Determining biokinetic coefficients for the upflow anaerobic sludge blanket reactor treating sugarcane wastewater in hot climate conditions

Acknowledgements The managing director of Imam Khomeini (pbuh) Agro-Industry in Shushtar and the laboratory expert of Agro-Industry Treatment Plant are highly appreciated for their cooperation in conducting this study.Peer reviewedPostprin

Bulk nanobubbles, generation methods and potential applications

The existence of nanobubbles, especially bulk nanobubbles, remains a mystery mainly due to their stability and longevity, properties that are investigated by many research groups worldwide. At the same time, high efforts are given to develop new generation methods, and so far, their potential uses have spread to high-value applications. Some of them are relevant to drinking water and wastewater treatment, surface cleaning, biomedical, engineering, medical imaging but also in ‘nutritional’” applications such as fishery and agriculture. Although the bulk of nanobubbles generation methods are thorough and known well enough, a remarkable lag is still recorded concerning the detailed explanation of their formation, their special physicochemical properties, and the stability mechanisms. In this short review, a condensed description of the nanobubbles production methods, their major properties, and potential important applications are presented. Emphasis has been given to the results and findings during the research effort of the last four years. © 2021 Elsevier Lt

Acid dye removal from aqueous solution by using neodymium(III) oxide nanoadsorbents

In the current work, neodymium oxide (Nd2O3) nanoparticles were synthesized and characterized by means of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The major aim/investigation of this research was to fit/model and optimize the removal of Acid Blue 92 (AB92) dye from synthetic effluents (aqueous solutions) using the adsorption process based on neodymium oxide (Nd2O3) nanoparticles. To optimize the adsorption conditions, central composite design (CCD) based on response surface methodology (RSM) was applied. The effects of pH (3�9), adsorbent dosage (0.1�1 g/L), initial concentration of AB92 (100�300 mg/L), and contact time (10�100 min) on the adsorption process were investigated. Apart from equilibrium and kinetic experiments, thermodynamic evaluation of the adsorption process was also undertaken. The adsorption process was found to have the best fitting to Langmuir isotherm model and pseudo-second-order kinetic equation. Also, the process was found to be spontaneous and favorable with increased temperature. The optimal conditions found were: pH = 3.15, AB92 concentration equal to 138.5 mg/L, dosage of nanoadsorbent equal to 0.83 g/L, and 50 min as contact time, which resulted in 90.70 AB92 removal. High values for the coefficient of determination, R2 (0.9596) and adjusted R2 (0.9220) indicated that the removal of AB92 dye using adsorption can be explained and modeled by RSM. The Fisher�s F-value (25.4683) denotes that the developed model was significant for AB92 adsorption at a 95 confidence level. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Nanobubbles effect on heavy metal ions adsorption by activated carbon

This study investigates the effect of nanobubbles (NBs) on the adsorption in water. In batch adsorption experiments, as liquid medium deionized water, with or without NBs, was used in order to remove a particular heavy metal. Lead ions (Pb(II)) and low-cost activated carbon produced from pyrolysis of potato peels (ACP) were used as model pollutant and adsorbent material, respectively. The adsorption capacity of Pb(II) was found to be approximately similar either in the presence (Qmax = 171 mg/g) or absence of NBs in water (Qmax = 167 mg/g). On the contrary, the major effect of NBs was to accelerate the adsorption process by 366%. This impressively high acceleration will be the basis in future research to decrease the adsorption equilibrium time and sequentially increase the number of adsorption-desorption cycles in reuse modes. A proposed mechanism exported from the experimental results, in which NBs act as carriers (“buses”), was proposed based on the already known theory; the inherent property of NBs to accept charged particles onto their interface is considered to assist diffusion and penetration phenomena of lead ions into the activated carbon pores. © 2018 Elsevier B.V

Molecular docking and 3D-QSAR studies on the glucocorticoid receptor antagonistic activity of hydroxylated polychlorinated biphenyls

