Transport and retention of functionalized graphene oxide nanoparticles in saturated/unsaturated porous media: Effects of flow velocity, ionic strength and initial particle concentration.

The widespread use of nanomaterials has raised the threat of nanoparticles (NPs) infection of soils and groundwater resources. This research aims to investigate three parameters including flow velocity, ionic strength (IS), and initial particle concentration effects on transport behavior and retention mechanism of functionalization form of graphene oxide with polyvinylpyrrolidone (GO-PVP). The transport of GO-PVP was investigated in a laboratory-scale study through saturated/unsaturated (Saturation Degree = 0.91) sand columns. Experiments were conducted on flow velocity from 1.20 to 2.04 cm min-1, initial particle concentration from 10 to 50 mg L-1, and IS of 5-20 mM. The retention of GO-PVP was best described using the one-site kinetic attachment model in HYDRUS-1D, which accounted for the time and depth-dependent retention. According to breakthrough curves (BTCs), the lower transport related to the rate of mass recovery of GO-PVP was obtained by decreasing flow velocity and initial particle concentration and increasing IS through the sand columns. Increasing IS could improve the GO-PVP retention (based on katt and Smax) in saturated/unsaturated media; katt increases from 2.81 × 10-3 to 3.54 × 10-3 s-1 and Smax increases from 0.37 to 0.42 mg g-1 in saturated/unsaturated conditions, respectively. Our findings showed that the increasing retention of GO-PVP through the sand column under unsaturated condition could be recommended for the reduction of nanoparticles danger of ecosystem exposure.

A novel combined system for efficient nitrate removal using a continuous flow electrocoagulation and sand filtration (FECF) reactor: Statistical analysis by Taguchi design.

In this study, a new hybrid bench-scale electrocoagulation-sand filtration (FECF) reactor was developed for purifying nitrate-contaminated samples. Before and after electrochemical treatment, two sand filters were included in this continuous system to facilitate the purification procedure, and the contaminated water flows horizontally through the entire system according to a specific hydraulic gradient within the reactor, resulting in water purification. Significant improvement in treatment performance was observed due to the presence of metal hydroxides in the second filter media that were not fully involved in the electrocoagulation treatment. Energy dispersive X-ray (EDX) analysis was performed to detect metal hydroxide species in the sand media, and the need for filter regeneration was evaluated by monitoring changes in the system flow rate. Moreover, an evaluation of the effects of different factors including operating time, current intensity, initial pH, type of anode and cathode, initial nitrate concentration, hydraulic head level inside the reactor, number of electrodes, and NaCl electrolyte concentration on the performance of nitrate removal was conducted through the Taguchi design. Further, ANOVA analysis verified the accuracy of the predicted model, and the variables were classified based on their relative importance in the FECF process. According to the regression model, 97% of nitrates were removed with Al electrodes as anode and Fe as cathode, 70 min purification time, current intensity of 3 A, 100 mg/l initial nitrate concentration, pH 8, electrolyte concentration of 1 g/l, electrode number of 6, and 1.5 cm head level.

A review of various strategies in e-waste management in line with circular economics.

Waste management of electrical and electronic equipment has become a key challenge for electronics manufacturers due to globalization and the rapid expansion of information technology. As the volume of e-waste grows, legal departments lack the infrastructure, technology, and ability to collect and manage it environmentally soundly. Government laws, economic reasons, and social issues are important considerations in e-waste management. The circular economy concept is built on reusing and recycling goods and resources. A novel idea called the circular economy might prevent the negative consequences brought on by the exploitation and processing of natural resources while also having good effects such as lowering the demand for raw materials, cutting down on the use of fundamental resources, and creating jobs. To demonstrate the significance of policy implementation, the necessity for technology, and the need for societal awareness to build a sustainable and circular economy, the study intends to showcase international best practices in e-waste management. This study uses circular economy participatory implementation methods to provide a variety of possible approaches to assist decision-makers in e-waste management. The purpose of this article is to review the most accepted methods for e-waste management to emphasize the importance of implementing policies, technology requirements, and social awareness in creating a circular economy. To conclude, this paper highlights the necessity of a common legal framework, reform of the informal sector, the responsibility of different stakeholders, and entrepreneurial perspectives.

