Improvement Of Biodegradability Research Articles

A novel strategy combining hydrogenotrophic methanogens' bioaugmentation and biochar biostimulation for simultaneous polycyclic aromatic hydrocarbon biodegradation and bioenergy recovery.

A novel strategy combining bioaugmentation using methanogenic archaea and biostimulation using biochar was proposed for the first time to obtain simultaneous improvement of mixed PAHs' anaerobic biodegradation and bioenergy production. The results showed that the addition of PHAs immediately resulted in inhibition in methane production and accumulation of VFA, indicating that PHAs are more toxic to methanogens than the acetogenic bacteria. The coupling of biochar with hydrogenotrophic methanogen alleviated the inhibitory effects of PAHs, allowing the anaerobic fermentation system to recover its methane production capability rapidly. Compared to the Fe3+ + bioaugmentation group, the biochar + bioaugmentation group exhibited a 7.5% higher restored cumulative methane production. This coupling strategy ultimately facilitated the degradation of most PAHs, achieving a removal rate of over 90%. Moreover, the coupled biochar and bioaugmentation induced significant changes in the archaeal community structure. Direct interspecies electron guilds (i.e., Streptococcus and Methanosarcina) were enriched in the presence of biochar and bioaugmentation, responsible for prominent PAH removal and methane recovery. This study demonstrated the feasibility of simultaneous PAH biodegradation and bioenergy production using electron acceptor and enriched microorganisms.

Thermal hydrolysis pretreatment of wastewater biosolids: Modelling the impact of the aerobic sludge age

This study investigates the impact of thermal hydrolysis pretreatment (THP) on the characteristics of wastewater biosolids, methane production, anaerobic biodegradability, and recycled sidestream nitrogen loads, as a function of the sludge age of the activated sludge (AS) system through a series of BioWin simulations of 3 different process configurations at sludge ages of 5, 10, 15, 20, 30, and 60 d, with and without thermal hydrolysis. BioWin's anaerobic digester and thermal hydrolysis units were calibrated by adopting and identifying various kinetic and operational parameters from the available literature and through series of full-scale plant simulations. Thermal hydrolysis improved the hydrolysis rates of the biosolids by 181%. Improvements in anaerobic biodegradability, mainly due to the conversion of endogenous products, ranged from 14% to 67% at sludge ages of 5–15 d. At sludge ages of 20–60 d, anaerobic biodegradability improved by 59% to 186% depending on the process configuration. At sludge ages of 15–60 d, methane production was relatively stable and insensitive to the biosolids composition. Despite the increase in the recycled nitrogen load by 42% to 127%, it only constituted 13% of the influent nitrogen load. Effluent ammonia concentrations remained unchanged and effluent nitrates concentrations only increased by 1.4 to 2 mg N/L, maintaining effluent standards without additional sidestream treatment.

4-Chloro-2-methylphenoxyacetic acid photo-reduction with sulfite excitation under UV irradiation: Kinetics, energy consumption, operational variables and toxicology with Daphnia magna

4-chloro-2-methylphenoxyacetic acid (MCPA) is persistent and emerging organic substances that cannot be removed by bio-degradation and simply enter the environment. Therefore, for its photo-reduction, new methods are needed, including advanced photo- reduction process. This work deals with use of MCPA photo-reduction process based on sulfite excitation under UV irradiation. The optimal pH was 9 and molar ratio 1:1 MCPA: Sulfite, and complete photo-reduction of MCPA was reached after 15 min reaction time. The effect of various parameters were optimized using one factor at time (OFAT). In kinetic investigation, reaction constant (kobs) reduced from 0.2794 to 0.1645 min−1 when MCPA concentration increase from 5 to 25 mg L−1. In addition, the reaction rate (robs) increased 1.397 to 4.1125 mg L−1 min−1. Also, EEO was determined by kinetics and IUPAC methods, which showed that the quantity of energy consumption increases with increasing MCPA concentration. 2-(o-tolyloxy)acetic acid, 1-ethoxy-2,4-dimethylbenzene, toluene, (E)− 2-(prop-l-en-l-yloxy)acetic acid, (E)− 1-ethoxyprop-1-ene, and (E)− 1-ethoxyprop-1-ene identified as intermediates. Improvement of biodegradability was investigated with tow indicators include AOS and COS and shows that with the passage of time, the improvement of degradability is noticeable. For explored the mineralization rate, COD, TOC removal efficiency reach > 99%, 74.7%, and 62%, respectively after 120 min reaction time. The acute toxicity test by Daphnia magna was utilized to assess the toxicity of UV/Sulfite process effluent, results showed that EC50 (96-hour) and toxicity unit (TU) were equal to 10.53 mg L−1 and 9.94 TU in raw solution of MCPA and 93.50 mg L−1 and 1.07 TU in treated solution respectively, which the effluent from the process was reduced significantly than the raw solution of pollutant. It can be disclosed that the UV/Sulfite process has a good performance in pollutant conversion to simple intermediate and improving biodegradability as well as wastewater detoxification to reach environmental standards.

