In this study, activated carbon in the form of carbonaceous hydrochar adsorbents with highly functionalized surface-active sites were produced from coffee husk waste via hydrothermal carbonization ...under low-temperature conditions (180 °C) and subsequent chemical activation. Thereafter, the hydrochars were characterized using diverse analytical techniques, and batch experiments of methylene blue (MB) adsorption were performed under various operating conditions. The results indicated that the activated hydrochar (AH) had a larger specific surface area (862.2 m2 g−1) compared to that of its carbonaceous precursor (33.7 m2 g−1). The maximum MB sorption capacity of the hydrochar activated with potassium hydroxide was extremely high (415.8 mg g−1 at 30 °C). In addition, adsorption isotherms and kinetics were studied using experimental data fitting to further understand and describe the dynamic equilibrium, dynamic kinetics, and mechanism of MB adsorption onto the prepared hydrochars. As compared to the Freundlich isotherm model, the Langmuir isotherm model provided a better fit with the experimental data exhibiting a maximum monolayer adsorption capacity of 418.78 mg g−1. The linear pseudo-second-order kinetic model was found to be suitable for describing the adsorptive kinetics of the hydrochar. The results demonstrated the immense potential of coffee husk waste to produce activated carbon as an alternative green hydrochar that can be applied to dye removal from wastewater as well as improvement of waste management.
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•High-performance activated hydrochar (AH) was derived from coffee husks and tested.•AH had an excellent specific surface area of 862.2 m2 g−1.•Derived AH efficiently removed methylene blue (MB) dye.•The highest MB removal (415.8 mg g−1) was achieved under experimental conditions.•Adsorption isotherm and kinetic studies were conducted by experimental data fitting.
•Antibacterial ZnO nanoparticles for edible surface coatings were successfully fabricated.•Incorporation of ZnO nanoparticles in a chitosan/gum arabic edible coating was evaluated.•Effects of ZnO ...nanoparticles on the performance of the edible coating for banana preservation were investigated.•Properties of the edible coating and changes in the physical chemical properties of the banana were investigated.•The developed edible coating composite can be applied for banana preservation.
ZnO nanoparticles are nontoxic inorganic oxides that have been extensively used as a supplement for zinc nutrients and antibacterial agents in the food industry, especially in edible coatings to protect food from deterioration by viruses, fungi, and bacteria. In this work, ZnO nanoparticles were fabricated by a hydrothermal method and characterized by scanning electron microscopy and X-ray diffraction. The prepared ZnO nanoparticles exhibited good antibacterial properties against several bacteria, including Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. The ZnO nanoparticles as an antibacterial agent were incorporated into a chitosan/gum arabic (CH/GA) edible coating, and the protective performance for the preservation of bananas was investigated. The obtained CH/GA/ZnO coating significantly improved the quality and shelf life of bananas at a temperature of 35 °C and relative humidity (RH) of 54 %. The banana surface treated with the CH/GA/ZnO coating was relatively smooth with a CH/GA/ZnO film thickness of approximately 50 μm. The utilization of the resultant coating enabled the maintenance of banana quality, including fruit firmness, weight loss, reducing sugar, and titratable acidity, for a remarkably longer period. The banana coated with the CH/GA/ZnO system was demonstrated to maintain freshness for more than 17 d in comparison with the less than 13 d for the control banana at 35 °C and 54 % RH.
This study investigated methyl orange (MO) dye adsorption using three biochars produced from agro-waste and invasive plants; the latter consisted of wattle bark (BA), mimosa (BM), and coffee husks ...(BC). BC had the lowest specific surface area (2.62 m2/g) compared to BA (393.15 m2/g) and BM (285.53 m2/g). The adsorption efficiency of MO was stable at pH 2–7 (95%–96%), whilst it had reduced stability at pH 7–12. Between 0 and 30 min, MO adsorption efficiency was >82%, and at 120 min, representative adsorption equilibrium had occurred. The maximum adsorption capacity of the biochars was 12.3 mg/g. The underlying adsorption mechanisms of the three biochars were governed by electrostatic adsorption and pore diffusion. There was an abundance of active sites for adsorption in BA and BM, while chemical adsorption appeared to be more vital for BC, as it contained more functional groups on its surface. The highest MO adsorption efficiency occurred with BM. BC was not recommended for MO removal, as it was observed to stain the water when a dose exceeding 5.0 g/L was utilized.
