Maximum Removal Rate Research Articles

The influence of cysteine in transformation of Cd fractionation and microbial community structure and functional profile in contaminated paddy soil

Remediating cadmium (Cd) contaminated paddy soil is vital for agroecology, food safety, and human health. Soil washing is more feasible to reduce remediation method due to its high efficiency. However, green, low-cost and more efficient washing agents are still required. In this study, we investigated the ability of cysteine as a washing agent for soil washing to remove Cd from contaminated paddy soil. Through a batch experiment, we evaluated the removal efficiency of cysteine as a washing agent by comparing their removal rate with that of a microbial inoculant and sulphuric acid as other washing agents. The transformation of Cd fractionation and microbial community structure and functional profile in paddy soils after cysteine leaching was studied by using sequential extraction and high-throughput sequencing. Results showed that cysteine had better efficiency in the removal of Cd from paddy soil in comparison to sulphuric acid and the microbial inoculant, and could achieve a maximum removal rate of 97 % Cd in paddy soil. Cysteine decreased the proportion of Cd in the exchangeable fraction, carbonate bound fraction, iron and manganese bound fraction, and organic matter bound fraction and was best for the removal of the residual fraction, which contributed to its higher Cd removal ability. Considering the economic benefits of the reagents used, cysteine was shown to be economically feasible for use as a leaching agent. In addition, cysteine could significantly increase the relative abundance of Thermochromatium, Sideroxydans, Streptacidiphilus, and Frankia which promoted the nitrogen and sulfur metabolism in the paddy soil. In summary, this study revealed that cysteine was readily available, cheap, non-toxic, highly efficient, and even has fertilizing properties, making it eco-friendly and ideal for remediation of Cd-contaminated paddy soils. Besides, the health of paddy soils would also benefit from cysteine's promotion of microbial nitrogen and sulfur metabolism.

Mathematical modeling and optimization of machining parameters in CNC turning process of Inconel 718 using the Taguchi method

To remain competitive, machining processes must be optimized to provide increased productivity and higher quality products. The aim of most efforts in these machining processes is to establish the optimal parameters to obtain the maximum material removal rate with minimum surface roughness which represents two of the main quality responses. This paper focuses on the optimization of process parameters in dry turning of Inconel 718, a nickel-based superalloy with PVD-coated carbide inserts based on single-objective optimization Taguchi technique, desirability function approach combined with response surface methodology (RSM), which is known as the multi-objective Desirability Optimization Methodology (DOM). Taguchi’s orthogonal-array design L9 (33) and ANOVA analysis of variance are used to study the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and the dependent output variables i.e., the arithmetic mean deviation of the profile's surface roughness (Ra) and material removal rate (MRR). A regression analysis was used to develop a mathematical model based on the first-order model to predict the Ra and MRR model. Using multiple regression analysis, first order linear prediction model was obtained to find the correlation between surface roughness and MRR with independent variables. In the range of parameters investigated, the obtained mathematical models accurately represent the response index, and the results of the experiments demonstrate that the feed rate and the depth of cut are the most important factors influencing Ra and MRR, respectively. Finally, confirmatory tests proved that Taguchi's method, desirability function approach combined with linear regression models was successful in optimizing turning parameters for minimum surface roughness and maximum MRR.

A Promising Process to Remove Nitrate from Solar Panel Production Wastewater and Meanwhile Generating Electricity

For traditional heterotrophic denitrification technology, organics are usually added as the electron donor for nitrate removal, which increases the operation cost for wastewater treatment. Solar panel production wastewater contains a large amount of nitrate. To decrease the operation cost and reduce CO2 emissions, an iron anode microbial fuel cell (Fe-MFC) was constructed to treat solar panel production wastewater by sequencing batch operation. The results showed that the maximum nitrate removal efficiency reached 99.98% and the maximum removal rate was 0.049 kg·m−3·d−1. The output voltages rose rapidly to 560 ± 10 mV within 2 h and then stabilized at 520 ± 50 mV for about 40 h. Combining the detection of coulombic efficiency, CV curve, q* value and internal resistance; the decrease in denitrification efficiency and electricity generation efficiency probably resulted from the passivation of iron anode and the aging of the cathode biofilm resulted in the efficiency decrease. From the microbial analysis, Chryseobacterium, Thermomonas and Thauera predominated at the end of Fe-MFC operation. Microorganisms that cannot adapt to the autotrophic environment in Fe-MFC died out finally. Periodic replacement of the iron anode and domestication of the bio-cathode were essential to maintain the Fe-MFC efficiency. The Fe-MFC technology was feasible to be used to remove nitrate and generate electricity from solar panel production wastewater. Without organics addition, the Fe-MFC technology was cost-efficient and environmentally friendly, endowing itself with a broad prospect of application.

