.6469 g, with minor cathode consumption evident on all electrode materials. Optical microscopy analysis indicated significant corrosion of the anodes, particularly with the largest natural zeolite particle size of 160–600 µm, while minor corrosion damage was also observed on the cathodes.

New Insight into the Performance and Self-Defensive Responses of the Algal–Bacterial Granular Sludge Process under Cr(VI)-Induced Stress

Algal–bacterial granular sludge, a new biological technology, has been widely recognized due to its highly effective pollutant treatment and energy efficiency. This study investigated the effects of environmental concentrations of Cr(VI) (0.5–2.5 mg/L) on the performance of algal–bacterial granular sludge and self-defensive responses after 90 days of cultivation. The results showed that Cr(VI) affected chemical oxygen demand (COD) decrease, ammonia-N and phosphate removal, with different trends being apparent. A linear decline in COD decrease was observed, whereas an initial decrease and then increase in ammonia-N and phosphate removal took place. Algal–bacterial granular sludge effectively removed Cr(VI) from wastewater through biological adsorption and reduction, showing the potential to treat Cr(VI)-contaminated wastewater. Cr(VI) affected the community abundance of the algal–bacterial granular sludge, in which Chlorophyceae and cyanobacteria were vulnerable under Cr(VI)-induced stress. To reduce the toxicity of Cr(VI), over-produced EPS-PN and antioxidant enzymes (MDA, SOD and CAT) acted as self-defensive responses to resist oxidative damage. This study aimed to conduct a comprehensive environmental sustainability assessment of the algal–bacterial granular sludge process in treating municipal wastewater containing Cr(VI). It is hoped that this study can provide useful information for improved engineering feasibility of algal–bacterial granular sludge.

Reduction in phytotoxicity of a textile wastewater against Vigna radiata using Citrobacter sp. M41 in a bioaugmented packed bed column bioreactor

The current research was carried out to devise a biological strategy to remediate dyes and metal ions from textile wastewater. For this purpose, Citrobacter sp. M41 was isolated from a textile wastewater sample. This strain efficiently decolorized > 90 % of the added reactive black-5 (RB5) dye using yeast extract as a C source at 8.5 pH and 30 °C in mineral salt medium containing a mixture of metals (Pb2+, Ni2+ and Cd2+). Moreover, M41 showed > 90 % decolorization of RB5 beside > 80 % concurrent removal of hexavalent Chromium [Cr(VI)]. Furthermore, the granulated corncob and its biochar bioaugmented with M41 and filled within packed bed column based bioreactors efficiently (>90 %) removed the RB5 and Cr(VI) from a textile wastewater. The M41 bioaugmented corncob biochar resulted into a 60.8 %, 57.8 % and 68.7 % decrease in chemical oxygen demand (COD), electrical conductivity (EC) and total dissolved solids (TDS) of the wastewater, respectively. A phytotoxicity study conducted by using mung bean (Vigna radiata) as a test crop indicated that the treated synthetic wastewater was relatively less toxic as compared with the untreated wastewater. Therefore, it can be concluded that Citrobater sp. M41 is an important bio-resource for treatment of textile effluent polluted with azo dyes and Cr(VI).

Biodegradation of pyrene by bacterial consortia: Impact of natural surfactants and iron oxide nanoparticles

Polycyclic aromatic hydrocarbons (PAHs) are potentially hazardous compounds that could cause a severe impact on many ecosystems. They are very challenging to remove using conventional methods due to their hydrophobic nature. However, this issue can be resolved by utilizing surface-active molecules to increase their bioavailability. In this study, pyrene was chosen as the PAH compound to explore its degradability by the effect of individual bacterial strains (Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3) and mixed consortia (MC) along with natural surfactant derived from Sapindus mukorossi and iron oxide nanoparticles (NPs). Additionally, fatty acids esters, dipeptides, and sugar derivative groups were identified as potent bioactive components of natural surfactants. Various techniques, such as XRD, VSM, TEM, and FE-SEM with EDX, were utilized to characterize the pristine and Fenton-treated iron oxide NPs. The analytical results confirmed that the Fe3O4 crystal phase and spherical-shaped NPs exhibited excellent magnetic properties. The impact of natural surfactants and iron oxide NPs has significantly contributed to the biodegradation process, resulting in a prominent decrease in chemical oxygen demand (COD) levels. Gas chromatography-mass spectrometry (GC-MS) analysis showed that biodegradation systems produced primary hydrocarbon intermediates, which underwent oxidative degradation through Fenton treatment. Interestingly, synthesized iron oxide NPs effectively produced hydroxyl radical (•OH) during the Fenton reaction, which was confirmed by electron paramagnetic resonance (EPR) spectra, and the pristine iron oxide NPs underwent a material transformation observed. The study demonstrated an integrated approach for biodegradation and the Fenton reaction process to enhance the pyrene degradation efficiency (90%) compared to other systems. Using natural surfactants and iron oxide NPs in aquatic environments serves as a crucial platform at the interface of microorganisms and contaminated oil products. This interaction offers a promising solution for PAHs bioremediation.