In situ carbonization metamorphoses porous silica particles into biodegradable therapeutic carriers of lesser consequence on TGF-β1 mediated fibrosis.

Extensive modifications have been made to the synthesis protocol for porous silica particles to improve the shape, size and yield percentage, but problems associated with improvement in biodegradability and decrease in chances to induce side effects still remain a concern. To circumvent these limitations, a facile modification strategy has been employed through in situ carbonization of porous silica particles. Herein, carbon particles were integrated within porous silica core-shell particles (Si-P-CNPs) during the synthesis process and found to preserve the ordered structural morphology. Curcumin was used as a model drug for loading in prepared Si-P-CNPs whereas lung cancer cells were used as a model system to study the in vitro fate. These Si-P-CNPs showed improved drug loading, drug effectivity, biodegradability and avoidance of interaction with transforming growth factor β1 (TGF-β1) indicating the possibility of reducing the chances of lung fibrosis and thereby enhancing the safety profile over conventional porous silica particles.

Optimisation, modelling and mechanism of photocatalytic degradation of sofosbuvir antiviral by TiO2 nanoparticles coupled with biological treatment

ABSTRACT The overarching objective of this research endeavour was to develop an integrated approach to the complete removal and breakdown of the antiviral compound sofosbuvir. To accomplish this, a two-fold strategy was employed, involving a heterogeneous photocatalysis process coupled with subsequent biological treatment. Leveraging the versatile TiO2-P25 nanoparticles, a meticulous optimisation was carried out using the Box-Behnken methodology, strategically considering the interplay of three pivotal independent variables: pH, initial molecule concentration, and catalyst concentration. This optimisation aimed not only to augment the degradation of sofosbuvir but also to enhance its COD removal. The complex influence of these factors was mathematically encapsulated in a second-order polynomial equation, offering valuable insights into the process dynamics. COD removal and optimal parameters for degradation were a pH of 6.8, a catalyst dosage of 1 g L−1, and an initial molecule concentration of 0.1 mM under a 125 W high-pressure mercury lamp. The efficiency of elimination for the degradation was 100% at 120 min and for the COD removal extinguished 99.44% at 6 h. Sofosbuvir has a rapid degradation, COD removal degree is lower, which means the presence of intermediate compounds more difficult to treat by photocatalysis. Thus, the viability of implementing a link between the nanoparticles TiO2-photocatalysis as a biodegradability improvement pretreatment with the biological process has been studied as an essential activity to enhance treatment efficiency while reducing energy use and treatment times. combination of photocatalysis with a biological treatment improves the treatment. The density functional theory (DFT) approach was applied to better understand the mechanism of sofosbuvir degradation and to examine the impact of different degradation sites. Mechanism Analysis of the photoproducts and photoproduct intermediates was identified by HPLC-MS. However, a 120 min BOD5/COD ratio (COD, chemical oxygen demand; BOD, biochemical oxygen demand) of ≥0.4 results from the degradation of sofosbuvir by TiO2.

