Due to the exceptional characteristics which resulted from nanoscale size, such as improved catalysis and adsorption properties as well as high reactivity, nanomaterials have been the subject of ...active research and development worldwide in recent years. Numerous studies have shown that nanomaterials can effectively remove various pollutants in water and thus have been successfully applied in water and wastewater treatment. In this paper, the most extensively studied nanomaterials, zero-valent metal nanoparticles (Ag, Fe, and Zn), metal oxide nanoparticles (TiO2, ZnO, and iron oxides), carbon nanotubes (CNTs), and nanocomposites are discussed and highlighted in detail. Besides, future aspects of nanomaterials in water and wastewater treatment are discussed.
This study was focused on the application of white and blue light emitting diodes (LEDs) as sources for the photocatalytic degradation of organic dyes in liquid phase with visible light. The ...photocatalytic activity of N-doped titanium dioxide, synthesized by direct hydrolysis of titanium tetraisopropoxide with ammonia, was evaluated by means of a batch photoreactor. The bandgap energy of titanium dioxide was moved in the visible range from 3.3 eV to 2.5 eV. The visible light responsive photocatalysts showed remarkably effective activity in decolorization process and in the removal of total organic carbon. Methylene blue was also used as a model dye to study the influence of several parameters such as catalyst weight and initial concentration. The effect of dye on the photocatalytic performance was verified with methyl orange (MO). The results demonstrated that the right selection of operating conditions allows to effectively degrade different dyes with the N-doped TiO2 photocatalysts irradiated with visible light emitted by LEDs.
Zinc Oxide is widely used in many industrial sectors, ranging from photocatalysis, rubber, ceramic, medicine, and pigment, to food and cream additive. The global market is estimated to be USD 3600M ...yearly, with a global production of 10 Mt. In novel applications, size and shape may sensibly increase the efficiency and a new nano-ZnO market is taking the lead (USD 2000M yearly with a capacity of 1 Mt and an expected Compound Annual Growth Rate of 20%/year). The aim of this work was to investigate the possibility of producing zinc oxide nanoparticles by means of a spinning disk reactor (SDR). A lab-scale spinning disk reactor, previously used to produce other nanomaterials such as hydroxyapatite or titania, has been investigated with the aim of producing needle-shaped zinc oxide nanoparticles. At nanoscale and with this shape, the zinc oxide particles exhibit their greatest photoactivity and active area, both increasing the efficiency of photocatalysis and ultraviolet (UV) absorbance. Working at different operating conditions, such as at different disk rotational velocity, inlet distance from the disk center, initial concentration of Zn precursor and base solution, and inlet reagent solution flowrate, in certain conditions, a unimodal size distribution and an average dimension of approximately 56 nm was obtained. The spinning disk reactor permits a continuous production of nanoparticles with a capacity of 57 kg/d, adopting an initial Zn-precursor concentration of 0.5 M and a total inlet flowrate of 1 L/min. Product size appears to be controllable, and a lower average dimension (47 nm), adopting an initial Zn-precursor concentration of 0.02 M and a total inlet flow-rate of 0.1 L/min, can be obtained, scarifying productivity (0.23 kg/d). Ultimately, the spinning disk reactor qualifies as a process-intensified equipment for targeted zinc oxide nanoparticle production in shape in size.
Olive oil production is one of the important industrial sectors within the agro-food framework of the Mediterranean region, economically important to the people working in this sector, although there ...is also a threat to the environment due to residues. The main wastes of the olive oil extraction process are olive mill wastewater (OMW) and olive husks which also require proper treatment before dismissal. In this research work, the main goal is to introduce grey relational analysis, a technique for multi-response optimization, to the coagulation and flocculation process of OMW to select the optimum coagulant dosage. The coagulation and flocculation process was carried out by adding aluminum sulfate (Alum) to the waste stream in different dosages, starting from 100 to 2000 mg/L. In previous research work, optimization of this process on OMW was briefly discussed, but there is no literature available that reports the optimal coagulant dosage verified through the grey relational analysis method; therefore, this method was applied for selecting the best operating conditions for lowering a combination of multi-responses such as chemical oxygen demand (COD), total organic carbon (TOC), total phenols and turbidity. From the analysis, the 600 mg/L coagulant dosage appears to be top ranked, which obtained a higher grey relational grade. The implementation of statistical techniques in OMW treatment can enhance the efficiency of this process, which in turn supports the preparation of waste streams for further purification processes in a sustainable way.
