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Exploration of easily produced visible light photocatalysts is still necessary. Thus, this study investigated the catalytic performance of a mixed metal oxide-titanium dioxide (MMO-TiO2) to remove perfluorooctanoic acid (PFOA), a typical and harmful perfluoroalkyl substance, under visible light conditions. Analysis of degradation efficiencies revealed that MMO-TiO2 exhibited a remarkable removal efficiency of 95.99 ± 1.49 %, surpassing other catalysts, including TiO2, ZnAl, MMO, and ZnAl-TiO2. MMO-TiO2, derived from ZnAl-TiO2 calcination, displayed a 5.66-fold higher apparent degradation rate constant (1.07 × 10−2 min−1) compared to ZnAl-TiO2 (1.89 × 10−3 min−1). These materials were characterized via X-ray powder diffractometry, Fourier transform infrared-attenuated total reflectance, N2 adsorption-desorption analysis, and field emission-scanning electron microscopy. Results revealed that O2•- radicals play a pivotal role as the predominant species that mediate PFOA removal. Comparative experiments using probe compounds confirmed increased O2•- production during MMO-TiO2 photoreaction under visible light. In addition, this study explored the effect of operational parameters, such as catalyst dose, initial PFOA concentration, solution pH, and water matrices on the photocatalytic removal process. These findings provide insight into the removal of PFOA using MMO-TiO2, highlighting the potential of this visible light catalyst for the eco-friendly removal of persistent organic pollutants in aquatic systems.

Objectives This study aimed to monitor ammonia volatilization in upland fields under different nitrogen fertilizer applications, comparing compost manure (CM) and composite fertilizer (CF) and investigate the environmental factors influencing ammonia volatilization. Methods Ammonia was collected using the static chamber method in upland fields, and the soil analyses were conducted before and after ammonia volatilization monitoring. Pearson's correlation analysis and machine learning were utilized to determine the relationship between ammonia volatilization and environmental factors. Growth characteristics of harvested crops were analyzed, and Duncan analysis confirmed significant differences between nitrogen fertilizer treatments. Results and Discussion In both CM and CF fertilized fields, there was no significant difference in ammonia volatilization. However, more ammonia volatilization was observed in the potato field compared to the Chinese cabbage field, attributed to higher NH4+-N content in the soil of the potato field. Machine learning identified soil temperature and moisture as significant factors affecting ammonia volatilization. The analysis of crop growth revealed a positive effect of increased nitrogen fertilizer application. The result showed that single CM application was insufficient to meet crop nutrient demands. Conclusion This study quantified ammonia emissions, identified influencing factors, and provided valuable data for enhancing fertilizer use efficiency and nitrogen management strategies in agriculture.

In a photocatalytic Cr(VI) reduction system, a hole scavenger (electron donor) is required to enhance the performance of photocatalytic reaction. In this study, mandarin peel extract (ME) was used as a natural sacrificing agent to enhance the photocatalytic Cr(VI) removal performance. The use of ME increased the Cr(VI) reduction rate (0.0286 min−1), and a Cr(VI) removal efficiency of 99.1% was achieved within 150 min. Hole scavenging by antioxidants contained in ME on TiO2 surface contributed to the enhancement of the photocatalytic Cr(VI) removal. Under the optimal conditions (ME volume = 5 mL, TiO2 dose = 0.2 g L−1, and pH = 2), the Cr(VI) reduction rate constant was about 1.2–7.3 times higher than the values reported in the literature. Furthermore, experiments on Cr(VI) treatment in real wastewater and H2O2 production showed the suitability of ME for other reaction systems. The photocatalytic Cr(VI) reduction efficiency achieved in 150 min in real wastewater increased from 58.6% to 83.6% after ME addition. This study employed a waste material as a reagent to improve the photocatalytic Cr(VI) removal performance for the photoreduction of a water pollutant, namely Cr(VI), which can be employed as a strategy for simultaneous waste and water treatment.