Marine plastics, circular economy, and artificial intelligence: A comprehensive review of challenges, solutions, and policies.

Global plastic production is rapidly increasing, resulting in significant amounts of plastic entering the marine environment. This makes marine litter one of the most critical environmental concerns. Determining the effects of this waste on marine animals, particularly endangered organisms, and the health of the oceans is now one of the top environmental priorities. This article reviews the sources of plastic production, its entry into the oceans and the food chain, the potential threat to aquatic animals and humans, the challenges of plastic waste in the oceans, the existing laws and regulations in this field, and strategies. Using conceptual models, this study looks at a circular economy framework for energy recovery from ocean plastic wastes. It does this by drawing on debates about AI-based systems for smart management. In the last sections of the present research, a novel soft sensor is designed for the prediction of accumulated ocean plastic waste based on social development features and the application of machine learning computations. Plus, the best scenario of ocean plastic waste management with a concentration on both energy consumption and greenhouse gas emissions is discussed using USEPA-WARM modeling. Finally, a circular economy concept and ocean plastic waste management policies are modeled based on the strategies of different countries. We deal with green chemistry and the replacement of plastics derived from fossil sources.

Challenges and opportunities of lignocellulosic biomass gasification in the path of circular bioeconomy.

The energy deficiency issues and intense environmental pollution have exacted the production of biofuels which are both renewable and sustainable and can be used to displace fossil fuels. The raw material for manufacturing second-generation biofuels is lignocellulosic biomass (LCB), which is widely available. LCB bioprocessing to produce high-value bio-based products has been the subject of attention. Biomass gasification is a powerful technology to achieve sustainable development goals, reduce reliance on fossil fuels, and reduce environmental concerns. This paper, will provide an overview of the LCB structures and the gasification process. Also, consistent with the concept of "circular bio-economy", this study focuses on the role of LCB gasification in the environmental impacts, and how gasification can be effective in the pathway of circular bio-economy. The current challenges to gasification and biorefinery and future perspectives are also presented.

Investigating the potential of sustainable use of green silica in the green tire industry: a review.

Undoubtedly, with the increasing emission of greenhouse gases and non-biodegradable wastes as the consequence of over energy and material consumption, the demands for environmentally friendly products are of significant importance. Green tires, a superb alternative to traditional tires, could play a substantial part in environmental protection owing to lower toxic and harmful substances in their construction and their higher decomposition rate. Furthermore, manufacturing green tires using green silica as reinforcement has a high capacity to save energy and reduce carbon dioxide emissions, pollution, and raw material consumption. Nevertheless, their production costs are expensive in comparison with conventional tires. In this review article, by studying green tires, the improvement of silica-rubber mixing, as well as the production of green silica from agricultural wastes, were investigated. Not only does the consumption of agricultural wastes save resources considerably, but it also could eventually lead to the reduction of silica production expenses. The cost of producing green silica is about 50% lower than producing conventional silica, and since it weighs about 17% of green silica tires, it can reduce the cost of producing green rubber. Accordingly, we claim that green silica has provided acceptable properties of silica in tires. Apart from the technical aspect, environmental and economic challenges are also discussed, which can ultimately be seen as a promising prospect for the use of green silica in the green tire industry.

Performance of novel GO-Gly/HNTs and GO-GG/HNTs nanocomposites for removal of Pb(II) from water: optimization based on the RSM-CCD model.