Anodic oxidation of ciprofloxacin antibiotic and real pharmaceutical wastewater with Ti/PbO2 electrocatalyst: Influencing factors and degradation pathways

This study investigated the impact of operational variables including current density, solution pH, sodium sulfate electrolyte concentration, initial pollutant concentration, and reaction time on ciprofloxacin (CIP) anodic oxidation and its COD removal by Ti/PbO2 electrocatalyst. Ti/PbO2 anode was prepared by electrochemical method and its characteristics were determined using SEM, EDX-map, XRD, and linear sweep voltammetry (LSV) techniques. Under optimal conditions, the removal rate of CIP and COD at the initial concentration of 15 mg/L of the pollutant after 75 min of reaction was 92 % and 88.8 %, respectively. CIP mineralization was confirmed by evaluating its UV–vis spectra and cyclic voltammetry (CV) curves during the process. Considering the degradation intermediates identified by LC-MC analysis, the main reactions in CIP mineralization pathways were discussed in detail. Finally, the improvement of biodegradability of pharmaceutical wastewater during anodic oxidation treatment was evaluated. The results indicated that the biodegradability of wastewater significantly increased from BOD/COD = 0.18 for raw wastewater to BOD/COD = 0.42 for treated wastewater. The results showed that anodic oxidation with Ti/PbO2 electrocatalyst can be a practical method of treating wastewater that contains resistant and toxic pharmaceutical compounds.

Structure prediction, docking studies and molecular cloning of novel Pichia kudriavzevii YK46 metalloprotease (MetPr) for improvement of feather waste biodegradation

This study addresses the environmental risks associated with the accumulation of keratin waste from poultry, which is resistant to conventional protein degradation methods. To tackle this issue, microbial keratinases have emerged as promising tools for transforming resilient keratin materials into valuable products. We focus on the Metalloprotease (MetPr) gene isolated from novel Pichia kudriavzevii YK46, sequenced, and deposited in the NCBI GenBank database with the accession number OQ511281. The MetPr gene encodes a protein consisting of 557 amino acids and demonstrates a keratinase activity of 164.04 U/ml. The 3D structure of the protein was validated using Ramachandran's plot, revealing that 93% and 97.26% of the 557 residues were situated within the most favoured region for the MetPr proteins of template Pichia kudriavzevii strain 129 and Pichia kudriavzevii YK46, respectively. Computational analyses were employed to determine the binding affinities between the deduced protein and beta keratin. Molecular docking studies elucidated the optimal binding affinities between the metalloprotease (MetPr) and beta-keratin, yielding values of − 260.75 kcal/mol and − 257.02 kcal/mol for the template strains Pichia kudriavzevii strain 129 and Pichia kudriavzevii YK46, respectively. Subsequent molecular cloning and expression of the MetPr gene in E. coli DH5α led to a significantly higher keratinase activity of 281 ± 12.34 U/ml. These findings provide valuable insights into the potential of the MetPr gene and its encoded protein for keratin waste biotransformation, with implications for addressing environmental concerns related to keratinous waste accumulation.

Submerged arc plasma treatment of landfill leachate with a high proportion of refractory organics: Degradation performance and biodegradability enhancement

Efficient treatment of landfill leachate remains a challenge because of the load and highly stable recalcitrant organics. Herein, pre-treatment of real stabilized leachate was realized in a submerged arc plasma (SAP) reactor to which microbubbles with different carrier gases (air, N2, and O2) were introduced to preserve the subsequent biological process. We performed a detailed parametric analysis (applied voltage, electrode material, carrier gas, and initial pH) to determine the optimum operational conditions of organics degradation and leachate biodegradability improvement. Besides, degradation kinetics, reaction mechanism, and electrical energy consumption were studied during the SAP process. Ion exchange resin was initially used to effectively reduce the ionic strength of the bulk solution to allow expanding the plasma discharge area. The biodegradability of leachate was outstandingly enhanced, as reflected by an increase in BOD5/COD ratio from 0.08 to 0.68 in O2 discharge within 120 min. Meanwhile, stainless-steel as a grounded electrode outperformed aluminum, brass, and copper. The SAP also exhibited excellent performance for organics decomposition, which was found to follow second-order and approximately pseudo-second-order kinetics. Meanwhile, the possible mechanism of organics destruction was proposed based on COD measurements and reactive species trapping experiments, demonstrating the prevailing contribution of H2O2 and 1O2, among others. Nonetheless, the SAP process of leachate treatment required relatively high energy consumption (18,400 kWh/m3). The study demonstrated an effective and robust pre-treatment process for the subsequent bioremediation of landfill leachate containing chemically stable and recalcitrant organics not treatable by conventional techniques.