Optimization pilot scale study on ammonia nitrogen removal by bio filter

In order to obtain the optimal conditions for ammonia nitrogen (AN) wastewater treatment by bio filter (BF), the effects of ratio of carbon to nitrogen (C/N), pH, and hydraulic load (HL) on the AN degradation were studied by Response Surface Methodology (RSM). Central Composite Design (CCD) experiments were conducted, and the response of the AN removal rates were fitted to a second-order polynomial model. The analysis of variance showed that the model was accurate and reliable. Through model fitting, the optimal condition for AN removal was: C/N of 18.95, pH of 7.78, and HL of 1.04 d−1. The maximum AN removal rate predicted by the model was 91.90%, accorded with the experimental verification value of 91.37% under the optimal condition. The research provided valuable demonstration for optimizing process parameters on AN removal in BF.

Efficient Organic Pollutant Removal by Bio/MNs Collaborating with Pseudomonas aeruginosa PAO1

Organic pollution is one of the main sources of environmental pollution, which poses a serious threat to the ecological environment and human health. In this study, we synthesized a composite material consisting of biochar-supported magnetite nanoparticles (Bio/MNs) and collaborated with Pseudomonas aeruginosa PAO1 (P. aeruginosa PAO1) to conduct a bio-chemical composite remediation approach for organic pollution. The results of the scanning electron microscope (SEM) and X-ray diffractometer (XRD) show that Bio/MNs composites have been prepared successfully. Under light conditions, the highest removal rate of organic pollution by Bio/MNs synergistic P. aeruginosa PAO1 reached 81.5%. Gradient experiments revealed a direct correlation between the removal rate of organic pollution and the dosage of P. aeruginosa PAO1, as well as the input of Bio/MNs, within a specific range. Moreover, due to the positively charged nature of organic pollution, its maximum removal rate reaches 98.6% at pH = 11, exhibiting a 1.76-fold increase compared to that at pH = 3. The experimental results show that the collaboration between Bio/MNs and P. aeruginosa PAO1 expedited the electron transfer rate and increased the generation of ·OH and O2−, consequently facilitating the efficient degradation of organic pollutants. These findings inspire Bio/MNs collaborative microorganisms for providing new methods for the green and sustainable removal of organic pollutants.

Integrated Anaerobic–Aerobic Moving Bed Biofilm Reactor and Biochar Adsorption for the Efficient Removal of Organic Matter and Nutrients from Brazilian Landfill Leachate

Landfill leachate is a complex and highly polluted wastewater that poses significant environmental challenges worldwide. This study proposes an innovative approach to addressing this challenge by developing an integrated anaerobic–aerobic moving bed biofilm reactor (MBBR) and biochar adsorption method for the efficient removal of organic matter and nutrients from landfill leachate. The MBBR provides a suitable environment for the growth of microorganisms that can degrade organic matter and nutrients, while biochar adsorption removes any remaining pollutants that are not biodegradable. The performance of this integrated system was evaluated under different operating conditions, such as the hydraulic retention time and the organic loading rate, to optimize its efficiency and sustainability. The results showed that the integrated system achieved high removal efficiencies for chemical oxygen demand (COD), ammonium–nitrogen (NH4-N), and total phosphorus (TP), with maximum removal rates of 98.5% (77% after the anaerobic–aerobic MBBR and 85.4% after biochar adsorption), 91.2% (87% after the anaerobic–aerobic MBBR and 95.9% after biochar adsorption), and 99.9% (92% after the anaerobic–aerobic MBBR and 91.7% after biochar adsorption), respectively. The proposed method offers a promising solution for the treatment of landfill leachate, which is a critical environmental issue worldwide. This study also highlights the importance of developing more effective and sustainable methods for treating landfill leachate, which can have significant impacts on public health and the environment.