For the first time, in this study, two novel glycogen-graphene oxide/halloysite nanotubes (GO-Gly/HNTs) and guar gum-graphene oxide/halloysite nanotubes (GO-GG/HNTs) nanocomposites were synthesized as the adsorbents for removal of Pb(II) from water, and the ionic liquid was used in the synthesis as a green solvent. According to the SEM, TEM, EDS, BET, zeta potential, FTIR, and XRD results, GO-Gly/HNTs and GO-GG/HNTs were synthesized successfully. Response surface methodology (RSM) was applied to optimize the experimental conditions. Nanocomposites followed the Langmuir equilibrium model and were best fitted to the pseudo-second-order model. According to the thermodynamic model, the adsorption process was endothermic. Due to several features, these two novel nanocomposites can be considered the proper candidate for Pb(II) removal from water and wastewater. First, these nanocomposites have good adsorption capacity for Pb(II) removal, which is 219 mg/g for GO-Gly/HNTs and 315 mg/g for GO-GG/HNTs. Moreover, nanocomposites can be recycled with proper adsorption capacity after four repeated cycles. These materials can be used to remove Pb(II) from water in the presence of other contaminants because nanocomposites have selective tendency toward Pb(II) in the presence of other pollutants such as Cd2+, Cu2+, Cr2+, and Co2+. In addition, the presence of Ca2+, Mg2+, Na+, and K+ improve Pb(II) removal. Finally, possible mechanisms for each nanocomposite were represented.

Fabrication of Bio-Nanocomposite Based on HNT-Methionine for Controlled Release of Phenytoin.

In this study, a novel promising approach for the fabrication of Halloysite nanotube (HNT) nanocomposites, based on the amino acid named Methionine (Met), was investigated. For this purpose, Met layered on the outer silane functionalized surface of HNT for controlled release of Phenytoin sodium (PHT). The resulting nanocomposite (MNT-g-Met) was characterized by FTIR, XRD, Zeta potential, TGA, TEM and FE-SEM. The FT-IR results showed APTES and Met peaks, which proved the modification of the HNTs. The zeta-potential results showed the interaction between APTES (+53.30) and Met (+38.80) on the HNTs (-30.92). The FE-SEM micrographs have displayed the grafting of Met on the modified HNTs due to the nanotube conversion to a rough and indistinguishable form. The amount of encapsulation efficiency (EE) and loading efficiency (LE) of MNT-g-Met was 74.48% and 37.24%, while pure HNT was 57.5%, and 28.75%, respectively. In-vitro studies showed that HNT had a burst release (70% in 6 h) in phosphate buffer while MNT-g-Met has more controlled release profile (30.05 in 6 h) and it was found to be fitted with the Korsmeyer-Peppas model. Due to the loading efficiency and controlled release profile, the nanocomposite promote a good potential for drug delivery of PHT.

Environmental impact of increased soap consumption during COVID-19 pandemic: Biodegradable soap production and sustainable packaging.

A year into the coronavirus disease 2019 pandemic, the role of washing hands with soap and hand disinfectants is unavoidable as a primary way to control the infection spread in communities and healthcare facilities. The extraordinary surge in demand for handwashing products has led to environmental concerns. Since soaps are complex mixtures of toxic and persistent active ingredients, the prudent option is to promote eco-friendly replacements for the current products. On the other hand, with the increase in soap packaging waste production, soap packaging waste management and recycling become essential to reduce environmental impact. This systematic review aimed to collect some recent methods for identifying biodegradable and sustainable raw materials to produce and package cleaning agents, especially soap.

Mechanistic aspects of poly(ethylene terephthalate) recycling-toward enabling high quality sustainability decisions in waste management.