Objectives In this study, thermo-chemically treated carcasses from livestock burial sites were composted, and kenaf and rice straw were used as moisture control agents for composting. Changes in the characteristics of the compost pile for 60 days were observed, and the physico-chemical characteristics of the comopost were analyzed after the end of the experiment to evaluate the potential for recycling of buried livestock carcasses through composting. Methods The compost pile was prepared by mixing the treated carcass with kenaf and rice straw in the ratios of 7:3, 6:4, 2:1, and 1:1 (V/V), respectively. Samples were collected on days 0, 7, 15, 30, 45, and 60 after deposition to analyze temperature, pH, and EC. The emissions of the three gases H2S, NH3 and CO2 generated were measured. After composting was completed, the characteristics of the compost pile were identified through physicochemical analysis. Results and Discussion After the initial mixing of raw materials, the temperature increased in all treatment areas after the initial stage. The initial pH of composting was strongly alkaline, then gradually decreased and stabilized on the 50th day of composting. H2S and NH3 are mainly generated in the early composting stage and decreased rapidly. CO2 reached its maximum concentration on day 15 and then decreased. After the end of composting, the nitrogen, phosphorus, and potassium contents increased compared to before composting. In all compost piles, the organic matter content was over 30%, the moisture content was 4.3~5.9%, and the organic matter to nitrogen ratio was 65.3~82.9. Escherichia coli and Salmonella were not detected in all compost piles. The maturity of compost piles in which carcass and Kenaf were mixed in the ratio of 2:1 and the compost bed in which carcass and rice straw were mixed in the ratio of 6:4 and 1:1 were over 70, showing acceptable maturity. Conclusion In this study, the recycling potential of livestock burial samples through composting was evaluated. Physico-chemical analysis has shown that kenaf or rice straw and carcass are to be mixed to form a compost pile that can be used as compost.

Objectives Major factors affecting ammonia emission from the soil and strategies to reduce ammonia emission were investigated through literature surveys. Methods An academic search was conducted using keywords such as agriculture, ammonia, and fine dust, and the effects of soil characteristics on ammonia emission were summarized for each factor. Results and Discussion Emissions of ammonia into the atmosphere can reduce economic returns for a farmer and negatively impact the atmospheric environment by acting as a precursor to PM2.5 formations. It is reported that agriculture accounts for 78% of the total ammonia emission sources in Korea. Ammonia emission from the soil is affected by the type of ammonia fertilizer, soil moisture, pH, temperature, cation exchange capacity, organic matter, and soil texture. An increase in soil moisture increases ammonia emissions. As soil pH increases, ammonia emissions increase, noticeably above 7.5. An increase in soil temperature increases the rate of hydrolysis of urea and the rate of conversion to ammonia gas, resulting in increased ammonia emissions. Soils with high cation exchange capacity adsorb ammonium to reduce ammonia emissions. Soils with a high clay content and soil organic matter content are more buffered to changes in soil pH, reducing ammonia emissions. Conclusion Based on understanding the mechanisms and causes of ammonia emission from the soil, it is possible to establish soil and environmental management to reduce ammonia emissions into the atmosphere.

Material science is an interdisciplinary research field that includes interrelationships between the composition, structure, process, and performance of various materials and is widely integrated with other disciplines to form many interdisciplinary subjects [...]

Bioleaching has been regarded as a green alternative to chemical leaching in metal extraction processes. In this study, the bioleaching properties of indigenous acidophilic bacteria for various sulfide minerals were compared and evaluated in terms of pH reduction and metal leaching. The primary minerals in the samples were sphalerite (ZnS) (SP), galena (PbS) (GN1 and GN2), pyrite (FeS2) (PY), and chalcopyrite (CuFeS2) (CCP), and an indigenous acidophilic bacterium, Acidiphilium cryptum (99.56%), was applied for bioleaching experiments. The metal extraction in bioleaching differed according to the mineral content. The leached metal concentration of Zn was higher than that of Pb for the SP sample with a high ZnS content, whereas the concentration of Pb was higher than that of Zn for the GN1 and GN2 samples with a high PbS content. Meanwhile, the leaching rate of Zn was faster than that of Pb for all samples. Corrosion action was observed on the surface of bacterial residues in SP and GN1 samples. These results show that the bioleaching mechanism based on sulfide minerals proceeds through indirect biological oxidation, chemical oxidation, and direct bacterial oxidation. The results of this study can provide basic research data for process optimization when employing bioleaching to extract valuable metals.