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•Biochars were successfully derived from agro-waste and invasive plants.•After only 30 min the methyl orange adsorption efficiency on biochar was more than 82%.•The adsorption equilibrium was established at 120 min.•The highest adsorption occurred with biochar from mimosa.
The quest for finding an effective photocatalyst for environmental remediation and treatment strategies is attracting considerable attentions from scientists. In this study, a new hybrid material, ...Cu0.5Mg0.5Fe2O4–TiO2, was designed and fabricated using coprecipitation and sol-gel approaches for degrading organic dyes in wastewater. The prepared hybrid materials were fully characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results revealed that the Cu0.5Mg0.5Fe2O4–TiO2 hybrid material was successfully synthesized with average particle sizes of 40.09 nm for TiO2 and 27.9 nm for Cu0.5Mg0.5Fe2O4. As the calculated bandgap energy of the hybrid material was approximately 2.86 eV, it could harvest photon energy in the visible region. Results indicate that the Cu0.5Mg0.5Fe2O4–TiO2 also had reasonable magnetic properties with a saturation magnetization value of 11.2 emu/g, which is a level of making easy separation from the solution by an external magnet. The resultant Cu0.5Mg0.5Fe2O4–TiO2 hybrid material revealed better photocatalytic performance for rhodamine B dye (consistent removal rate in the 13.96 × 10−3 min−1) compared with free-standing Cu0.5Mg0.5Fe2O4 and TiO2 materials. The recyclability and photocatalytic mechanism of Cu0.5Mg0.5Fe2O4–TiO2 are also well discussed.
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•A new hybrid Cu0.5Mg0.5Fe2O4–TiO2 material was designed and fabricated.•A 2.86-eV-bandgap-energy semiconductor harvests photon energy in the visible region.•High photocatalytic performance with a good degrading rate constant was obtained.•High photocatalytic performance with stability was achieved.•Separation/recovery from the treated solution was achieved using an external magnet.
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•Chitosan/gum arabic edible coating was supplemented with antibacterial ZnO nanoparticles.•Antibacterial ZnO nanoparticles were added to chitosan/gum arabic edible coating.•Avocado ...surface with ZnO/chitosan/gum arabic edible coating was characterized.•Physicochemical properties of ZnO- coated avocados were determined.•ZnO/chitosan/gum arabic coating significantly enhanced the freshness of avocado.
Edible coatings or films are considered effective and sustainable in preventing the waste of millions of tons of fruits and vegetables resulting from decay and deterioration. In this study, we propose a new edible coating formulation to preserve avocado. The edible coating consisted of film-forming mixed polysaccharides (chitosan and gum arabic) supplemented with non-toxic zinc oxide (ZnO) nanoparticles using the mixing method. ZnO nanoparticles with diameters ranging from 10 to 40 nm were synthesized using hydrothermal method. The prepared ZnO and ZnO/chitosan/gum arabic edible coatings were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the edible film coated on the avocado's surface was smooth and uniform with an even distribution of ZnO nanoparticles in the film matrix. The physicochemical properties of avocados, such as appearance and brightness; weight; firmness; and reducing sugar content significantly improved after coating with the ZnO/chitosan/gum arabic edible film as compared to the uncoated samples. The best protective performance was achieved when the coating’s optimum ZnO concentration was 0.3 % w/w. While the uncoated avocados rotted after seven days of storage in room temperature, the coated avocados remained fresh under similar storage conditions.
