State of the art in additive manufacturing and its possible chemical and particle hazards—review

Additive manufacturing, enabling rapid prototyping and so-called on-demand production, has become a common method of creating parts or whole devices. On a 3D printer, real objects are produced layer by layer, thus creating extraordinary possibilities as to the number of applications for this type of devices. The opportunities offered by this technique seem to be pushing new boundaries when it comes to both the use of 3D printing in practice and new materials from which the 3D objects can be printed. However, the question arises whether, at the same time, this solution is safe enough to be used without limitations, wherever and by everyone. According to the scientific reports, three-dimensional printing can pose a threat to the user, not only in terms of physical or mechanical hazards, but also through the potential emissions of chemical substances and fine particles. Thus, the presented publication collects information on the additive manufacturing, different techniques, and ways of printing with application of diverse raw materials. It presents an overview of the last 5 years’ publications focusing on 3D printing, especially regarding the potential chemical and particle emission resulting from the use of such printers in both the working environment and private spaces.     

Bulk nanocomposite made of ZnO lamellae embedded in the ZnWO4 matrix: growth from the melt

Journal of Materials Science - Zinc oxide (ZnO) nanostructures exhibiting high exciton binding energy and efficient radiative recombination, even at the room temperature, are of increasing interest...     

Ozonation of Polycyclic Aromatic Hydrocarbons in Water Solution

The degradation of three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BAP), chrysene (CHR), and fluorene (FLU) in aqueous solution using ozone was investigated. The influence of pH of the reaction mixture, ozone concentration, and the presence of a radical scavenger on the reaction rate was determined. The highest rate of PAHs disappearance was achieved in acidic solutions. The radical scavenger, tert-butanol, effectively inhibited the rate of PAHs destruction. The rate constants of direct reaction of PAHs with ozone were calculated and they were equal to (3.32 ± 0.21) × 10⁴; (1.10 ± 0.15) × 10⁴ and 44.8 ± 1.1 M^?1s^?1 for BAP, CHR, and FLU, respectively. The contributions of direct ozonolysis, and radical reaction to PAHs oxidation in ozonation processes, were evaluated.     

Determination of Sodium Dodecyl Sulfate by Means of Photometric Titration with o‐Toluidine Blue Dye

A convenient technique for the determination of sodium dodecyl sulfate is titration with a metachromatic dye using in situ absorbance measurements. A suitable color reagent is ortho‐Toluidine Blue dye. Commercially available immersion optical probe Optrode® possesses a working wavelength of 640 nm, well matching the dye spectrum. The surfactant concentration is linearly related to the titrant volume at a certain solution absorbance. Optimal values of end point absorbance fall in the range from 0.7 to 2. The lower limit of quantitation is equal to 29 mg L^?1. The highest concentration determined in this study was 52 g L^?1. The required determination range may be adjusted by the appropriate selection of analyte volume and titrant concentration. The developed method is intended for routine process control in the surfactant industry. This method needs minimal manual efforts due to the lack of the dilution stage. Application of an automatic titrator looks to be a suitable solution for any industrial lab.     

Microwave-assisted synthesis of anion-exchange resins for sorption of noble metals: how to boost sorption capacity using a proper reaction environment

In the present studies a series of anion-exchange resins was synthesized in a microwave field. The 1,6-diaminohexane functionalized resins were obtained in presence of selected organic solvents, N,N-dimethyl formamide, dimethyl sulfoxide and 1-methyl-2-pyrrolidone. The resins were employed in batch and dynamic processes of Au(III), Pt(IV) and Pd(II) sorption from tricomponent systems in 0.1 M HCl. The experiment was designed in a way that allowed to determine the use of a specific solvent in the microwave field and how it impacts on properties of the anion exchangers. An influence of a reaction environment was discussed taking into account i.e., dielectric characteristics of the specific solvent, efficiency of the syntheses processes as well as the maximum sorption capacity of the resins. Ultimately the application of a specific reaction environment was set together with sorption of noble metals ability and evaluated using infrared spectroscopy. The proceeded analyzes allowed to determine which organic solvent from the selected ones is the most suitable for microwave-assisted synthesis of the anion-exchange resins.     

Effects of various roasting conditions on acrylamide,acrolein, and polycyclic aromatic hydrocarbons content in cocoa bean and the derived chocolates

The effect of roasting parameters such as the temperature (135 and 150°C) and relative humidity of air (RH of 0.3 and 5.0%) on acrylamide, acrolein, and polycyclic aromatic hydrocarbon (PAH) levels in whole and crushed cocoa beans and chocolates derived from these beans was studied. Acrylamide was identified in all tested samples of roasted cocoa beans, irrespective of process conditions. Its contents in chocolates produced from these beans were similar. The highest acrylamide concentration was found in whole cocoa beans roasted at 135°C and RH of 5.0%. Small amounts of acrolein were present only in the roasted whole cocoa beans while neither the roasted crushed cocoa beans nor chocolates contained this aldehyde. Roasting conditions significantly affected the profile and content of PAHs in whole and crushed cocoa beans and the richest in PAHs were crushed cocoa beans roasted at 150°C and RH of 5.0%. The chocolates obtained in this study contained significantly higher concentrations of PAHs than the roasted cocoa beans used for their production. The results of the study demonstrate that optimization of roasting conditions may reduce levels of all these harmful substances in cocoa beans.     

N,N,N-trimethyl chitosan as an efficient antibacterial agent for polypropylene and polylactide nonwovens

The paper presents a method of depositing N,N,N-trimethyl chitosan (TMC) layers onto polypropylene and polylactide nonwovens. A two-step modification procedure is applied: first, grafting the nonwovens with acrylic acid and next layer-by-layer deposition. Turbidimetric measurements confirm the creation of polycomplexes between grafted poly(acrylic acid) and deposited TMC. The created material structure is evaluated using gravimetric analysis, reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy measurements and pH-metric titration. The modified material exhibits good antibacterial properties against Gram-positive bacteria Staphylococcus aureus.     

Effect of temperature and initial dibutyl sulfide concentration in chloroform on its oxidation rate by ozone

A scheme of dibutyl sulfide (DBS) oxidation with ozone and generation of transitional products was determined in this study. The main identified intermediate product was dibutyl sulfoxide (DBSO), and the main end product of DBS oxidation was dibutyl sulfone (DBSO2). It was determined that for three temperatures: 0, 10 and 20 degrees C there was certain initial DBS concentration for which half-times observed in experimental conditions were equal and independent from temperature. Generation of phosgene and water as by-products was confirmed for the reaction of DBS with ozone in chloroform. Results of the described study allowed to present generalized mechanism of sulfide oxidation with ozone.