Oxytetracycline (OTC) is a tetracycline antibiotic that is widely used in the drug therapy and livestock industry and may threaten human health and ecosystems when released into the environment. In this study, a catalyst was prepared from hand-warmer waste using a simple magnetic separation method. The prepared hand-warmer waste catalyst (HWWC) was used as a persulfate (PS) activator for OTC removal. Characterization methods, such as X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectrometry, were used to investigate the crystal structure, surface morphology, and weight ratios of the elements in the HWWC. The degradation efficiency of OTC in the presence of the catalyst and PS was studied, and the radical generation mechanism of the catalyst was investigated. The removal ratio of OTC by PS activation was greater than 99% for a reaction time of 24 min at a pH of 6. The effects of the HWWC dosage, PS concentration, and solution pH on OTC degradation were also investigated. The reuse test revealed that HWWC can be reused for eight cycles with great stability. These results suggest that PS activation using hand-warmer waste can be an efficient strategy for the degradation of antibiotics.

This study assessed the applicability of Fe-impregnated biochar derived from cattle manure (Fe-CMB) as an adsorbent for removing Sb(V) from aqueous solutions and investigated the Sb(V) adsorption mechanism. Fe-CMB was mainly composed of C, O, Cl, Fe, Ca, and P, and the adsorption of Sb(V) onto Fe-CMB was identified using an energy dispersive spectrometer and Fourier transform infrared spectroscopy. Sb(V) adsorption reached equilibrium within 6 h, and the Sb(V) adsorption data as a function of time were well described by the pseudo-second-order model. The Langmuir isotherm model fit the equilibrium data better than the Freundlich model. The maximum adsorption capacity of Fe-CMB for Sb(V) obtained from the Langmuir model was 58.3 mg/g. Thermodynamic analysis of Sb(V) adsorption by Fe-CMB indicated that the adsorption process was exothermic and spontaneous. The Sb(V) removal percentage increased with the Fe-CMB dose, which achieved a removal of 98.5% at 10.0 g/L Fe-CMB. Increasing the solution pH from 3 to 11 slightly reduced Sb(V) adsorption by 6.5%. The inhibitory effect of anions on Sb(V) adsorption followed the order: Cl− ≈ NO3− < SO42− < HCO3− < PO43−.

This study investigated the applicability of algae (Hizikia fusiformis, Green gracilaria, and Codium fragile) for removing heavy metals (Cd2+, Cu2+, Ni2+, and Pb2+) from aqueous solutions. Among the algae, H. fusiformis was chosen as a bioadsorbent and modified with NaOH and HCl. The results showed that the biosorption capacity of H. fusiformis improved significantly after treatment with NaOH; however, H. fusiformis modified with HCl did not achieve the expected value. The NaOH treatment enhanced the biosorption of metals on the treated H. fusiformis because of the hydrolysis reaction producing carboxylic (–COOH) and hydroxyl groups (–OH). The kinetics for Cd2+, Cu2+, Ni2+, and Pb2+ biosorption well fitted to pseudo-first-order, pseudo-second-order, and Elovich models, with R2 of >0.994. The Freundlich model provided a good fit for the equilibrium biosorption of Cd2+, Cu2+, and Ni2+ by both algae and the Langmuir model for Pb2+. The maximum biosorption of metals was in the order Pb2+ >> Cu2+ ≈ Ni2+ > Cd2+, with qmax of 167.73, 45.09, 44.38, and 42.08 mg/g, respectively. With an increase in the solution pH, metal biosorption was enhanced, and considerable enhancement was observed in the pH range of 2–4. Thus, H. fusiformis is expected to be considered a superior candidate for metal biosorption.

A mechanized thermo-chemical treatment system was developed to treat the undecomposed carcass and remediate livestock burial sites. Animal carcasses were thus processed via crushing, mixing, and treatment with quicklime treatment, heat treatment (200–500 °C), and mixing with sawdust. The machinery was applied to two sites where 16,000 chickens and 418 pigs had previously been buried in fiber-reinforced plastic storage bins. No dioxins were detected in the gas discharged during processing, and the concentration of total volatile organic compound, toluene, ethylbenzene, xylene, and styrene were 430.3, 139.0, 18.3, 21.4, and 10.4 μg/m3, respectively, which were below the air pollutant emission standards issued by the Korean Ministry of Environment. Korean standards stipulating the use of treated carcasses as compost (C, N, and P content, heavy metal concentration, Escherichia coli, and Salmonella) were met, but the germination index value was less than 70, not satisfying the criteria. Plant height, leaf length, leaf width, and dry weight of lettuce grown in soil amended with treated carcass product were significantly lower than those grown in low nutrient soil due to the poor germination index of the treated carcass. These results indicate that a composting process is required before the use of the treated carcass as a fertilizer. The addition of zeolite retarded the elution of ammonia from the carcasses and its efficiency was about 87.9%. It is expected that the mechanized thermo-chemical treatment process developed in this study could replace other technologies for the remediation of livestock burial sites.

