Adsorption is a promising affinity separation technique to target a sorbate in extremely dilute solutions. In this work, methacrylonitrile (MAN)-functionalized resins were investigated to recover volatile fatty acids (VFAs) from a mimicked fermentation broth as an alternative for the already known amine-based resins and non-functionalized poly(styrene-divinylbenzene) (PS-DVB), aiming for high VFA capacity and selectivity.
RESULTS
Next to comparison with commercial PS-DVB resin, also several PS-DVB resins were synthesized as non-functionalized analogues for the new MAN-functionalized resins. For MAN-functionalized resins, the maximum equilibrium VFA loading of about 153 (g acid/kg adsorbent) was found, which is higher than the 125 (g acid/kg adsorbent) for the PS-DVB non-functionalized resins. The water uptake of the PS-DVB resins was with 0.53–0.87 (g water/g adsorbent) significantly lower than for the MAN-DVB resins taking up 0.99–1.85 (g water/g adsorbent).
Elvis Kodzo Ahiahonu, William Wilson Anku, Ashira Roopnarain, Mahloro Hope Serepa-Dlamini, Penny Poomani Govender
BACKGROUND
Microalga-assisted wastewater treatment systems have gained attention for their efficiency in removing nutrients, chemical oxygen demand, toxic heavy metals and other dissolved compounds, while also producing valuable biomass and demonstrating high CO2 biofixation potential. The current research focuses on investigating the municipal wastewater phycoremediation and heavy metal biosorption ability of three indigenous freshwater microalgal strains: Tetradesmus reginae, Tetradesmus obliquus and Chlorella sorokiniana.
RESULTS
The research findings indicate that the microalgal strains T. reginae, T. obliquus and C. sorokiniana exhibited notable performance in biomass accumulation. Specifically, the biomass accumulations were 2.215 ± 0.002, 1.143 ± 0.006 and 0.856 ± 0.021 g L−1, respectively, with initial culture biomasses ranging from 0.5 to 0.6 g L−1. These strains significantly reduced toxic heavy metals (As, 46.86–60.12%; Cd, 52.96–83.18%; Cr, 73.49–82.18%; and Pb, 95.38–96.25%), nutrients (NH4+ & NO3− 100% and PO43− 78–86.41%) as well as chemical oxygen demand (46.02–67.35%), and biosequestered CO2 (0.8–0.18 gCO2 L−1 d−1) during the growth period. Among the strains, T. reginae emerged as the top performer. The Fourier transform infrared spectra of the strain's biomass confirmed the presence of specific functional groups, such as CH, NH, OH and CN, which play a crucial role in ionising and reacting with toxic metal ions and protons in the wastewater.
Sami D Salman, Israa M Rashid, Yussur D Abdulwahab
BACKGROUND
This article presents the simultaneous adsorption of bimetal Cu2+ and Zn2+ from an aqueous solution using activated carbon synthesized from a plum seed precursor by sulfuric acid and microwave activation: plum seeds chemically activated by 45% (w/w) sulfuric acid with 2:1 ratio for 4 h, then carbonized for 2 h at 700 °C and the product obtained activated in a microwave oven for 20 min at 700 W for final of activation. Plum seeds and activated carbon produced were characterized in terms of their physical and chemical composition using Brunauer–Emmett–Teller measurements, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of absorption time, bimetal solution pH, bimetal concentration and dosage of activated carbon on the capacity of adsorption and removal efficiency were studied with Design-Expert software using response surface methodology with the I-optimal method for experimental data analysis.
RESULTS
The results showed that the statistical analysis of Cu2+ and Zn2+ removal efficiency followed the quadratic models generated by Design-Expert software with significant P value (P < 0.0001) and the optimum values of removal efficiencies were 99.9268% for Cu2+ and 99.34% for Zn2+ at an adsorption time of 4.98 h, pH of 7.94, bimetal concentration of 38.467 mg L−1 and adsorbent dose of 1485.294 mg (100 mL)−1. The equilibrium adsorption data were analyzed by Langmuir and Freundlich isotherm models and there was a significant agreement in the results with the Freundlich model with R2 = 0.9841 for Cu2+ and R2 = 0.9927 for Zn2+. Likewise, the data were found to fit with a pseudo-second-order model with R2 = 0.9989 for Cu2+ and R2 = 0.9948 for Zn2+ as compared to a pseudo-first-order model.