Molecular design of environment-friendly amide herbicide substitutes with high efficacy, low phytotoxicity and medication safety

The primary goal of this investigation was to formulate an ecologically sustainable alternative to amide herbicides (AHs) characterized by robust herbicidal effectiveness, minimal corn phytotoxicity, and commendable pharmaceutical safety. We employed comparative molecular similarity index analysis (CoMSIA), a three-dimensional quantitative structure-activity relationship (3D-QSAR) model, which systematically outlined parameters such as herbicidal effectiveness, corn phytotoxicity, and AHs biodegradability. Subsequently, after thorough evaluation, we carefully selected a group of fourteen stable AH-substitute compounds known for their safety and environmental compatibility, considering aspects like pharmacokinetics, toxicokinetics, functional properties, and environmental friendliness. This resulted in a significant increase in herbicidal effectiveness, ranging from 21.64% to 34.07%, alongside a decrease in corn phytotoxicity within the range of 12.19–20.87%. Furthermore, we achieved an improvement in biodegradability, measured within the spectrum of 4.92–9.40%. Importantly, these changes also correlated with the reduction of hepatotoxicity, mutagenicity, and cutaneous health risks. Finally, we delved into the mechanisms underlying the improved herbicidal effectiveness, reduced corn phytotoxicity, and enhanced biodegradability of AHs substitutes through molecular docking and analysis of amino acid interactions. The investigation concluded that non-covalent forces governing the interaction between AHs substitutes and receptor proteins are crucial in determining herbicidal effectiveness, corn phytotoxicity, and biodegradability. Specifically, Van der Waals and electrostatic forces emerged as key factors governing the binding affinities of AH molecules with receptor proteins, both before and after modification. In summary, this study introduces innovative approaches in the field of agricultural chemical weeding technology and provides a theoretical framework for the environmentally responsible management of AHs herbicides.

Biodegradability enhancement of waste lubricating oil regeneration wastewater using electrocoagulation pretreatment.

As a sustainable management of fossil fuel resources and ecological environment protection, recycling used lubricating oil has received widespread attention. However, large amounts of waste lubricating-oil regeneration wastewater (WLORW) are inevitably produced in the recycling process, and challenges are faced by traditional biological treatment of WLORW. Thus, this study investigated the effectiveness of electrocoagulation (EC) as pretreatment and its removal mechanism. The electrolysis parameters (current density, initial pH, and inter-electrode distance) were considered, and maximal 60.06% of oil removal was achieved at a current density of 15mA/cm2, initial pH of 7, and an inter-electrode distance of 2cm. The dispersed oil of WLORW was relatively easily removed, and most of the oil removal was contributed by emulsified oil within 5-10μm. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that effective removal of the biorefractory organic compounds could contribute to the improvement of biodegradability of WLORW. Thus, the 5-day biochemical oxygen demand/chemical oxygen demand ratio (BOD5/COD) was significantly enhanced by 4.31 times, which highly benefits future biological treatment. The routes of WLORW removal could be concluded as charge neutralization, adsorption bridging, sweep flocculation, and air flotation. The results demonstrate that EC has potential as an effective pretreatment technology for WLORW biological treatment.

Efficient and eco-friendly mixed bacterial consortium for petroleum wastewater treatment: Effect of the bio-augmentation and biosurfactant addition on hydrocarbon biodegradation

In the present investigation, we aimed to study biological petroleum wastewater treatment. A bioprocess based on the use of a mixed bacterial consortium along with the addition of Biosurfactant (BioS) and bioaugmentation with BioS producing strains were evaluated. The consortium was the combination of two bacterial strains with the capacity to metabolize hydrocarbons, Baci and B201. Two other strains BH1 and BSS2 selected for their ability to degrade hydrocarbons as well as to produce BioS were also exploited. The effect of ex-situ and in-situ produced BioS on hydrocarbon biodegradation were compared. Obtained results demonstrated a moderate capacity to remove crude oil from contaminated water of about 47% for the consortium. The best improvement of hydrocarbon biodegradation of about 84% was obtained when adding BH1 derived BioS solely. However, ex-situ produced BioS exhibited better results. Regarding the wastewater characteristics, we note a decrease of the COD/BOD5 Ratio to reach 2.64. Thus, the wastewater became easily biodegradable. The described bioprocess is of great interest for the bioremediation of petroleum effluents. BioS addition as well as bioaugmentation enhanced crude oil removal.