Performance of a continuous micro-oxygen up-flow sludge bed reactor for assimilation of partial nitrification/anammox sludge into a CANON granular-floc system

CANON process was established in a micro-oxygen up-flow sludge bed reactor through one-step inoculation of partial nitrification/anammox sludge. The process was divided into three stages according to the influent NH+4-N concentrations. The position of aeration played a vital role as low DO concentration and sludge loss showed evident negative effects. Placing the aeration device above the sludge bed significantly enhanced the stability of the system, and the DO concentrations were maintained between 0.4 and 0.8 mg/L. The total nitrogen (TN) removal efficiency reached ∼70% within 5 days in stage I, yet the reaction stoichiometric ratios deviated from theoretical values. As the activity of anaerobic anammox bacteria (AnAOB) exceeded ammonia oxidizing bacteria (AOB) in stage III, the maximum TN removal rate reached 350 mg N/ L·d and the TN removal efficiency was retained at a relatively high value of 83%. Flocculent sludge converged into a granular-floc hybrid system with the percentage of sludge mass for particle size between 0.4 and 1 mm increased from 0% to 43.48%, and the percentage of sludge mass for particle size between 0 and 0.2 mm remained at 22.76%. Following 135 days of continuous operation, an interaction balance between AOB and AnAOB was reached with high activities and dominant abundance while nitrite oxidizing bacteria (NOB) were suppressed.

Adsorption of Methyl Orange from Water Using Chitosan Bead-like Materials.

Natural product waste treatment and the removal of harmful dyes from water by adsorption are two of the crucial environmental issues at present. Traditional adsorbents are often not capable in removing detrimental dyes from wastewater due to their hydrophilic nature and because they form strong bonds with water molecules, and therefore they remain in the dissolved state in water. Consequently, new and effective sorbents are required to reduce the cost of wastewater treatment as well as to mitigate the health problems caused by water pollution contaminants. In this study, the adsorption behaviour of methyl orange, MO, dye on chitosan bead-like materials was investigated as a function of shaking time, contact time, adsorbent dosage, initial MO concentration, temperature and solution pH. The structural and chemical properties of chitosan bead-like materials were studied using several techniques including SEM, BET, XRD and FTIR. The adsorption process of methyl orange by chitosan bead materials was well described by the Langmuir isotherm model for the uptake capacity and followed by the pseudo-second-order kinetic model to describe the rate processes. Under the optimal conditions, the maximum removal rate (98.9%) and adsorption capacity (12.46 mg/g) of chitosan bead-like materials were higher than those of other previous reports; their removal rate for methyl orange was still up to 87.2% after three regenerative cycles. Hence, this chitosan bead-like materials are very promising materials for wastewater treatment.

Rapid grinding diamond film using a grinding wheel containing nickel-plated diamond abrasives based on mechanochemical effect

The excellent properties of diamond make it a highly promising substrate material for future sensors and semiconductor devices. The surface roughness of the substrate material directly impacts the performance of the devices. Therefore, achieving efficient and low-damage processing of diamonds is crucial. However, diamond has high hardness and chemical inertness, which makes it difficult to process. To tackle the above-mentioned problem, the diamond film was ground using a grinding wheel containing nickel (Ni)-plated diamond abrasives based on the mechanochemical effect. The maximum average material removal rate of the diamond film reached 2469 nm/min under a grinding pressure of 600 N at a speed of 600 rpm, and the minimum average surface roughness of the diamond film reached 3.93 nm under 500 N 600 rpm. The rapid reaction removal of the diamond film can be attributed to the catalytic effect of the Ni plating, inducing graphitization of the diamond film at the interface contact points under the generated high temperature during friction; subsequently, it can be removed under the mechanical action of the abrasives. This work has tremendous potential for the efficient and low-damage grinding of diamond films.