Efficiency of Rhodopseudomonas faecalis in Increasing Digestion of Substrate in an Anaerobic Digester

An anaerobic Purple Non Sulphur Bacteria (PNSB), Rhodopseudomonas faecalis was utilized as an inoculum to study the efficiency of a biogas digester. A 5 litre capacity anaerobic digester was prepared with 10% feed, 30 days of Hydraulic Retention Time (HRT) was studied using canteen waste as a substrate. Parameters like pH, Temperature, Chemical Oxygen Demand (COD), Total Solids (TS), Volatile Solids (VS) and gas production were analyzed and recorded on every day. It was found that pH was decreased and temperature was varying. Increase in the digestion of the substrates was due to the addition of the bacterium eventually causing decrease in COD, TS & VS, was observed. This has increased the production of biogas in the digester.

Electrocoagulation Combined with Synthetic Zeolite—Does the Size of Zeolite Particles Matter?

Although electrocoagulation combined with zeolite (ECZ) shows higher efficiency in wastewater treatment, the actual contribution of zeolite particle size has not been fully explored. In this work, the influence of particle size of synthetic zeolite SZ (<90, 90–160, and 160–600 μm) on ECZ treatment of compost leachate with very high organic load is investigated together with different electrode materials (Fe, Al, and Zn), current densities (0.003, 0.009 and 0.018 A/cm2), and contact times (10, 20 and 30 min). The results positively highlight that the largest particle size should be used in ECZ, as it leads to a lower increase in pH and temperature, a higher decrease of chemical oxygen demand (COD) and turbidity, and a lower electrode consumption, while causing more damage to the electrode surface. The estimated energy costs ranged from 3.960 kW/m3–1313.657 kW/m3. The Taguchi L9 orthogonal configuration showed the highest COD and turbidity decrease under the conditions of 160–600 µm zeolite particles. The powder X-ray diffractometer (PXRD) analysis shows that interplanar spacing decreases when smaller and medium SZ particle sizes are used, while this effect was not observed with larger zeolite particle size. SEM-EDS shows that oxygen, silicon, and aluminium are the predominant elements in electrogenerated sludge coupled with zeolite.

Bioaugmentation Potential Investigation Using a Phenol Affinity Analysis of Three Acinetobacter Strains in a Multi-Carbon-Source Condition

Bioaugmentation potential and phenol substrate affinity in a multi-carbon-source condition for three Acinetobacter strains (Acinetobacter towneri CFII-87, Acinetobacter johnsonii CFII-99A and Acinetobacter sp. CFII-98) were demonstrated. First, the phenol biodegradation ability of the strains was analyzed in batch experiments with phenol as the sole carbon source. All strains degraded phenol at 100 and 500 mg·L−1 initial concentrations; the maximum specific growth rates were 0.59 and 0.30 d−1 for A. towneri CFII-87, 0.50 and 0.20 d−1 for A. johnsonii CFII-99A, and 0.64 and 0.29 d−1 for A. sp. CFII-98, respectively. For the two tested phenol concentrations, no lag phase was observed for the A. towneri CFII-87 strain, A. sp. CFII-98 presented 4 h and 8 h lag phase, while A. johnsonii CFII-99A presented 3 h and 12 h lag phases. Phenol carbon source dependency of the strains was tested in a multi-carbon-source condition (on phenol-rich synthetic wastewater), both for individual strains and for a consortium prepared as an equal mixture of the three strains. The strains A. towneri CFII-87 and A. sp. CFII-98 and the consortia degraded phenol in 16 h while there was no other significant carbon source consumption during the 48 h trial, as shown by the constant non-phenolic residual chemical oxygen demand (COD) and volatile suspended solids (VSS) concentration after the depletion of phenol. The strain A. johnsonii CFII-99A, however, consumed phenol within 24 h and a further decrease in non-phenolic COD and increase in biomass was also observed upon the depletion of phenol. The highest specific phenol removal rate of 282.11 mg phenol·g VSS∙h−1 was observed in the case of the strain A. towneri CFII-87, followed by A. sp. CFII-98, the consortium and A. johnsonii CFII-99A with 178.84, 146.76 and 141.01 mg phenol·g VSS∙h−1, respectively. Two bacterial strains (A. towneri CFII-87, A. sp. CFII-98) presented a strong affinity to phenol, utilizing it as a primary carbon source, and thus, their use in the bioaugmentation of wastewater bioreactors indicated the viable potential to increase the phenol removal rate of these systems.