The objectives in this study are to improve the performance of PVDF membrane by incorporating TiO2 and silane at various dosages and optimize fabricating conditions by using response surface methodology (RSM) for membrane distillation (MD) application. The PVDF membrane was synthesized by phase inversion method using various TiO2, silane and polymer concentrations. Membranes were characterized by performing contact angle measurements, SEM and FTIR observations. Ammonia rejection and permeate flux were measured by operating a direct contact distillation module treating ammonium chloride solution. A PVDF membrane created by adding TiO2 modified by silane improved membrane hydrophobicity. However, the effect of silane on membrane hydrophobicity was less pronounced at higher TiO2 concentrations. Highest ammonium rejection was associated with the highest membrane hydrophobicity. RSM analysis showed that fabricating conditions to achieve highest flux (10.10 L/m2·h) and ammonium rejection (100.0%) could be obtained at 31.3% silane, 2.50% TiO2, and 15.48% polymer concentrations. With a PVDF-TiO2 composite membrane for MD application, the effect of TiO2 was dependent upon silane concentration. Increasing silane concentration improved membrane hydrophobicity and ammonium rejection. RSM analysis was found to bea useful way to explore optimum fabricating conditions of membranes for the permeate flux and ammonium rejection in MD.

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to achieve extended photoresponse to visible light and increased photocatalytic efficiency. In this study, we report the synthesis of a PANI/TiO2 composite with different weight ratios of PANI, which was subsequently employed for photocatalytic degradation of methylene blue (MB), bisphenol A (BPA), and bacteriophage MS2 under visible-light irradiation. The functional groups, morphology, and light response of the composite were characterized by Fourier-transform infrared spectroscopy, field-emission transmission electron microscopy, and diffuse reflectance UV–visible spectroscopy, respectively. The PANI/TiO2 composite containing 4% by weight ratio of PANI was most suitable for MB degradation, and this photocatalyst was very stable even after repeated use (four cycles). The degradation of BPA and bacteriophage MS2 by PANI/TiO2 composite reached 80% in 360 min and 96.2% in 120 min, respectively, under visible-light irradiation. Therefore, the PANI/TiO2 composite with enhanced visible-light photocatalytic efficiency and stability can be widely used for the degradation of water contaminants.

We assessed the applicability of rice husk (RH) to remove cationic dyes, i.e., methylene blue (MB) and crystal violet (CV), from water. RH thermally treated at 75 °C showed a higher adsorption capacity than that at high temperatures (300–700 °C). For a suitable CV-adsorption model, a pseudo-first-order model for MB adsorption was followed by the kinetics adsorption process; however, a pseudo-second-order model was then suggested. In the qt versus t1/2 plot, the MB line passed through the origin, but that of CV did not. The Langmuir isotherm model was better than the Freundlich model for both dye adsorptions; furthermore, the adsorption capacity for MB and CV was 24.48 mg/g and 25.46 mg/g, respectively. Thermodynamically, the adsorption of both MB and CV onto the RH was found to be spontaneous and endothermic. This adsorption increased insignificantly on increasing the solution pH from 4 to 10. With an increasing dosage of the RH, there was an increase in the removal percentages of MB and CV; however, adsorption capacity per unit mass of the RH was observed to decrease. Therefore, we conclude that utilizing RH as an available and affordable adsorbent is feasible to remove MB and CV from wastewater.