In this study, a synthetic phenol solution of water and raw olive mill wastewater (OMW) were considered to achieve purification of the aqueous streams from pollutants. Only OMW was initially ...submitted to a coagulation/flocculation process, to reduce the turbidity, phenols, and chemical oxygen demand (COD). This first treatment appeared to be mandatory in order to remove solids from wastewater, allowing the successive use of laboratory-made core-shell nanocomposites. In detail, the optimal coagulant concentration, i.e., chitosan, was 500 mg/L, allowing a reduction of the turbidity and the COD value by 90% and 33%, respectively. After this, phenol wastewater was tested for photocatalysis and then OMW was treated by employing the laboratory-made nanocomposites in a photoreactor equipped with visible light sources and using optimal catalyst concentrations, which allowed for an additional 45% reduction of the COD of the OMW. In addition to this, the effect of the operating temperature was investigated on the photocatalytic process, and suitable kinetic models proposed.
The interest in producing copper nanoparticles is high, mainly due to their enhanced properties, a wide range of possible and different applications, and the possibility for their use in the ...framework of catalysis. The purpose of this study is to synthesize copper nanoparticles by chemical reduction of copper sulfate with L-ascorbic acid and sodium borohydride capable to eliminate free radicals providing an antioxidant environment promoting pure copper nuclei formation. The micromixing conditions necessary for the nanoparticles production are provided by a spinning disk reactor (SDR). Relevant operational parameters, such as the disk speed velocity and the position of the reactant injectors, will lead to different product outcomes. The latter was checked by means of a dynamic light scattering instrument (DLS). At the end, depending on the adopted operating conditions, the SDR was able to produce particles between 16 nm and 39 nm, with a particle size distribution (PSD) characterized by a narrow, monomodal plot. In comparison to the smallest particles obtained in a stirred reactor tank, that is, 132 nm, the obtained results appear to be very promising.
According to ISO/TS 80004, a nanomaterial is defined as the “material with any external dimension in the nanoscale or having internal structure or surface structure in the nanoscale”, with nanoscale ...defined as the “length range approximately from 1 nm to 100 nm” ...
Biochar has been used in various applications, e.g., as a soil conditioner and in remediation of contaminated water, wastewater, and gaseous emissions. In the latter application, biochar was shown to ...be a suitable alternative to activated carbon, providing high treatment efficiency. Since biochar is a by-product of waste pyrolysis, its use allows for compliance with circular economics. Thus, this research aims to obtain a detailed characterization of three carbonaceous materials: an activated carbon (CARBOSORB NC 1240®) and two biochars (RE-CHAR® and AMBIOTON®). In particular, the objective of this work is to compare the properties of three carbonaceous materials to evaluate whether the application of the two biochars is the same as that of activated carbon. The characterization included, among others, particle size distribution, elemental analysis, pH, scanning electron microscope, pore volume, specific surface area, and ionic exchange capacity. The results showed that CARBOSORB NC 1240® presented a higher specific surface (1126.64 m2/g) than AMBIOTON® (256.23 m2/g) and RE-CHAR® (280.25 m2/g). Both biochar and activated carbon belong to the category of mesoporous media, showing a pore size between 2 and 50 nm (20–500 Å). Moreover, the chemical composition analysis shows similar C, H, and N composition in the three carbonaceous materials while a higher O composition in RE-CHAR® (9.9%) than in CARBOSORB NC 1240 ® (2.67%) and AMBIOTON® (1.10%). Differences in physical and chemical properties are determined by the feedstock and pyrolysis or gasification temperature. The results obtained allowed to compare the selected materials among each other and with other carbonaceous adsorbents.
In the last decades much effort was put in understanding fouling phenomena on membranes. One successful approach to describe fouling issues on membranes is the critical flux theory. The possibility ...to measure a maximum value of the permeate flux for a given system without incurring in fouling issues was a breakthrough in membrane process design. However, in many cases critical fluxes were found to be very low, lower than the economic feasibility of the process. The knowledge of the critical flux value must be therefore considered as a good starting point for process design. In the last years, a new concept was introduced, the threshold flux, which defines the maximum permeate flow rate characterized by a low constant fouling rate regime. This concept, more than the critical flux, is a new practical tool for membrane process designers. In this paper a brief review on critical and threshold flux will be reported and analyzed. And since the concepts share many common aspects, merged into a new concept, called the boundary flux, the validation will occur by the analysis of previously collected data by the authors, during the treatment of olive vegetation wastewater by ultrafiltration and nanofiltration membranes.
The operation of a spiral-wound nanofiltration membrane module used continuously for three years in order to purify different pretreated olive mill wastewater streams will be discussed. The membrane ...module was for the first time used at the beginning of year 2006 on a batch pilot scale plant for critical flux studies and wastewater treatment in our laboratories.
The olive mill wastewater is a waste stream produced by the olive oil mill factories, characterized by very high organic matter load and polyphenols concentration. Without fouling inhibition at all, nanofiltration membranes will reach zero-flux conditions within days. This is not the case of this nanofiltration membrane module, which was successfully operated continuously for three years during our laboratory work. This result was reached by proper fouling inhibition control, relaying on both critical flux measurements and the development of an optimized operation method. Moreover, supercritical operation experiments were performed on another nanofiltration module of the same model in order to validate the approach.
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