<p>The glucocorticoid receptor (GR) antagonistic activities of hydroxylated polychlorinated biphenyls (HO-PCBs) were recently characterised. To further explore the interactions between HO-PCBs and the GR, and to elucidate structural characteristics that influence the GR antagonistic activity of HO-PCBs, molecular docking and three-dimensional quantitative structure–activity relationship (3D-QSAR) studies were performed. Comparative molecular similarity indices analysis (CoMSIA) was performed using both ligand- and receptor-based alignment schemes. Results generated from the receptor-based model were found to be more satisfactory, with <i>q</i>² of 0.632 and <i>r</i>² of 0.931 compared with those from the ligand-based model. Some internal validation strategies (e.g. cross-validation analysis, bootstrapping analysis and Y-randomisation) and an external validation method were used respectively to further assess the stability and predictive ability of the derived model. Graphical interpretation of the model provided some insights into the structural features that affected the GR antagonistic activity of HO-PCBs. Molecular docking studies revealed that some key residues were critical for ligand–receptor interactions by forming hydrogen bonds (Glu540) and hydrophobic interactions with ligands (Ile539, Val543 and Trp577). Although CoMSIA sometimes depends on the alignment of the molecules, the information provided is beneficial for predicting the GR antagonistic activities of HO-PCB homologues and is helpful for understanding the binding mechanisms of HO-PCBs to GR.</p

Bulk nanobubbles: Production and investigation of their formation/stability mechanism

Nanobubbles (ΝΒs) have attracted concentrated scientific attention due to their unique physicochemical properties and large number of potential applications. In this study, a novel nanobubble generator with low energy demand, operating continuously, is presented. Air and oxygen bulk nanobubbles (NBs@air and NBs@O2) with narrow size distribution and outstanding stability were prepared in water solution. The bulk NBs’ behavior was evaluated taking into consideration the hydrodynamic diameter and ζ-potential as a function of processing time, gas type, pH value and NaCl concentration. According to the results the optimum processing time was 30 min, whereas the effect of water salinity was stronger in NBs@O2 than NBs@air. In order to investigate further the NBs properties, Electron Paramagnetic Resonance (EPR) spectroscopy was applied for quantitative analysis of free radicals following the spin trapping methodology. The mechanism of bulk NBs’ generation and their extremely long-time stability can be attributed mainly to the hydrogen bonding interactions. The formation of a diffusion layer, by absorption of OH− due to electrostatic interaction, contributing to negative surface charge, whereas the interaction of ions with the surface hydroxylic groups provide the equilibrium between the protonation and deprotonation of water and finally the formation of a stable interface layer. A remarkable highlight of this work is the long-time stability of generated bulk NBs which is up to three months. © 2019 Elsevier Inc

Praseodymium-doped cadmium tungstate (CdWO₄) nanoparticles for dye degradation with sonocatalytic process

In the present work, praseodymium-doped cadmium tungstate (Pr-CdWO4) nanoparticles were synthesized, characterized and used as catalysts in a sonocatalytic process to degrade the toxic synthetic azo dye Remazol Black B (RBB). RBB was degraded by 93.9% operating at optimal conditions (pH = 3, C = 100 mg/L, catalyst dosage = 0.35 g/L, T = 298 K and irradiation time100 min) under an ultrasonic bath at 60 kHz. Further, the addition of different radical scavengers and enhancers to the reaction was assessed. It was found that the addition of the radical scavengers sodium sulfate, sodium carbonate, and sodium chloride decreased RBB degradation from 93.9% to 86.0%, 78.0%, and 71.2%, respectively. On the contrary, the addition of the enhancers potassium periodate, peroxydisulfate and hydrogen peroxide slightly increased the RBB degradation from 93.9% to 95.3%, 96.1%, and 98.7%, respectively. The sonocatalytic process resulted in higher RBB degradation than by applying separately sonolysis (34.7%) and the catalyst as an adsorbent (39.5%). The experimental data followed both the pseudo-first-order (PFO) and Langmuir-Hinshelwood (L-H) kinetics models. However, the PFO gave better fitting (R² = 0.993) than the L-H kinetic model (R² = 0.9025) at the same optimum experimental conditions. The obtained results pointed out the sonocatalytic process with Pr-doped CdWO₄ nanoparticles as a promising process for the degradation of azo dyes and other hazardous organic compounds existing in wastewater