Integrating biological ion exchange with biological activated carbon treatment for drinking water: A novel approach for NOM removal, trihalomethane formation potential, and biological stability

Ion exchange resins (IEX) are used in drinking water utilities to remove natural organic matter (NOM) from surface water; however, the disposal of used brine can be a major drawback. Recently, biological ion exchange (BIEX) has been proposed as an alternative to biological activated carbon (BAC) for removing natural organic matter (NOM). The present study is, to the best of our knowledge, the first attempt to use a hybrid BIEX and BAC (BIEX+BAC) system for drinking water treatment. The removal of NOM, assimilable organic carbon, and trihalomethane formation potential was investigated by operating four columns comprising IEX, BIEX, BAC, and BIEX+BAC with 18,000 bed volumes. The BIEX+BAC system was the most effective at removing dissolved organic carbon (59.9%). Based on fluorescence excitation-emission matrix spectroscopy, the BIEX+BAC column showed the maximum removal rates in all peak regions of T1, T2, and A. Using liquid chromatography-organic carbon detection, resin-containing columns were found to effectively remove humic substances, which are the principal precursors of trihalomethanes. The lowest potential for trihalomethane formation was observed in BIEX+BAC. BIEX+BAC also had the highest assimilable organic carbon removal efficiency (61.2%) followed by BIEX (52.3%), BAC (49.5%), and IEX (47.1%). The BIEX+BAC hybrid was found to be the most effective method for removing NOM fractions and reducing the formation of disinfection byproducts.

Efficient removal of Cr (VI) from wastewater using recycled polymer-based supported ionic liquid membrane technology

Hexavalent chromium (Cr (VI)) is a hazardous form of chromium that poses a significant threat to human health and the environment. Meanwhile, Polyethylene Terephthalate (PET) bottles, despite their widespread use and practicality, contribute substantially to the plastic waste problem. Converting waste PET bottles into polymeric membranes offers significant promise. Supported ionic liquid membrane (SILM) technology is a relatively new technique that shows the potential to treat contaminated water efficiently. Experimental studies have demonstrated the influence of different operating conditions on Cr (VI) separation using SILM. The key parameters include concentrations of the feed phase, carrier (Aliquat 336), and strip phase (HCl) and their interactions. Around 98% of Cr (VI) can be removed at a feed concentration of 25 mg/l, a carrier concentration of 5%, and 0.5 M of HCl as a stripping agent. The optimal carrier concentration for membrane extraction was 5% (v/v), leading to a maximum removal rate of 98.34% at optimized values. To assess the impact of carrier concentration on the membrane, SEM-EDS mapping was done. The successful wastewater treatment from such an innovative approach enables handling plastic management and water pollution.

Volatile fatty acids recovery and antibiotic degradation from erythromycin fermentation residues by combined thermal pretreatment and anaerobic fermentation: Insights into microbial communities and metabolic pathways

High resistance of erythromycin has been the key factor restricting the disposal of erythromycin fermentation residues (EFR). Considering the high sensitivity of erythromycin to acidic conditions, anaerobic fermentation may be a good approach for EFR treatment, through which pH decreases along with the volatile fatty acids (VFA) accumulation. This study firstly explored the EFR treatment by combined thermal pretreatment and anaerobic fermentation. Results showed that thermal pretreatment and anaerobic fermentation exhibited a synergistic effect on erythromycin removal. Erythromycin concentration decreased to 20.0 mg/L with the maximum removal rate of 60.0%, which was 140% and 71.4% higher than erythromycin removal by sole thermal pretreatment and anaerobic fermentation. Thermal pretreatment induced the increased VFA production by 22.3% with the highest VFA concentration of 5325.4 mg/L. Microbial analysis shows that thermal pretreatment stimulated erythromycin degradation and VFA production by increasing the microbial diversity and enriching the functional enzymes involved in acetate-producing pathways.

Permeable reactive composite approaching cathode enhanced Cr removal in soil using the byproduct of electrokinetic technology: emphasized energy utilization efficiency.