Influence of microbial biomass content on biodegradation and mechanical properties of poly(3-hydroxybutyrate) composites

Biodegradation rates and mechanical properties of poly(3-hydroxybutyrate) (PHB) composites with green algae and cyanobacteria were investigated for the first time. To the authors knowledge, the addition of microbial biomass led to the biggest observed effect on biodegradation so far. The composites with microbial biomass showed an acceleration of the biodegradation rate and a higher cumulative biodegradation within 132 days compared to PHB or the biomass alone. In order to determine the causes for the faster biodegradation, the molecular weight, the crystallinity, the water uptake, the microbial biomass composition and scanning electron microscope images were assessed. The molecular weight of the PHB in the composites was lower than that of pure PHB while the crystallinity and microbial biomass composition were the same for all samples. A direct correlation of water uptake and crystallinity with biodegradation rate could not be observed. While the degradation of molecular weight of PHB during sample preparation contributed to the improvement of biodegradation, the main reason was attributed to biostimulation by the added biomass. The resulting enhancement of the biodegradation rate appears to be unique in the field of polymer biodegradation. The tensile strength was lowered, elongation at break remained constant and Young’s modulus was increased compared to pure PHB.

High-throughput experimentation for discovery of biodegradable polyesters

The consistent rise of plastic pollution has stimulated interest in the development of biodegradable plastics. However, the study of polymer biodegradation has historically been limited to a small number of polymers due to costly and slow standard methods for measuring degradation, slowing new material innovation. High-throughput polymer synthesis and a high-throughput polymer biodegradation method are developed and applied to generate a biodegradation dataset for 642 chemically distinct polyesters and polycarbonates. The biodegradation assay was based on the clear-zone technique, using automation to optically observe the degradation of suspended polymer particles under the action of a single Pseudomonas lemoignei bacterial colony. Biodegradability was found to depend strongly on aliphatic repeat unit length, with chains less than 15 carbons and short side chains improving biodegradability. Aromatic backbone groups were generally detrimental to biodegradability; however, ortho- and para-substituted benzene rings in the backbone were more likely to be degradable than metasubstituted rings. Additionally, backbone ether groups improved biodegradability. While other heteroatoms did not show a clear improvement in biodegradability, they did demonstrate increases in biodegradation rates. Machine learning (ML) models were leveraged to predict biodegradability on this large dataset with accuracies over 82% using only chemical structure descriptors.

Mineralization and biodegradability improvement of textile wastewater using persulfate/dithionite process

Mineralization and biodegradability improvement of textile wastewater using persulfate/dithionite process

Algae-mediated bioremediation of ciprofloxacin through a symbiotic microalgae-bacteria consortium

The ciprofloxacin treating via microalga and its microalgae-bacteria consortium was investigated for discussing the potential application of microalgae-mediated bioremediation. As results, the maximum removal efficiency of ciprofloxacin by pure microalgae and the consortium was 87.5 ± 3.5 % (5 mg/L) and 96.1 ± 0.07 % (40 mg/L), respectively. The consortium enhanced the degradation rate to 0.81 d−1 compared with the pure microalgae (0.27 d−1). To reveal the symbiotic mechanism, extracellular polymeric substances, pigments contents, antioxidant enzymes and symbiotic bacterial community were analyzed. The malondialdehyde content in the pure microalgae (1622.6 ± 38.7 nmol/mg protein) was higher than that in the consortium (298.34 ± 2.4 nmol/mg protein), and there were obvious chlorophyll b accumulations (approximately 90 %) in consortium. In addition, the symbiotic bacteria had a positive effect on microalgal secretion of fulvic acid-type components. As mechanism, symbiotic bacteria improved ciprofloxacin biodegradation by reducing cell damage and secreting fulvic acid. The presence of Phycisphaeraceae and Rhizobiaceae, nitrogen fixation bacteria, in the consortium suggest that improvement of ciprofloxacin biodegradation might be associated with nitrogen co-metabolism as well. Collectively, this work elucidates the mechanism of enhancing elimination of ciprofloxacin via microalgae-bacteria consortium and accelerates development of microalgae-mediated aquaculture tailwater bioremediation.