Influence of copper and iron transition metals in the photocatalytic activity of titanium dioxide microspheres

This work proposes the combined sol–gel/solvothermal synthesis method to prepare Cu-doped TiO2 and Fe-doped TiO2 microstructures, and further study their photocatalytic activity in the degradation of Eriochrome Black T (EBT) at neutral conditions using a simulated sunlight source. TiO2:at%M (at%=0.25, 0.5, and 1.0; M = Cu or Fe) catalysts were characterized by X-ray diffractometry, Scanning electron microscopy, Diffuse reflectance UV–Vis spectroscopy, Raman spectroscopy, and Brunauer-Emmett-Teller surface area analysis. All synthesized catalysts showed TiO2 anatase phase with spherical morphology and average particle size of 4 to 8 μm. Transition metal doping did not modify the TiO2 anatase phase. TiO2:at%M catalysts exhibited lower bandgap energies than pure TiO2. TiO2:0.5at%Fe showed the lowest bandgap energy (2.87 eV). TiO2 catalysts with a transition metal content of 0.25at% showed a higher surface area compared to the rest of dopant concentrations. The inclusion of the metallic elements in the TiO2 structure enhances the photocatalytic efficiency of the TiO2 anatase under visible light. TiO2:0.25at%Cu showed the highest EBT degradation yields of 90% color removal, 61% total organic carbon (TOC) reduction, and 87% chemical oxygen demand decrease at 180 min. TiO2:0.25at%Cu and TiO2:0.50at%Fe microspheres retained good degradation efficiency for color and TOC removals even after being reused for three cycles.

Some approximations on the effect of the supporting electrolyte towards electrochemical advanced oxidation degradation of Reactive Orange 84 (RO84)

In this paper, some advanced oxidation electrochemical processes such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) to carry out the degradation of the azo dye Reactive Orange 84 (RO84) are presented. For this, boron-doped diamond (BDD) electrodes were used, and different configurations were taken in a stirred tank cell, like BDD/graphite and BDD/BDD. The effect of different operating parameters on the discoloration process was evaluated, including the concentration of the supporting electrolyte, namely 50 and 75 mM of Na2SO4, along with 50 mM NaCl and mixtures of Na2SO4 + 25 mM NaCl. The effect of the applied current density at 25, 50, and 100 mA cm−2 over the loss of color was also analyzed using initial RO84 concentrations of 100 and 200 mg/L. The production of free radicals was evaluated in the bulk solution. The decrease in chemical oxygen demand (COD) was determined and the evolution of oxalic acid, a nontoxic, short-chain carboxylic acid was quantified as a final product of all treatments by using ion-exclusion high-performance liquid chromatography.

Biological treatment and microbial composition of landfill leachate using a compost process in an airlift bioreactor

Landfill leachate (LL) contains a large amount of toxic compounds and its treatment is currently a matter of concern. In this work, an adapted compost in different airlift bioreactors was used to depurate a complex, toxic and old landfill leachate without treatment (raw leachate) and after pretreatments (coagulation/flocculation; coagulation/flocculation and filtration; coagulation/flocculation, filtration and photo-Fenton process). After the complete pretreatments, a high removal of organic matter was achieved, with a global removal of chemical oxygen demand (COD) and humic acids of 72.4% and 83.4%, respectively; besides, copper and iron in the landfill leachate presented a total removal of 91.1% and 65.8%, respectively. On the other hand, after the contact of raw leachate with compost in the airlift, there was a decrease of COD, copper and iron, while for humic acids there was a slight increase. The same trend was observed when the leachate was submitted to the different pretreatments and subsequently subjected to the biologic process with compost. The respirometric analyses showed that the raw leachate was toxic, although this tendency decreased along the treatments, with inhibition values of 41.8%, 27.5%, 22.0% and 12.1% for raw and pretreated leachate (by coagulation/flocculation, filtration and photo-Fenton processes), respectively. Also, in order to improve our knowledge about the composition of the microbial assemblages in compost samples and their possible role in pollutants removal from LL, we analysed samples from both an adapted and a non-adapted compost before and after being in contact with the raw leachate by applying Illumina sequencing of the 16S rRNA gene. Bacteroidota, Proteobacteria, Firmicutes, Spirochaetota and Deinococcota were the most abundant phyla in all samples, being present in the 50 most abundant Amplified Sequence Variants (ASVs) of the study, which represented 56.5% of the total analysed sequences and were considered as our core community. Chryseolinea, Herbinix, Proteiniphilum, Pseudomonas and Sphaerochaeta seemed to be the most resilient genera when the compost was in contact to LL. Moreover, our results showed that the metabolisms related to chemoheterotrophy, fermentation and the nitrogen cycle were the most relevant in all samples. In general, the microbial community was able to adapt to adverse conditions and remove pollutants, as heavy metals.