Cost-effective techniques with significant removal rates and low energy consumption are urgently required for in-situ Cr-contaminated soil remediation to reduce potential environmental toxicity to the ecosystem and human bodies. Electrokinetic technology is a valuable and promising soil remediation technology; however, the acidic and alkaline fronts evolutioninduced by the electrokinetic byproducts (H+, OH-) has significant hindering characteristics for ion removal. To effectively utilize the byproducts for enhancing Cr elimination, this paper proposed the permeable reactive composite approaching cathode with rhamnolipid-modified biochar as reactive material. Power utilization efficiency (η) was presented to comprehensively evaluate the target species elimination effect, considering removal rate and energy consumption. Results suggested that biosurfactant rhamnolipid stimulated Cr removal in acid and base fronts. Acid front induced rhamnolipid protonation reducing anolyte Cr(VI) to Cr(III), and base front induced rhamnolipid deprotonation complexing with Cr(III) and expediting Cr(VI) dissolution by electrostatic repulsion. Permeable reactive composite approaching cathode induced the maximum removal rate of Cr(VI) and Cr(III) in each section by impelling the alkaline front. Approaching cathode caused increased resistance and energy consumption in the near-anode regions, ultimately decreasing energy utilization efficiency. Optimized moving frequency and applied potential magnitude could adjust power consumption distribution in a single soil layer to obtain better electrokinetic removal performance of contaminates. This work provided essential scientific and practical importance for in-situ electrokinetic remediation of Cr(VI) and Cr(III), considering elimination efficiency and energy consumption in the future.

Characterization of the Nitrogen Removal Potential of Two Newly Isolated Acinetobacter Strains under Low Temperature

Excess nitrogen and phosphorus in the water causes several ecological problems for nutrients. Biological nitrogen removal is an economical and efficient way to prevent excessive nitrogen in the environment. For most areas of China, temperatures are usually lower than 20 °C except during the summertime. It is necessary to discover microbes that can efficiently remove nitrogen at low temperatures. In this study, two Acinetobacter strains were isolated from a sample in a wastewater tank in Taizhou for their capabilities to remove NO3−–N and NO2−–N at 15 °C. Heterotrophic nitrification experiments showed that both strains could efficiently remove nitrogen from the culture medium. The maximum removal rates of NH4+–N were 3.15 mg/L·h and 4.74 mg/L·h for heterotrophic nitrification by the strains F and H, respectively. Strain H grew faster and removed both nitrite and nitrate more efficiently than strain F. Genome sequencing showed that strains F and H could be classified into Acinetobacter johnsonii and Acinetobacter bereziniae, respectively. NO2−–N (100 mg/L) was completely removed in 3 days by strain H. The maximum NO3−–N removal rate was 3.53 mg/L·h for strain F. When strain H was cultured in a broth with 200 mg/L NO3−–N, 97.46% of NH4+–N (200 mg/L) was removed in 5 days, and the maximum NH4+–N removal rate was 4.04 mg/L·h. Genomic sequence analysis showed that both the strains lacked genes involved in the denitrification pathway that transforms NO3− into N2. This implies that nitrate or nitrite is removed through the nitrogen assimilation pathway. Genes responsible for nitrate assimilation are clustered together with molybdopterin cofactor biosynthesis genes. Strain H contains fewer resistance genes and transfer elements. All the above data demonstrate that strain H is a promising candidate for nitrogen removal at lower temperatures. But there is still a lot to be done to systematically evaluate the potential of A. bereziniae strain H in treating wastewater at a pilot scale. These include the long-term performance, environmental tolerance, and nitrogen removal efficiency in wastewater. And the application of these Acinetobacter strains in diverse wastewater treatment settings might require careful optimization and real-time monitoring.

Non-immersed zigzag microalgae biofilm overcoming high turbidity and ammonia of wastewater for muti-pollutants bio-purification