Since plastic waste pollution is a severe environmental concern in modern life, the demand for recycling poly(ethylene terephthalate) (PET) has increased due to its versatile applications. Taking advantage of plastic recycling methods creates the chances of minimizing overall crude oil-based materials consumption, and as a result, greenhouse gasses, specifically CO2, will be decreased. Although many review articles have been published on plastic recycling methods from different aspects, a few review articles exist to investigate the organic reaction mechanism in plastic recycling. This review aims to describe other processes for recycling bottle waste of PET, considering the reaction mechanism. Understanding the reaction mechanism offers practical solutions toward protecting the environment against disadvantageous outgrowths rising from PET wastes. PET recycling aims to transform into a monomer/oligomer to produce new materials from plastic wastes. It is an application in various fields, including the food and beverage industry, packaging, and textile applications, to protect the environment from contamination and introduce a green demand for the near future. In this review, the chemical glycolysis process as an outstanding recycling technique for PET is also discussed, emphasizing the catalysts' performance, reaction conditions and methods, degradation agents, the kinetics of reactions, and reprocessing products. In general, a correct understanding of the PET recycling reaction mechanism leads to making the right decisions in waste management.

Direct and indirect effects of SARS-CoV-2 on wastewater treatment.

The novel SARS-CoV-2 is expanding internationally. While the current focus is on limiting its transmission from direct contact with infected patients and surfaces during the pandemic, the secondary transmission potential via sewage should not be underestimated, especially in low-income and developing countries with weak wastewater treatment technologies. Recent studies have indicated SARS-CoV-2 positivity also be detected in the feces of patients. Therefore, the risk of transmission and infection can be increased into sewage by the fecal-oral way, mainly in some parts of the globe with a high amount of open defecation. This review collected scattered data and recent studies about the direct and indirect effects of coronavirus in the water cycle. The direct impacts of COVID-19 on wastewater are related to the presence of the coronavirus and suitable viral removal methods in different phases of treatment in wastewater treatment plants. The indirect effects of COVID-19 on wastewater are related to the overuse of cleaning and disinfecting products to protect against viral infection and the overuse of certain drugs to protect against virus or novel mental problems and panic to COVID-19 and consequently their presence in wastewater. This unexpected situation leads to changes in the quality of wastewater and brings adverse and harmful effects for the human, aquatic organisms, and the environment. Therefore, applying effective wastewater treatment technologies with low toxic by-products in wastewater treatment plants will be helpful to prevent the increasing occurrence of these extra contaminants in the environment.

Key factors affecting graphene oxide transport in saturated porous media.

This study focuses on the transport in porous media of graphene oxide nanoparticles (GONP) under conditions similar to those applied in the generation of in-situ reactive zones for groundwater remediation (i.e. GO concentration of few tens of mg/l, stable suspension in alkaline solution). The experimental tests evaluated the influence on GO transport of three key factors, namely particle size (300-1200 nm), concentration (10-50 mg/L), and sand size (coarse to fine). Three sources of GONP were considered (two commercial and one synthesized in the laboratory). Particles were stably dispersed in water at pH 8.5 and showed a good mobility in the porous medium under all experimental conditions: after injection of 5 pore volumes and flushing, the highest recovery was around 90%, the lowest around 30% (only for largest particles in fine sand). The particle size was by far the most impacting parameter, with increasing mobility with decreasing size, even if sand size and particle concentration were also relevant. The source of GONP showed a minor impact on the mobility. The transport test data were successfully modeled using the advection-dispersion-deposition equations typically applied for spherical colloids. Experimental and modeling results suggested that GONP, under the explored conditions, are retained due to both blocking and straining, the latter being relevant only for large particles and/or fine sand. The findings of this study play a key role in the development of an in-situ groundwater remediation technology based on the injection of GONP for contaminant degradation or sorption. Despite their peculiar shape, GONP behavior in porous media is comparable with spherical colloids, which have been more studied by far. In particular, the possibility of modeling GONP transport using existing models ensures that they can be applied also for the design of field-scale injections of GONP, similarly to other particles already used in nanoremediation.

Sericin grafted multifunctional curcumin loaded fluorinated graphene oxide nanomedicines with charge switching properties for effective cancer cell targeting.