Photocatalytic degradation of remdesivir nucleotide pro-drug using [Cu(1-methylimidazole)4(SCN)2] nanocomplex synthesized by sonochemical process: Theoretical, hirshfeld surface analysis, degradation kinetic, and thermodynamic studies

The first ultrasonic synthesis of [Cu(L)4(SCN)2] (L = 1-methylimidazole) nanocomplex was carried out under ultrasonic irradiation, and its photocatalytic performance for the degradation of remdesivir (RS) under sunlight irradiation was comprehensively investigated for the first time in this study. The physicochemical properties of the synthesized photocatalyst were examined by Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. The band gap of the synthesized [Cu(L)4(SCN)2] nanocomplex was determined to be 2.60 eV by the diffuse reflectance spectroscopy method using Kubelka-Munk formula. The photocatalytic performance of nanocomplex was examined for the removal of remdesivir under sunlight from water for which the results indicated that an amount of 0.5 gL−1 of the [Cu(L)4(SCN)2] nanocomplex was sufficient to remove more than 96% remdesivir from its 2 mg L−1 concentration within 20 min, at pH = 6. The kinetic data showed that the photodegradation onto the [Cu(L)4(SCN)2] nanocomplex has a high correlation (0.98) with the pseudo-second-order kinetic model. The decrease in chemical oxygen demand (COD) (from 70.5 mg L−1 to 36.4 mg L−1) under optimal conditions clearly confirmed the mineralization of the RS drug. The values of ΔS° (−0.131 kJ mol−1 K−1) and ΔH° (−49.750 kJ mol−1) were negative, indicating that the adsorption process was spontaneous and more favorable in lower temperatures. Moreover, the RS structure in the open shell state and the high HOMO and LUMO gaps based on the M06/6-31 + G (d) level of theory may be a confirmation of this fact. In addition, the Hirshfeld surface analysis (HSA) of the crystal packing of the prepared complex was discussed in detail to evaluate the interactions between the crystal packings. The results of this study confirm that the [Cu(L)4(SCN)2] nanocomplex can be successfully used for the photodegradation of pharmaceutical contaminants.

Integrated Photocatalytic Oxidation and Adsorption Approach for the Robust Treatment of Refinery Wastewater Using Hybrid TiO2/AC

This study reports the removal of hydrocarbon (HC) pollutants from petroleum refinery wastewater by integrated photocatalytic oxidation and adsorption using a TiO2/AC hybrid material. The hybrid adsorbent/catalyst was prepared by the impregnation of TiO2 over AC and characterized by FTIR, SEM, EDX, and XRD analyses. Under the optimized reaction conditions of pH 3, 30 °C, and 1000 mg TiO2/AC per 500 mL of sample in 50 min, the integrated photocatalytic oxidation-adsorption achieved a net percentage removal of benzene, toluene, aniline, and naphthalene of 91% from model HC solutions. Under these conditions, for the treatment of real refinery wastewater, TiO2/AC caused a 95% decrease in chemical oxygen demand (COD). The integrated photocatalytic oxidation and adsorption using TiO2/AC showed a clear advantage over the individual adsorption and photocatalytic oxidation using AC and TiO2, whereby about the same level of removal of model HCs and a decrease in the COD of refinery wastewater was attained in 105 min and 90 min, respectively, utilizing larger adsorbent/catalyst dosages. GC-MS analysis revealed that during the integrated process of adsorption-photocatalytic oxidation, all the parent HCs and oxidation byproducts were completely removed from the refinery wastewater. Based on the outstanding performance, cost-effectiveness, and environmental greenness, the newly designed TiO2/AC via the integrated adsorption-photocatalytic oxidation can be counted as an effective alternative route for the large-scale processing of refinery wastewater.