JOURNAL OF CHEMISTS, TECHNOLOGISTS AND ENVIRONMENTALISTS

Conditioning of waste sludge from biological wastewater treatment plant from gikil

2023-05-09T14:37:38+02:00

Sludge generated in wastewater treatment processes must be treated in an adequate manner, and therefore disposed of in an environmentally friendly manner. The biggest obstacle to the efficient use of sludge is the high water content, therefore the development of methods to accelerate the sludge dewatering process is particularly important. For the purposes of the research, the waste sludge created in the process of purifying ammoniaphenol wastewater in the GIKIL factory was used. Sludge conditioning was performed by adding a commercial flocculant (0.1 % solution) in combination with pyrophyllite, kaolin clay and shredded cardboard. According to earlier research, the volume of waste sludge with the addition of a suitable flocculant could be reduced by more than 5 times compared to the initial amount, leaving behind a large amount of separated water that can be returned to the process. The results show that the addition of commercial flocculant in the amount of 0.8 % gives the best results (reduction of sludge volume by 78.8 %). A lower percentage was found in samples with a mixture of flocculants with pyrophyllite (78 %) and kaolin (77.6 %), while the combination of flocculants with waste cardboard was ineffective (64.4 %). Addition of flocculant to waste sludge resulted in a decrease in specific filtration resistance (1.15x107 s2/g). A decrease in specific resistance was also observed in flocculant/kaolin clay (0.8x107 s2/g) and flocculant/cardboard (1.09x107 s2/g) samples. Sludge conditioning also resulted in a reduction of suspended solids in the neonate compared to settled raw sludge without additives.

Effect of incorporation of the plant extracts in natural casing on the color of fermented sausages

2023-05-09T14:20:00+02:00

In this study, the effect of incorporation of the plant extracts in a natural casing on the color and sensory attributes in fermented sausages, “sucuk” type, was evaluated. The sausages were produced in industrial conditions, stuffed into the pretreated natural casings, vacuum packaged, and stored at 4˚C for six months. Five groups of sausages were tested, C1 (natural casing without treatment), C2 (treated with 6% (v/v) ethanol), C3 (treated with ascorbic acid), A (treated with ethanol extract of Aronia melanocarpa), and D (treated with ethanol extract of Cornus mas). Based on the results, it was concluded that the use of Aronia extract had an effect on the color of the surface. During storage, there was an increase in lightness (L*) and the proportion of red color (a*), and also a slight increase in the proportion of yellow color (b*). There were no major changes in the color parameters on the cross-section of the sausage. Sensory testing of the sausage samples found that there was no difference between the tested samples in terms of external appearance, while the results of the "different from control" - DFC test showed that the A sample was visually more acceptable and had a nicer surface color.

Synthesis and investigation of 1,8-naphthalimide derivative with sensor activity

2023-05-09T13:59:55+02:00

The paper reports on the synthesis and fluorescence characteristics of novel 1,8-naphthalimide fluorophore. It was configured as a “fluorophore-spacerreceptor” system able to act as a pH-probe via PET (photoinduced electron transfer) fluorescence sensing mechanism. Due to the tertiary amine receptor the novel probe showed “off-on” switching properties under the transition from alkaline to acid media. Also, the ability of the probe to detect metal ions in water/ dimethylformamide (1:1, v/v) has been evaluated by monitoring the changes of its fluorescence intensity. Among the tested metal ions (Cu2+, Pb2+, Zn2+, Ni2+, Hg2+, Fe3+) only the presence of Fe3+ was efficiently detected by fluorescence quenching mechanism.

Influence of substrate roughness on print quality parameters of digitally printed paper substrates

2023-06-14T12:12:48+02:00

In addition to printing techniques, there are various characteristics that
affect the quality of printed products. Most frequently questioned features
are line, dot, and text reproduction. In this paper it is investigated how
different substrates, printed by the same printing technique, affect the quality
parameters of printed samples. Print quality includes the process of obtaining
the desired reproductions of color and image elements, important parameters
of print quality are the quality of lines and dots, and the feature of the substrate
that is significant for this work is the roughness of the substrate. This paper
presents the testing of three different materials on to which the test form
was printed by electrophotography, as a digital printing technique. The tests
are based on analysis of line, dot and text reproduction, as well as analysis
of the roughness of the substrate on samples printed in black. Based on the
obtained results it can be concluded that the substrate affects the quality of
printed products.