Biological treatment that utilizes microalgae technology has demonstrated outstanding efficacy in the wastewater purification and nutrients recovery. However, the high turbidity of the digested piggery wastewater (DPW) leads to serious light attenuation and the culture mode of suspended microalgae results in a huge landing area. Thus, to overcome light attenuation in DPW, a non-immersed titled zigzag microalgae biofilm was constructed by attaching it onto a porous cotton cloth. As a result, the light could directly irradiate microalgae biofilm that attached on both sides of the cotton cloth, and the microalgal biofilm area was up to 6 m2 per bioreactor landing area. When the non-immersed zigzag microalgae biofilm bioreactor (N-Z-MBP) was used to treat wastewater with an ammonia nitrogen (NH4+-N) concentration of 362 mg L−1, the NH4+-N was completely removed in just 5 days and the maximum growth rate of microalgae biofilm reached 7.02 g m−2 d−1. After 21 days of long-term sequencing batch operation for the N-Z-MBP, the biomass density of the biofilm reached 52 g m−2 and remained at this high value for the next 14 days. Most importantly, during the 35 days’ running, the NH4+ -N maximum removal rate of single batch reached up to 65 mg L−1 d−1 and its concentration in the effluent was always below the discharge standard value (80 mg L−1 form GB18596–2001 of China) and total phosphorus was completely removed in each batch. Furthermore, the biomass concentration of microalgae cells in the effluent of the N-Z-MBP was almost zero, indicating that the non-submerged biofilm achieved in situ separation of microalgae from the wastewater. This work suggests that the N-Z-MBP can effectively purify DPW over a long period, providing a possible strategy to treat wastewater with high ammonia nitrogen and high turbidity.

Nitrogen removal performance and bacterial flora analysis of a nitrification‑sulphur autotrophic denitrification coupled with permeable reaction wall (NSAD+PRW) treating rare earth mine groundwater

Rare earth elements (REEs) are strategic resources for the development of modern society. However, their mining can cause nitrogen pollution in groundwater. In this study, a nitrification-sulphur autotrophic denitrification-enhanced permeable reaction wall (NSAD+PRW) was constructed to treat groundwater in rare earth mines and the feasibility of its engineering application was demonstrated. The results show that a maximum removal rate of 100 % was achieved for NO3−-N. The average removal content of NH4+-N was 27.15 mg/L and the highest TN removal content of total nitrogen (TN) reached 145.49 mg/L. The removal rates of most REEs exceeded 99.88 %. The composite filler provides a good environment for microorganisms, which also produce extracellular polymeric substances (EPS) to protect themselves during nitrogen removal. In addition, some nitrifying bacteria (Rhodanobacter and Nitrospira) and denitrifying bacteria (Thiobacillus, Sulfurovum, and Ferritrophicum) with high adaptability to rare earth mine groundwater were found. In conclusion, the results of this study provide an important reference for nitrogen removal from groundwater in rare earth mines with high engineering application significance.

Degradation mechanism of saliferous compounding heavy metals-organic wastewater by manganese and iron cycling in the microbial fuel cell

With the rapid development of industry and agriculture, the heavy metal ions and organic matter pollution coexistence systems become increasingly common, aggravating environmental damage and endangering water safety. Therefore, an urgent need to find a general method to achieve the typical removal of two pollutants or promote the removal of one to improve another degradation, solving the related pollution problems. Meanwhile, the related research microorganism’s salt and heavy metal tolerance is lower, limiting the related research. Therefore, the study makes the deep-sea sediment as the strain source, obtaining the low-valence manganese-oxidizing functional bacteria (OMF) with salt-tolerant and heavy metal-tolerant characteristics, constructing the closed-circuit microbial fuel cell (MFC), carried out the degradation mechanism of saliferous compounding heavy metals-organic wastewater by manganese and iron cycling processes. The results showed that under the salt content conditions of 3%, pH = 6, external resistance of 510 Ω, Mn2+ concentration of 11 g/L, Mn2+:Fe2+ = 1:0.3 and OMF (Rhodococcus erythropolis: Microbacterium kitamiense: Dietzia = 1:2:1) inoculation amount of 20%. The maximum removal rates of organic pollutants (400 mg/L), Cu2+ (250 mg/L), Co2+ (150 mg/L) and Ni2+ (200 mg/L) were 94.72%, 91.23%, 99.89% and 99.97%, respectively. Realizing the heavy metal ions and organic matter pollution coexisting systems purification. The manganese-iron cycle mediated by oxidized low-valent manganese functional bacteria has a dual effect on the pollutant’s degradation process through MFC. Firstly, the synergistic redox cycle transformation of iron and manganese promoted the production of OH and accelerated the degradation of organic matter. Secondly, the ferromanganese oxidation products and bio-nanowires enhance material oxidation and electron transfer, improving the organic pollution oxidation and heavy metal ions fixation efficiency. This study provides a new idea for the heavy metal ions and organic matter pollution coexisting systems remediation and MFC degradation efficiency optimization.