Using a promising biomass-based biochar in photocatalytic degradation: highly impressive performance of RHB/SnO2/Fe3O4 for elimination of AO7.

The release of industrial dyes into the environment has recently increased, resulting in harmful effects on people and ecosystems. In recent years, the use of adsorbents in photocatalytic nanocomposites has attracted significant interest due to their low cost, efficiency, and eco-friendly physical and chemical characteristics. Herein, Acid Orange 7 (AO7) removal was investigated by photocatalytic degradation using Rice Rusk Biochar (RHB), Tin (IV) Oxide (SnO2), and Iron Oxide (Fe3O4) as heterogeneous nanocomposite. After the preparation of RHB, the nanocomposite was synthesized and characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET), and Fourier-Transform Infrared Spectroscopy (FT-IR). To optimize the elimination of AO7 by the One-Factor-At-a-Time (OFAT) method, effective parameters including mixing ratio (RHB:SnO2:Fe3O4), dye concentration, solution pH, and nanocomposite dose were studied. The results showed that the removal efficiency of AO7 after 120min under the optimal mixing ratio of 1:1.5:0.6, dye concentration of 75mg/l, solution pH of 4, and nanocomposite dose of 0.7g/l was 92.37%. Moreover, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal rates were obtained at 82.22 and 72.22%, respectively. The Average Oxidation State (AOS) and Carbon Oxidation State (COS) of the AO7 solution were increased after the process, indicating biodegradability improvement. Various scavenger effects were studied under optimal conditions, and the results revealed that O2- and H+ reactive species play a crucial role in the photocatalytic degradation of AO7. The reusability and stability of nanocomposite were tested in several consecutive experiments, and the degradation efficiency was reduced from 92 to 79% after five consecutive cycles. It is expected that this research contributes significantly to the utilization of agricultural waste in photocatalytic nanocomposites for the degradation of environmental pollutants.

Micro-aeration assisted with electrogenic respiration enhanced the microbial catabolism and ammonification of aromatic amines in industrial wastewater

Improvement of refractory nitrogen-containing organics biodegradation is crucial to meet discharged nitrogen standards and guarantee aquatic ecology safety. Although electrostimulation accelerates organic nitrogen pollutants amination, it remains uncertain how to strengthen ammonification of the amination products. This study demonstrated that ammonification was remarkably facilitated under micro-aerobic conditions through the degradation of aniline, an amination product of nitrobenzene, using an electrogenic respiration system. The microbial catabolism and ammonification were significantly enhanced by exposing the bioanode to air. Based on 16S rRNA gene sequencing and GeoChip analysis, our results indicated that aerobic aniline degraders and electroactive bacteria were enriched in suspension and inner electrode biofilm, respectively. The suspension community had a significantly higher relative abundance of catechol dioxygenase genes contributing to aerobic aniline biodegradation and reactive oxygen species (ROS) scavenger genes to protect from oxygen toxicity. The inner biofilm community contained obviously higher cytochrome c genes responsible for extracellular electron transfer. Additionally, network analysis indicated the aniline degraders were positively associated with electroactive bacteria and could be the potential hosts for genes encoding for dioxygenase and cytochrome, respectively. This study provides a feasible strategy to enhance nitrogen-containing organics ammonification and offers new insights into the microbial interaction mechanisms of micro-aeration assisted with electrogenic respiration.