Analysis of arsenic monitoring in underground water of the Republic of Serbia for 2018-2020

2023-05-09T14:30:06+02:00

Arsenic is a heavy metalloid that occurs frequently in nature. The most serious repercussions for human health occur when it is found in drinking water (It can harm the circulatory, pulmonary, and nervous systems, as well as cause skin and other organs cancer). This paper presents the values of arsenic concentration in the Republic of Serbia's groundwater from 2018 to 2020, based on lab tests completed by the Serbian Environmental Protection Agency. Bearing in mind the fact that the Decree on Limit Values of Pollutants in Surface and Groundwater and Sediment and Deadlines for Reaching Them (Official Gazette of RS No. 50/12) does not prescribe limit values for arsenic in groundwater, as well as the fact that 75% of drinking water is supplied from groundwater, the results of testing the concentration of arsenic in groundwater are compared with the maximum allowed concentration of arsenic in drinking water prescribed by the Ordinance on the Hygiene of Drinking Water (Official Gazette of the FRY No. 42/98 and 44/99, Official Gazette RS No. 28/19). The concentrations of arsenic in eight piezometers were found to be above the maximum allowed concentration limit for drinking water for all three years. Having in mind the stated facts, it is necessary to update the regulations of the Republic of Serbia concerning the limit values of pollutants in groundwater, and to include the limit values for arsenic in it. The amendment of the regulation requires more detailed research regarding the concentration and origin of arsenic in groundwater.

Pretreatment of biomass pellets by acid washing in order to reduce alkaline components

2023-05-09T14:11:27+02:00

Due to the limited availability of wood, as the highest quality raw material for the production of biomass pellets, increasing attention is being paid to the production and use of pellets from low-quality materials such as different types of agricultural waste. However, the complex chemical composition of these types of biomass often leads to various problems during their combustion. One of the biggest problems when it comes to burning biomass pellets is related to the low melting temperature of the resulting ash and its tendency to sintering. By modifying the chemical composition of biomass, it is possible to influence the method of combustion and the characteristics of residual ash. Modification of biomass composition can be carried out by chemical pretreatment with acids, which reduces the concentration of alkali metals and alleviates ash adhesion and the tendency to form slag. Pellets made from wood biomass, soy straw and chamomile waste from the process of processing medicinal plants were used for the tests in this work. Chemical pretreatment, which consisted in washing the pellet samples with a diluted solution of hydrochloric acid, resulted in mass loss in all cases. The amount of ash, after treatment in hydrochloric acid solution, was reduced by 72.15% - 93.27%, depending on the concentration of acid and the type of biomass.

Effect of neutralization degree of methacrylic acid on hydrogel swelling and drug release

2023-05-09T13:45:34+02:00

Drug delivery system is an amazing tool which is widely used for drug protection and its controlled release in order to enhance drug bioavailability, reduce side effects and therefore to improve overall therapy. Hydrogels have been attracted great attention as drug carriers due to their great physicochemical properties, similarity to the living tissues and biocompatibility. One group of pH sensitive hydrogels are based on poly(methacrylic acid) (PMAA). These non-toxic hydrogels are used as drug delivery system because they swell as a response to the change in pH of external environment and drug is being released during the process. In present study, in order to improve the control of drug release rate, caffeine was encapsulated in liposomes which were further embedded into PMC hydrogel (PMCL). It was investigated how the change in neutralization degree of methacrylic acid affect the swelling degree of PMCL hydrogels and caffeine release in two environments at 37 °C for 24 h: 0.1 M hydrochloride acid (pH 1) and phosphate buffer with pH value of 6.8 (pH 6.8), as a simulation of pH environment in human stomach and intestines, respectively. Obtained results show that PMCL hydrogels have great potential for controlled release of poorly water-soluble drugs in human intestines.