Fluorinated graphene has recently gained much attention for cancer drug delivery, owing to its peculiar properties including high electronegativity difference, magnetic resonance imaging contrast agent, and the photothermal effect. However, the hydrophobic nature of fluorinated graphene greatly hinders its application as a biological material. Herein, a novel green method is reported for synthesis of a pH-sensitive charge-reversal and water-soluble fluorinated graphene oxide, modified with polyethyleneimine anchored to sericin-polypeptide (FPS). This nanocarrier was further loaded with curcumin (Cur), and characterized as a nanocarrier for anti-cancer drug delivery. The synthesized nanocarriers contain two different pH-sensitive amide linkages, which are negatively charged in blood pH (≈7.4) and can prolong circulation times. The amide linkages undergo hydrolysis once they reach the mildly acidic condition (pH≈6.5, corresponding to tumor extracellular matrix), and subsequently once reached the lower acidic condition (pH≈5.5, corresponded to endo/lysosomes microenvironment), the FPS charge can be switched to positive (≈+28 mV), which aids the nuclear release. This nanocarrier was designed to selectively enhance cell internalization and nuclear-targeted delivery of curcumin in HeLa, SkBr3 and PC-3 cancer cells. Moreover, FPS-Cur demonstrated high curcumin loading capacity, prolonged curcumin release and promotion of apoptosis in HeLa, SkBr3 and PC-3 cells. Therefore, with its pH-responsive charge-reversal properties, FPS-Cur would be a promising candidate for chemotherapy of cervical, breast and prostate cancers.

Ionic Liquids as Environmentally Benign Electrolytes for High-Performance Supercapacitors.

Electrochemical capacitors (ECs) are a vital class of electrical energy storage (EES) devices that display the capacity of rapid charging and provide high power density. In the current era, interest in using ionic liquids (ILs) in high-performance EES devices has grown exponentially, as this novel versatile electrolyte media is associated with high thermal stability, excellent ionic conductivity, and the capability to withstand high voltages without undergoing decomposition. ILs are therefore potentially useful materials for improving the energy/power performances of ECs without compromising on safety, cyclic stability, and power density. The current review article underscores the importance of ILs as sustainable and high-performance electrolytes for electrochemical capacitors.

Preparation of porous biomass-derived hydrothermal carbon modified with terminal amino hyperbranched polymer for prominent Cr(VI) removal from water.

Herein, a series of functionalized hydrochars with high density of nitrogen-containing functional groups were engineered by co-processing of terminal amino hyperbranched polymer and walnut shell biomass in the hydrothermal carbonization media. Hydrothermal Carbonization with optimized key parameters was implemented to determine the impact of added polymer to the biomass on the properties of the obtained hydrochars. Consequently, the optimum hydrochar which was achieved with the values of 250 °C, 60 min, and 50% (w/w) for temperature, time, and polymer/biomass weight ratio, demonstrated a highly improved surface area of 544 m2.g-1 and the highest adsorption capacity for Cr(VI) removal which was obtained from Freundlich isotherm model and described by the pseudo-second-order kinetic model to be 363.22 mg.g-1 (at pH = 2.0). This work suggests that the co-hydrothermal carbonization promotes the uniform incorporation of polymers into the hydrochar matrix and provides adsorbents for the effective removal of Cr(VI) from water.

Effect of hydrodynamic parameters on nickel removal rate from wastewater by ion flotation.

This study investigated the effect of hydrodynamic parameters on the nickel ion removal in an oscillating grid flotation cell (OGC) with near ideal hydrodynamic environments. Nickel ion was removed in the OGC at various energy inputs (0-2 W/kg), using two bubble sizes (130 and 820 µm) at three surfactant concentrations (SDS/Ni(II) ratio of 1-3) and three air flow rates (1-3 L/min). The results indicated that the energy input has a considerable effect on the ion flotation kinetics and recovery and it is strongly dependent on the cell types (contact environment) and bubble size. Increasing energy input led to an increase in the nickel removal rate due to an increase in the collision rate for bigger bubbles and an optimum flotation rate for smaller bubbles. Nickel removal rate increased around 80% (1.8 times) with an increase in energy input from 0 to 2 W/kg for both bubble sizes. Increasing air flow rate generally led to an increase in the nickel removal rate. A comparison of the effect of energy input on the nickel removal separation efficiency in two different hydrodynamic environments showed that the isotropic and homogeneous contact environment in the OGC is more appropriate than anisotropic and inhomogeneous turbulence in the mechanical cell for ion removal using ion flotation.