Ceramic membranes and ion exchangers are effective at removing turbidity and ionic contaminants from water, respectively. In this study, we demonstrate the performance of a hybrid ion-exchange fabric/ceramic membrane system to treat metal ions and turbidity at the same time in synthetic wastewater. The removal rate of As(V) and Zn(II) by the ceramic membrane increased with solution pH, while turbidity was completely removed regardless of the solution pH. The main reaction of As(V) removal was adsorption at solution pH 6 and precipitation at solution pH 8, whereas phase-change was the predominant reaction for Zn(II) removal at both solution pH values. The removal efficiency of the ion-exchange fabric was affected by the solution pH, with the maximum removal capacity of As(V) occurring at solution pH 4. The As(V) adsorption capacity of the ion-exchange fabric reached equilibrium within 120 min. The ion-exchange capacity of the ion-exchange fabric was compared with commercial ion-exchange fibers. The regeneration efficiency of the ion-exchange fabric using 0.1 M NaCl solution was around 95% on average and decreased slightly as the number of regeneration cycles was increased. Over 80% of As(V) and Zn(II) were steadily removed at solution pH 6 by the hybrid ion-exchange fabric/ceramic membrane system. Reduced flow rate and removal capacity were recovered through a backwashing process during continuous treatment with the hybrid ion-exchange fabric/ceramic membrane system.

In this study, we explored the adsorption potential of biochar derived from palm kernel shell (BC-PKS) as an affordable adsorbent for the removal of crystal violet from wastewater. Kinetics, equilibrium, and thermodynamics studies were carried out to evaluate the adsorption of crystal violet onto BC-PKS. The kinetics adsorption process followed the pseudo-second-order model, indicating that the rate of adsorption is principally controlled by chemisorption. The adsorption equilibrium data were better fitted by the Langmuir isotherm model with a determination coefficient of 0.954 and a maximum adsorption of 24.45 mg/g. Thermodynamics studies found the adsorption of crystal violet by BC-PKS to be endothermic with increasing randomness at the BC-PKS/crystal violet interface. The percentage removal and adsorption capacity increased with the pH of the solution, as the negative charges on the biochar surface at high pH enhance the electrostatic attraction between crystal violet molecules and BC-PKS. Increasing the BC-PKS dosage from 0.1 to 1.0 g increased percent removal and decreased the adsorption capacity of crystal violet onto BC-PKS. Therefore, biochar from agricultural by-products, i.e., palm kernel shell, can be cost-effective adsorbents for the removal of crystal violet from textile wastewater.

Polyacrylonitrile (PAN) fibers were prepared via electrospinning and were modified with diethylenetriamine (DETA) to fabricate surface-modified PAN fibers. The surface-modified PAN fibers were used to evaluate their adsorption capacity for the removal of Cu(II) from aqueous solutions. Batch adsorption experiments were performed to examine the effects of the modification process, initial concentration, initial pH, and adsorbent dose on the adsorption of Cu(II). Kinetic analysis revealed that the experimental data fitted the pseudo-second-order kinetic model better than the pseudo-first-order model. Adsorption equilibrium studies were conducted using the Freundlich and Langmuir isotherm models, and the findings indicated that the PAN fibers modified with 85% DETA presented the highest adsorption capacity for Cu(II) of all analyzed samples. Moreover, the results revealed that the Freundlich model was more appropriate than the Langmuir one for describing the adsorption of Cu(II) onto the modified fibers at various initial Cu(II) concentrations. The maximum adsorption capacity was determined to be 87.77 mg/g at pH 4, and the percent removal of Cu(II) increased as the amount of adsorbent increased. Furthermore, the surface-modified PAN fibers could be easily regenerated using NaOH solution. Therefore, surface-modified PAN fibers could be used as adsorbents for the removal of Cu(II) from aqueous solutions.

UV/H2O2 is a commonly used advanced oxidation process for removing non-biodegradable organic compounds. However, additional efforts are needed to understand the relative significance of operational factors during the UV/H2O2. Here, we investigated the effect and specific contribution of crucial factors such as H2O2 concentration, UV intensity, and reaction time on the color and total organic carbon (TOC) removal efficiency in textile wastewater using the one-factor-at-a-time method and multi-layer perceptron (MLP) analysis. The results showed that color removal was enhanced with high H2O2 concentration, high UV intensity, and long reaction time. Overall, more than 99% removal of color was achieved by the UV/H2O2, utilizing the following parameters: H2O2 concentration of 5 mM, UV intensity of 26.6 W/m², and reaction time of 180 min. On the other hand, the removal of TOC was increased by high H2O2 concentration and long reaction time, but not by high UV intensity. In the MLP analysis, the H2O2 concentration was identified as the primary factor affecting both color and TOC removal, accounting for 43% and 50% reduction of the color and TOC, respectively. Overall, this study helps to understand the relative importance of the most critical operating factors in treating actual textile wastewater by the UV/H2O2. [ABSTRACT FROM AUTHOR]