Green synthesis of nanomaterials - a scientometric assessment

The green synthesis of engineered nanomaterials (NMs) has deserved an enormous academic interest and huge financial investments during the last decades. However, this prominent position has not been followed by the rapid commercialization of NMs for real applications thus rendering their practical usefulness very doubtful and the appropriateness of novel investments in the field highly questionable. The present manuscript presents the first scientometric study on the green synthesis of NMs aiming to survey the scientific progress in this particular field and identify its main gaps while providing applicable suggestions to facilitate the knowledge transfer from laboratories to real full scale production and applications. The research on green synthesis of nanomaterials published in Web of Science during the period 1991–2019 is here carefully analyzed. Overall, 9 scientometric indicators are employed to interpret the results retrieved from the 8761 documents collected. It is found that 107 countries and nearly 22,400 authors have contributed to this subject, hence highlighting the relevance of this topic. The keywords spectrum is dominated by the term “nanoparticle” which full adoption takes place at the beginning of the 21st century. Some few years later, a batch of words like “silver nanoparticle”, “gold nanoparticle” and “nanocomposite” reaches a significant impact reflecting the emergence of commercial applications for these nanomaterials. It is only in 2009 that the keyword “green synthesis” gains strength, followed then by “biosynthesis” in 2010, making it evident a trend towards environmentally friendly reagents. The number of publications on green synthesis of nanomaterials displays up to now a sigmoidal like growth pattern, which points actually to a decrease on new arrivals, thus suggesting a possible forthcoming decline in this field. However, the analysis carried out in the present work allows identifying various gaps related to sustainability, which, if appropriately addressed, may contribute to a resurgence of the research on nanomaterials synthesis while fostering more frugal approaches on material synthesis tendencies.publishe

Microstructural Evolutions and its Impact on the Corrosion Behaviour of Explosively Welded Al/Cu Bimetal

In this study, the microstructural evolutions and corrosion resistance of aluminium/copper joint fabricated through explosive welding process have been thoroughly investigated, while stand-off distance was variable. Microstructural analyses demonstrate that, regardless of grain refinement in the welding boundary, increasing the stand-off space is followed by a higher thickness of the localized melting pool. X-Ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses recognized the binary intermetallic layers as a combination of Al2Cu and AlCu. Polarization and electrochemical impedance spectroscopy (EIS) corrosion tests revealed that a higher stand-off distance resulted in the increment of corrosion potential, current rate, and concentration gradient at the interface owing to the remarkable kinetic energy of the collision, which impaired corrosion resistance

Catalytic Ozonation of the Secondary Effluents from the Largest Chinese Petrochemical Wastewater Treatment Plant—A Stability Assessment

Effluents discharged from petrochemical facilities are complex and composed of various types of highly toxic contaminants, which necessitates the development of sustainable treatment technologies. Stability is among the most important sustainability criteria of the wastewater treatment processes. In the present manuscript, the standard-reaching rate (η) index was used to evaluate the stability of the catalytic ozonation process for treating the secondary effluent from the petrochemical industry. A pilot-scale device was designed and implemented for catalytic ozonation. The effluents were taken from the secondary sedimentation tank of a petrochemical wastewater treatment plant in China. A commercially available γ-Al2O3 was used as the catalyst after a pre-treatment heating step. The catalyst was characterized using scanning electron microscopy. Three mathematical statistics indexes, discrete coefficient (Vσ), skewness coefficient (Cso), and range coefficient (VR), were used to analyze the results achieved from the catalytic ozonation process. Continuous operation of the pilot-scale device was monitored for 9 months under an ozone concentration of 36 mg/L and the contact oxidation time of 1 h. The results demonstrated that the stability evaluation grades of chemical oxygen demand (COD) and suspended solids (SS) in the effluent of the catalytic ozonation system were both 3 and A, indicating that the process was relatively stable over a long period of application. The effluent COD compliance grade was also calculated as B, indicating that the effluent COD does not meet the standard and the process parameters need to be further optimized. When the reflux ratio is 150%, the removal rate of COD is the highest (38.2%) and the COD of effluent is 49.34 mg/L. Meanwhile, to enhance the efficiency and stability of the system, the ozone concentration and the two-stage aeration ratio are 40 mg/L and 4:1, respectively. Moreover, the presence of SS in the water of the catalytic ozonation system will result in the waste of ozone and reduce the utilization rate of ozone

Catalytic Ozonation of the Secondary Effluents from the Largest Chinese Petrochemical Wastewater Treatment Plant—A Stability Assessment