Noshin Afshan, Ruba Tariq, Iqra Riaz, Abdul Manan, Azhar Iqbal, Muhammad Ejaz, Amir Sohail, Alina Bari, Sajid Mahmood, Shahid Iqbal, Khalid M Alotaibi, Matar Alshalwi
BACKGROUND
Hydroxyl radical-mediated materials primarily liberate more reactive and acutely lethal hydroxyl radical (•OH) and act as potent bactericidal antibiotics, for example H2O2. Hydroxyl radical possess higher tendency than that of H2O2 to attack various biological molecules such as DNA, proteins and iron–sulfur clusters, and impair their proper functioning, actively leading to strongly potent bactericidal effect. To acquire the desired antimicrobial effect, high concentration of H2O2 is required that has found medically harmful to healthy tissues of humans.
RESULTS
We herein report framework nucleic acid-regulated DNAzyme cluster (FDC) – that is, peroxidase-like hemin-bound G-quadruplex (G4/H) DNAzyme – to amplify the catalytic reduction potential of G4/H complex, leading to high conversion rate of H2O2 to more reactive hydroxyl radical that potentially shows the same antibacterial efficiency at lower and safer H2O2 concentration. Specifically, we have grafted multiple copies of DNAzymes outside framework nucleic acid (FNA) to successively achieve 3–9 orders of magnitude enhancement in catalytic activity and antibacterial efficiency of FDC.
Aerobic fermentation always suffers from nitrogen loss and low humification degree. The objective of this study was to investigate the promotion of phosphate buffer on organic matter degradation and precursor polymerization into humus (HS) in aerobic fermentation, and to analyze the key roles played by different precursors. In order to achieve this, sludge aerobic fermentation tests were conducted on control (CK), phosphate buffer addition treatment (KP) and potassium chloride addition treatment (K).
RESULTS
The HS content of KP treatment exhibited a notable increase compared to the CK and K treatments, with a maximum increase of 38.29%. In addition, phosphate addition improved the nitrogen retention capacity and the complexity of the HS structure. Phosphate buffer enhanced both the polyphenol and Maillard humification pathways by promoting the condensation of precursors (polysaccharides, reducing sugars, polyphenols, amino acids and proteins). Among these precursors, reducing sugars, amino acids and proteins were identified as the key driving precursors of phosphate.
The industrial-scale application of enzymes faces obstacles due to elevated costs and difficulties in stability and reuse. In this study, magnetic spent coffee grounds, an ecotoxic waste, have been utilized successfully for the first time to immobilize β-glucosidase to overcome these challenges.
RESULTS
The spent coffee grounds were magnetized and amine-functionalized, followed by characterization using various techniques. Under optimized conditions, forming an imine bond between the functionalized support and β-glucosidase resulted in a 62% immobilization yield (92.81 mg g−1 enzyme loading) and 12.5 U mg−1 activity after immobilization. A relatively small kinetic change was observed in the Km value (902 to 946 μmol L−1) after immobilization, suggesting minimal hindrance by AMSCG3 on substrate access or product release. Moreover, Glu@AMSCG3 showed exceptional stability (>90% residual activity) within a pH range of 3 to 6 after 2 h of incubation at 25 °C. A residual activity of 87.94% was maintained even at 80 °C and pH 5 after 2 h of incubation compared to the free β-glucosidase, which showed only 6.5% residual activity at the same temperature. When cellobiose was hydrolyzed using Glu@AMSCG3 under optimum conditions, 91.33% cellobiose conversion was achieved initially, and over 79% conversion was maintained for 10 reusability cycles.
Nowadays, research focusing on natural compounds is getting more importance across the globe. Recently, natural bioactive compounds have gained the attention of researchers as a consequence of their exemplary physicochemical properties and exceptional utility in the food and pharma industries. However, separating and concentrating these bioactive compounds from their origin sources still poses a considerable challenge to their profitable commercial usage. The current study focuses on the application of a facile nanofiltration method for recovering betanin from model beetroot extract solutions using a polyamide nanofiltration membrane. Furthermore, the three-parameter Spiegler–Kedem model was used to determine the transport parameters of the membrane and theoretically predict the performance of the membrane. Additionally, variance-based sensitivity analysis methods were deployed to study the sensitivity of different operating and membrane transport parameters.