In the quest of improving the photocatalytic efficiency of photocatalysts, the combination of two and more semiconductors recently has garnered significant attention among scientists in the field. ...The doping of conductive metals is also an effective pathway to improve photocatalytic performance by avoiding electron/hole pair recombination and enhancing photon energy absorption. This work presented a design and fabrication of porphyrin@g-C3N4/Ag nanocomposite using acid-base neutralization-induced self-assembly approach from monomeric porphyrin and g-C3N4/Ag material. g-C3N4/Ag material was synthesized by a green reductant of Cleistocalyx operculatus leaf extract. Electron scanning microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, and UV–vis spectrometer were utilized to analyse the properties of the prepared materials. The prepared porphyrin@g-C3N4/Ag nanocomposite showed well integration of porphyrin nanostructures on the g-C3N4/Ag's surface, in which porphyrin nanofiber was of the diameter in nanoscales and the length of several micrometers, and Ag NPs had an average particle size of less than 20 nm. The photocatalytic behavior of the resultant nanocomposite was tested for the degradation of Rhodamine B dye, which exhibited a remarkable RhB photodegrading percentage. The possible mechanism for photocatalysis of the porphyrin@g-C3N4/Ag nanocomposite toward Rhodamine B dye was also proposed and discussed.
•Porphyrin-based nanomaterial prepared via self-assembly approach successfully.•A new porphyrin@g-C3N4/Ag nanocomposite with full characterizations was successfully prepared.•Porphyrin nanofiber/g-C3N4/Ag hybrid material formed to improve photon energy harvesting.•Porphyrin@g-C3N4/Ag nanocomposite showed 97% removal of pollutants.•Photocatalytic mechanism of g-C3N4@porphyrin for organic dye degradation was proposed.
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•Recent pretreatment techniques for improving anaerobic digestion of sewage sludge were reviewed.•Sludge pretreatment ameliorates anaerobic digestion and increases the biogas ...yield.•Pretreatment technique efficiency depends on sewage sludge composition.•Microbes play a crucial role in sewage sludge stabilization.•Very few pretreatment techniques are suitable for full-scale implementation.
Anaerobic digestion (AD) of sewage sludge is one of the most efficient, effective, and environmentally sustainable remediation techniques; however, the presence of complex floc structures, hard cell walls, and large amounts of molecular organic matter in the sludge hinder AD hydrolysis. Consequently, sewage sludge pretreatment is a prerequisite to accelerate hydrolysis and improve AD efficiency. This review focuses on pretreatment techniques for improving sewage sludge AD, which include mechanical, chemical, thermal, and biological processes. The various pretreatment process effects are discussed in terms of advantages and disadvantages, including their effectiveness, and recent achievements are reviewed for improved biogas production.
In recent years, pharmaceutical active compounds (PhACs) have attained global prevalence. The behavior of PhACs in agricultural soils is complex and depends on several factors, such as the nature of ...the compounds and their physicochemical characteristics, which affect their fate and potential threats to human health, ecosystems, and the environment. The detection of residual pharmaceutical content is possible in both agricultural soils and environmental matrices. PhACs are commonly found in agricultural soil, with concentrations varying significantly, ranging from as low as 0.048 ng g−1 to as high as 1420.76 mg kg−1. The distribution and persistence of PhACs in agriculture can lead to the leaching of these toxic pollutants into surface water, groundwater, and vegetables/plants, resulting in human health risks and environmental pollution. Biological degradation or bioremediation plays a critical role in environmental protection and efficiently eliminates contamination by hydrolytic and/or photochemical reactions. Membrane bioreactors (MBRs) have been investigated as the most recent approach for the treatment of emerging persistent micropollutants, including PhACs, from wastewater sources. MBR- based technologies have proven to be effective in eliminating pharmaceutical compounds, achieving removal rates of up to 100%. This remarkable outcome is primarily facilitated by the processes of biodegradation and metabolization. In addition, phytoremediation (i.e., constructed wetlands), microalgae-based technologies, and composting can be highly efficient in remediating PhACs in the environment. The exploration of key mechanisms involved in pharmaceutical degradation has revealed a range of approaches, such as phytoextraction, phytostabilization, phytoaccumulation, enhanced rhizosphere biodegradation, and phytovolatilization. The well-known advanced/tertiary removal of sustainable sorption by biochar, activated carbon, chitosan, etc. has high potential and yields excellent quality effluents. Adsorbents developed from agricultural by-products have been recognized to eliminate pharmaceutical compounds and are cost-effective and eco-friendly. However, to reduce the potentially harmful impacts of PhACs, it is necessary to focus on advanced technologies combined with tertiary processes that have low cost, high efficiency, and are energy-saving to remove these emerging pollutants for sustainable development.