Effluents discharged from petrochemical facilities are complex and composed of various types of highly toxic contaminants, which necessitates the development of sustainable treatment technologies. Stability is among the most important sustainability criteria of the wastewater treatment processes. In the present manuscript, the standard-reaching rate (η) index was used to evaluate the stability of the catalytic ozonation process for treating the secondary effluent from the petrochemical industry. A pilot-scale device was designed and implemented for catalytic ozonation. The effluents were taken from the secondary sedimentation tank of a petrochemical wastewater treatment plant in China. A commercially available γ-Al2O3 was used as the catalyst after a pre-treatment heating step. The catalyst was characterized using scanning electron microscopy. Three mathematical statistics indexes, discrete coefficient (Vσ), skewness coefficient (Cso), and range coefficient (VR), were used to analyze the results achieved from the catalytic ozonation process. Continuous operation of the pilot-scale device was monitored for 9 months under an ozone concentration of 36 mg/L and the contact oxidation time of 1 h. The results demonstrated that the stability evaluation grades of chemical oxygen demand (COD) and suspended solids (SS) in the effluent of the catalytic ozonation system were both 3 and A, indicating that the process was relatively stable over a long period of application. The effluent COD compliance grade was also calculated as B, indicating that the effluent COD does not meet the standard and the process parameters need to be further optimized. When the reflux ratio is 150%, the removal rate of COD is the highest (38.2%) and the COD of effluent is 49.34 mg/L. Meanwhile, to enhance the efficiency and stability of the system, the ozone concentration and the two-stage aeration ratio are 40 mg/L and 4:1, respectively. Moreover, the presence of SS in the water of the catalytic ozonation system will result in the waste of ozone and reduce the utilization rate of ozone

Additive and additive-free treatment technologies for pulp and paper mill effluents: Advances, challenges and opportunities

In the present manuscript, novel effluent treatment processes for pulp and paper mill effluents are divided into two categories: a) those involving the use of chemical additives and b) those which are free of such chemicals. It is especially of high importance for pulp and paper industry to adopt the most efficient and cost-effective treatment methods. This paper critically reviews the recent studies on the treatment of pulp and paper mill effluents while providing suggestions for further studies on the application of various physic-chemical and biological methods for the treatment of such complex effluents containing a number of recalcitrant pollutants. Keywords: Pulp and paper industry, Industrial effluents, Chemical additives, Non-additive treatment processe

Using models for estimation of leaf area index in Cucurbita pepo L.

In order to find plant growth characteristic relationships with leaf area index in Pumpkin (Cucurbita pepo L.), an experiment was conducted based on randomized complete block design with three replications. Three planting dates (Apr. 20, May 21 and Jun. 21) performed at the research field of Abooreihan Campus, the University of Tehran, Pakdasht, Tehran, Iran, in 2009–2010 cropping season. Sampling was performed during the whole growing season and leaf area (LA), leaf no. per plant, leaf dry weight (LDW), leaf fresh weight (LFW), node no. per main stem and plant height, were measured. The aim of this study was to collect and evaluate nonlinear regression models in the plant growth characteristic studies (exponential, Gaussian, linear, quadratic, symmetric, sigmoid). Root Mean Square Error (RMSE), the standard error of the estimate (SE) and coefficient of determination (R2) were used to find the appropriate model(s). The result showed that, the linear model predicted significant relationships between LAI and LA (R2 = 90), LAI and leaf no. per plant (R2 = 90), LAI and node no. per main stem (R2 = 90), LAI and LDW (R2 = 98) and LAI and LFW (R2 = 98). These result showed that the linear model can be used for estimation of LAI Pumpkin, especially where there is no LAI-meter available. Keywords: Pumpkin, Allometric relationships, Leaf area, Vegetative characteristics, Linear mode

ZnO/γ-Fe2O3/Bentonite: An Efficient Solar-Light Active Magnetic Photocatalyst for the Degradation of Pharmaceutical Active Compounds

For applications related to the photocatalytic degradation of environmental contaminants, engineered nanomaterials (ENMs) must demonstrate not only a high photocatalytic potential, but also a low tendency to agglomeration, along with the ability to be easily collected after use. In this manuscript, a two-step process was implemented for the synthesis of ZnO, ZnO/Bentonite and the magnetic ZnO/γ-Fe2O3/Bentonite nanocomposite. The synthesized materials were characterized using various techniques, and their performance in the degradation of pharmaceutical active compounds (PhACs), including ciprofloxacin (CIP), sulfamethoxazole (SMX), and carbamazepine (CBZ) was evaluated under various operating conditions, namely the type and dosage of the applied materials, pH, concentration of pollutants, and their appearance form in the medium (i.e., as a single pollutant or as a mixture of PhACs). Among the materials studied, ZnO/Bentonite presented the best performance and resulted in the removal of ~95% of CIP (5 mg/L) in 30 min, at room temperature, near-neutral pH (6.5), ZnO/Bentonite dosage of 0.5 g/L, and under solar light irradiation. The composite also showed a high degree of efficiency for the simultaneous removal of CIP (~98%, 5 mg/L) and SMX (~97%, 5 mg/L) within 30 min, while a low degradation of ~5% was observed for CBZ (5 mg/L) in a mixture of the three PhACs. Furthermore, mechanistic studies using different types of scavengers revealed the formation of active oxidative species responsible for the degradation of CIP in the photocatalytic system studied with the contribution of h+ (67%), OH (18%), and ·O2− (10%), and in which holes (h+) were found to be the dominant oxidative species