RESULT
The results indicate that the membrane exhibited the highest rejection of 99% and permeate flux of 3.14 ⨯ 10−5 m3 m−2 s−1 at 0.6 MPa pressure and 600 mL min−1 flow rate. The data obtained through the Spiegler–Kedem model were coherent with the experimental observations. Simulations on sensitivity analysis revealed that specific hydraulic permeability and cross-membrane pressure majorly influence permeate flux and rejection.
Gülayşe Özkaymak, Aybüke Nur Şahan, Elif Yakamercan, Yakup Çakmak, Deniz Uçar
BACKGROUND
Dyes present in textile wastewater can pose various environmental problems, including toxicity, carcinogenicity and mutagenicity, when released into receiving environments. Sulfidogenic bacteria play a crucial role in wastewater treatment by reducing sulfate and producing sulfide through the utilization of organic compounds in water. The resulting sulfide often transfers its electrons to another electron acceptor. This study focused on the treatment of real textile wastewater using an up-flow sulfidogenic column bioreactor.
RESULTS
The reactor was acclimated to sulfate-reducing conditions when influent chemical oxygen demand and sulfate concentrations were 1742 and 2000 mg L−1, respectively. Subsequently, a gradual transition was made from sulfate-reducing conditions to dye-reducing conditions. Throughout the study, the hydraulic retention time was maintained at 1 day.
Bio-electro-Fenton (BEF) systems, specifically microbial fuel cell (MFC) driven electro-Fenton (EF) systems, have gained significant attention in wastewater treatment in recent years. The role of the cathode catalyst in BEF is crucial, as it undergoes O2 reduction via a 2e− oxygen reduction reaction (ORR) to produce H2O2. In this study, we have harnessed the abundant lignocellulosic composition of cocoa pod husk (CPH) to prepare a novel iron-doped heterogeneous Fenton catalyst for the BEF system. Cocoa is typically grown for its wet beans, which constitute only one third of cocoa fruit by weight, while CPH makes up about two-thirds of the weight and is often discarded as by-product or waste. As a result, approximately 10 million tons of CPH are produced globally each year, highlighting the potential for transforming it into a value-added product. To date, CPH has been utilised as a natural fertiliser, soil amendment, biomass fuel, poultry and livestock feed ingredient, and more.
RESULTS
The presence of mesoporous structure, iron content, oxygen containing functional groups, and prominent reduction peaks in cyclic voltammetry validated the Fe-doped cocoa husk biochar's (Fe-CHB) potential to act as an ORR catalyst. The BEF system achieved an open circuit voltage, current, and power densities of 0.697 V, 0.15 A/m2, and 0.040 W/m2, respectively, at an optimum resistance of 350 Ω. Optimisation of the process parameters using RSM and ANN predicted maximum dye removal efficiencies of 93.34% and 92.45%, respectively, at dye and substrate concentrations of 10 mg/L and 1 g/L. These predictions closely aligned with the experimental findings of 92.5%.
In order to improve the catalytic performance and stability of magnetic solid acid for cellulose hydrolysis in the aqueous phase, this study first modified the surface of magnetite (Fe3O4) nanoparticles (NPs) with oleic acid. Then, in an oil-in-water (O/W) emulsion system, polystyrene (PS) was coated on the Fe3O4 NPs through emulsion polymerization. Finally, magnetic solid acid Fe3O4@PS-SO3H was prepared by sulfonation.
RESULTS
The obtained Fe3O4@PS-SO3H was characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, infrared, X-ray diffraction, X-ray photoelectron spectroscopy and thermogravimetric analysis, and its acid densityand magnetic properties determined. Applied to cellulose hydrolysis, it exhibited 35.28 emu·g−1 saturation magnetization and 3.56 mmol·g−1 maximum acid density. At 140 °C and 1:1 acid to substrate ratio, cellulose hydrolysis with Fe3O4@PS-SO3H gave a glucose yield of ≤64.14% in 10 h. The solid acid was conveniently recycled with a magnet and reused for further cellulose hydrolysis. It maintained good catalytic activities after five cycles.
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