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•PhACs behavior in agricultural soils is a complex process and has become a global issue.•PhACs are commonly found in agricultural soil, ranging from 0.048 ng g−1 to 1420.76 mg kg−1.•The presence of PhACs in agriculture poses risks to food safety and security.•Antibiotic residues have adverse effects on flora, fauna, and human health through food chains.•MBR-based technologies effectively remove PhACs, achieving up to 100% removal.
A pilot-scale hybrid constructed wetland with vertical flow and horizontal flow in series was constructed and used to investigate organic material and nutrient removal rate constants for wastewater ...treatment and establish a practical predictive model for use. For this purpose, the performance of multiple parameters was statistically evaluated during the process and predictive models were suggested. The measurement of the kinetic rate constant was based on the use of the first-order derivation and Monod kinetic derivation (Monod) paired with a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). Both the Lindeman, Merenda, and Gold (LMG) analysis and Bayesian model averaging (BMA) method were employed for identifying the relative importance of variables and their optimal multiple regression (MR). The results showed that the first-order–PFR (M2) model did not fit the data (P > 0.05, and R2 < 0.5), whereas the first-order–CSTR (M1) model for the chemical oxygen demand (CODCr) and Monod–CSTR (M3) model for the CODCr and ammonium nitrogen (NH4−N) showed a high correlation with the experimental data (R2 > 0.5). The pollutant removal rates in the case of M1 were 0.19 m/d (CODCr) and those for M3 were 25.2 g/m2∙d for CODCr and 2.63 g/m2∙d for NH4-N. By applying a multi-variable linear regression method, the optimal empirical models were established for predicting the final effluent concentration of five days' biochemical oxygen demand (BOD5) and NH4-N. In general, the hydraulic loading rate was considered an important variable having a high value of relative importance, which appeared in all the optimal predictive models.
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•A two-stage hybrid constructed wetland (HCW) system was constructed and evaluated for performance.•Multi-kinetic models for predicting the HCW performance were applied to analyze the results.•The HCW performance was modeled using linear and nonlinear regression analysis.•An optimal predictive model for experimental development of HCW was presented.
Adsorption in the continuous mode plays a significant role in wastewater treatment. In this study, Mimosa pigra-derived biochar modified with 2 M AlCl3 salt was used to pack a lab-scale column to ...eliminate PO43− from aqueous solutions. The influence of the operational factors, such as inlet PO43− concentration (25–100 mg/L), flow rate (6–18 mL/min), and biochar bed height (1.5–4.5 cm), on the breakthrough curve was evaluated. The kinetic models of Adam–Bohart and Yoon–Nelson were utilized to analyze the experimental results. The best conditions were determined to be the influent PO43− strength of 50 mg/L, injection speed of 6 mL/min, and column height of 4.5 cm. These results can be applied in the design of large-scale columns for the sequestration of PO43− from wastewater.
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•Phosphate was successfully removed using fixed-bed modified biochar column.•The inlet PO43−, flow rate, and bed height affected the breakthrough curve.•The optimal conditions were 50 mg/L of PO43−, 6 mL/min flow rate, and 4.5 cm height.•Adam–Bohart and Yoon–Nelson models were utilized to describe experimental results.
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