Study on Biodegradability and Mechanism of Cyanoethylated Waste Paper

With white pollution caused by petroleum plastics becoming an environmental issue of global concern, biodegradable plastics have become a research hotspot, and biodegradable materials made from plants have been attracting attention. Based on previous studies, this paper studied the biodegradability of thermoplastic cyanoethylated waste paper (CWP) by microbial experiment, and preliminarily explored the degradation mechanism. The results showed that: (1) the biodegradability of CWP was better than that of waste paper, and the higher the degree of modification, the better the biodegradability of CWP; under the action of Trichoderma reesei, the degradation rate of CWP containing 20.79% nitrogen was about 24% after 144 h (hours) of degradation; (2) The degradation rate of CWP was about 45% after 144 hours degradation by microbial complex bacteria, which was mainly due to the synergistic effect of cellulose degrading enzymes secreted by microbial degrading bacteria, which greatly improved the degradation rate of CWP. (3) The improvement of biodegradability of CWP was mainly due to the change of the morphology of the fibers by cyanoethylation reaction, which increased the contact surface and destroyed the crystal structure of the waste paper fibers. The increase of the amorphous region and the distance between the crystal planes was more conducive to the cellulase entering into the CWP, thus improving the degradation rate. (4) Structural analysis of CWP before and after degradation showed that microbial degradation bacteria destroyed C≡N bond and formed hydrocarbon bond, and further destroyed the crystal structure of CWP without changing the crystal form of the fiber.

Bismuth-doped 3D carbon felt/PbO2 electrocatalyst for degradation of diuron herbicide and improvement of pesticide wastewater biodegradability

A bismuth-doped three-dimensional networked carbon felt/PbO2 (CF/Bi-PbO2) anode was developed for the electrocatalytic degradation of diuron and treatment of real pesticide wastewater. The prepared PbO2 anodes were characterized by FESEM, XRD, EDX, BET-BJH, accelerated lifetime test, LSV, CV and EIS. Bi doping in the PbO2 matrix significantly increased the electrochemical active area (3.17 vs. 1.57 m2 g−1), oxygen evolution potential (2.3 vs. 1.95 V) and service time (143 vs. 76 h) of CF/Bi-PbO2 anode compared to pristine CF/PbO2. The results showed that the optimized degradation efficiency of diuron by CF/Bi-PbO2 anode at pH 5 and a current density of 15 mA cm−2 after 25 min of reaction is 97.6 %. However, it took 50 min to remove COD with 98.7 % efficiency. The possible pathways of electrocatalytic degradation of diuron were discussed using HPLC-mass data. The electrocatalytic performance of PbO2 anodes was compared under optimal conditions for real pesticide wastewater treatment. Accordingly, the kinetic constant of COD removal by Bi-doped anode (0.0101 min−1) was about 2.4 times higher than pristine PbO2 (0.0043 min−1). The biodegradability index (BOD/COD ratio) of pesticide wastewater after 180 min of treatment by CF/Bi-PbO2 and CF/PbO2 anodes was 0.62 and 0.29, respectively, which shows that the wastewater treated with Bi-doped anode is completely biodegradable.

Study on the biodegradability improvement of 2,4 dinitrophenol in wastewater using advanced oxidation/reduction process with UV/SO3/ZnO.

2,4-Dinitrophenol (2,4-DNP) is a toxic compound that is widely used in many industrial and agricultural processes. This compound has low biodegradability in the environment due to its aromatic structure, and it is unsuccessfully eliminated by other chemical methods. Therefore, in this study, an integrated oxidation and reduction method was used to remove 2,4-DNP from the aqueous medium, in order to simultaneously use the benefits of oxidizing and reducing radicals in 2,4-DNP degradation. 2,4-DNP degradation was modeled by response surface methodology (RSM) and central composite design (CCD). According to the results obtained from RSM, the optimal values for the studied parameters were obtained at pH = 8.9, time = 25 min, ZnO dose = 0.78 g/L, SO3 = 1.89 mmolL-1 and 2,4-DNP concentration = 5 mg/L. Also, the removal efficiency with the integrated process was 3 to 4 times higher than the advanced oxidation or advanced reduction processes alone. Analysis of the data showed that at the time of the study, 2,4-DNP had been converted to linear hydrocarbons, and increased periods of time were required for complete mineralization. A decrease in the first-order model rate constant (kobs) and an increase in 2,4-DNP degradation rate (robs) were observed at higher DNP concentrations.