Flower-like 3-dimensional hierarchical Co3O4/NiO microspheres for 4-nitrophenol reduction reaction.

Aromatic nitro compounds are toxic and not biodegradable. Therefore, the elimination of nitro groups is very important. Metal catalysts play an important role in the catalytic transformation. We present here flower-like 3D hierarchical Co3O4/NiO microspheres, which are prepared by a chemical precipitation method. The as-prepared catalyst is characterized by FTIR, SEM, TEM, EDS, XRD, XPS and N2 sorption isotherms. They have shown different morphologies such as flower, nanocubes, and hexagonal structure at different calcined temperatures. The synthesized catalyst is tested and used for the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as a reducing agent. The reaction takes place in an aqueous medium at room temperature. The bimetallic catalyst Co3O4/NiO showed good performance and reusability.

The main factors effecting the efficiency of Zn(II) flotation: Optimum conditions and separation mechanism.

In this study, the effects of chemical conditions on the recovery of Zn(II) and water during the ion flotation process were evaluated using a central composite design (CCD) of response surface methodology. The optimum effective parameters including pH, collector and frother concentration were determined. The results showed that the pH and collector concentration were effective factors for the efficiency of Zn(II) flotation. The effects of collector and frother concentration on the characterization of sublate and the complexation of sodium dodecyl sulphate with Zn(II) were studied using scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results show that foam fractionation occurred at a pH of 1.5, 3 and 5.5 and ion flotation at a pH of 8.

Green synthesis of degradable conductive thermosensitive oligopyrrole/chitosan hydrogel intended for cartilage tissue engineering.

Electroactive scaffolds containing conductive polymers can promote tissue repair and regeneration. However, these polymers are non-degradable and cannot be removed from body. To overcome this limitation of conductive polymers, we developed a novel injectable electroactive hydrogel containing pyrrole oligomers which possessed the unique properties of being both electrically conductive and biodegradable. First, pyrrole oligomers were synthesized via chemical polymerization and were found to be amorphous with a non-globular morphology. Then, three different compositions of injectable chitosan/beta glycerophosphate hydrogels containing different concentrations of pyrrole oligomers were synthesized and characterized for chemical structure, morphology, conductivity, swelling ratio, In vitro biodegradation and gelation time. An increase in oligopyrrole content resulted in decreased pore size, and increased gelation time, swelling ratio, conductivity and degradation time. Among all the hydrogel compositions, the sample with pyrrole oligomer:chitosan ratio of 0.1 (w/w) showed the most prominent biodegradability, biocompatibility, electro-activity, swelling ratio and pore size values and was chosen as the optimal electroactive hydrogel composition in this work.

The nickel ion removal prediction model from aqueous solutions using a hybrid neural genetic algorithm.

Prediction of Ni(II) removal during ion flotation is necessary for increasing the process efficiency by suitable modeling and simulation. In this regard, a new predictive model based on the hybrid neural genetic algorithm (GANN) was developed to predict the Ni(II) ion removal and water removal during the process from aqueous solutions using ion flotation. A multi-layer GANN model was trained to develop a predictive model based on the important effective variables on the Ni(II) ion flotation. The input variables of the model were pH, collector concentration, frother concentration, impeller speed and flotation time, while the removal percentage of Ni(II) ions and water during ion flotation were the outputs. The most effective input variables on Ni(II) removal and water removal were evaluated using the sensitivity analysis. The sensitivity analysis of the model shows that all input variables have a significant impact on the outputs. The results show that the proposed GANN models can be used to predict the Ni(II) removal and water removal during ion flotation.