Efficient Treatment of Antibiotic Cefalexin Sludge by Wet Oxidation: an Experimental and Theoretical Study

In the present study, wet oxidation of antibiotic cefalexin sludge from pharmaceutical wastewater treatment was investigated. The experiments were carried out in a stainless-steel batch autoclave reactor. The results show that the maximum removal rate of volatile suspended solids (VSS) can reach 91.3% at 260 °C within 60 min with an initial oxygen pressure of 1.0 MPa. Simultaneously, the chemical oxygen demand (COD) removal rate of 64.1% was reached. The antibiotic cefalexin was totally eliminated under wet oxidation conditions. DFT calculation was performed to illustrate the initial reaction pathway. The energy diagram proposed initial thermal hydrolysis pathway of cefalexin. These results indicated that wet oxidation provided a promising treatment method for the antibiotic cefalexin sludge, which can be used for the efficient removal of cefalexin.

Gas stripping coupled with in-situ oxidation assisted microwave remediation of contaminated soil for efficient removal of polycyclic aromatic hydrocarbons (PAHs)

Thermal desorption technology at low temperatures has been extensively researched. However, the challenge remains in maintaining soil ecological function while effectively removing PAHs from contaminated soil using this method. Based on the gas hammer fragmentation concept, this study presents the strategy of gas stripping (steam extraction) coupled with microwave remediation. A multifunctional bluecoke-based modifier (MnO2/KHCO3@BC) was prepared followed by an investigation on the removal effect, soil characteristics and remediation mechanism of MnO2/KHCO3@BC-assisted microwave remediation of pyrene (PAHs model) contaminated soil. The research findings indicate that MnO2/KHCO3@BC is more effective in generating oxygen vacancies, facilitating surface electron transfer, and enhancing the oxidation effect of ROS on pyrene compared to KHCO3@BC and MnO2@BC. Despite having slightly inferior electromagnetic properties to BC, MnO2/KHCO3@BC could achieve a microwave remediation temperature of approximately 300 °C under optimal experimental conditions. MnO2/KHCO3@BC demonstrated remarkable pyrene removal efficiency with a maximum removal rate of 98.34%, making it an ideal candidate for pyrene remediation. Moreover, the remediated soil exhibited a weakly acidic nature, with a significant decrease in particle size and a substantial increase in potassium content. The study also highlighted a novel synergistic mechanism of ''microwave heating - gas stripping - oxidation,'' which can efficiently remove most of the pyrene adsorbed inside and outside of soil particles and degrade it into low-toxic and small-molecule organic matter, CO2, and H2O. Overall, the findings of this study could hold potential significance for upcoming endeavours concerning polluted industrial areas.

Modi-Red Mud Loaded CoCatalyst Activated Persulfate Degradation of Ofloxacin

As an abundant potentially dangerous waste, red mud (RM) requires a straightforward method of resource management. In this paper, an RM catalyst loaded with cobalt (Co-RM) was prepared by the coprecipitation method for the efficient activation of persulfate (PS). Its degradation performance and mechanism of ofloxacin (OFL) were investigated. The characterization results of scanning electron microscopy, X-ray diffractometer, and energy dispersive spectrometer showed cobalt was successfully loaded onto the surface of RM, and the catalyst produced could effectively activate PS. Under the conditions of 15 mg/L OFL, 0.4 g/L Co-RM, 4 g/L PDS, 3.0 pH, and 40 °C temperature, the maximum removal rate of OFL by the Co-RM/PDS system was 80.06%. Free radical scavenging experiments confirmed sulfate radicals were the main active substances in the reaction system. The intermediates in OFL degradation were further identified by gas chromatography-mass spectrometry, and a possible degradation pathway was proposed. Finally, the relationship between defluorination rate and time in the Co-RM/PDS degradation OFL system was described by the first-order kinetic equation. This work reports an economical, environmental solution to the use of waste RM and provides a research basis for the further exploration of RM-based catalysts.