Modelling and optimization of continuousbiosorption of heavy metal ions from water

U disertaciji je ispitana mogucnost korišcenja izluženih rezanaca šecerne repe za adsorpciju jona bakra u koloni sa nepokretnim slojem. Eksperimenti su izvedeni primenom Boks-Benkenovog eksperimentalnog dizajna na tri nivoa sa tri promenljive: koncentracija napojnog rastvora (50-150 mgL-1), masa adsorbenta (8-12 g) i pH napojnog rastvora (4,0-5,0). Dobijene prevojne krive su fitovane uobicajenim empirijskim modelima, Boart-Adamsovim i modelom doza-odziv. Na osnovu uocene asimetrije prevojne krive, predložen je novi matematicki model. Novi model predlaže prevojnu krivu koja se sastoji od dva dela, koji u zbiru daju kumulativnu krivu koja dosledno pokriva uocenu asimetriju. Uzimajuci u obzir najnižu prosecnu sumu kvadrata odstupanja, SSer (3,610-3) i najvišu prosecnu vrednost koeficijenta determinacije, R2 (0,9989), novi model je pokazao najbolje fitovanje eksperimentalnih podataka, u poreenju sa uobicajeno korišcenim modelima adsorpcije u koloni. RSM i ANN modelovanje je dalje korišceno za evaluaciju procesnih parametara i optimizaciju procesa. Najznacajnija nezavisno promenljiva velicina, koja ispoljava negativan uticaj na odabrani odziv (kriticno vreme), bila je koncentracija napojnog rastvora, dok je masa adsorbenta ispoljila slabiji i pozitivan uticaj na odziv. Optimizacijom procesa metodom ANN je utvreno da se najveca vrednost kriticnog vremena (341,4 min) postiže pri sledecim uslovima: C0=50 mgL-1, ma=12 g and pH 4,53, dok metoda RSM smatra pH vrednost faktorom koji nema znacaja po odziv u ispitivanom opsegu, i postiže maksimalno kriticno vreme od 314,8 min, pri istim ostalim uslovima kao i ANN. Iskorišceni adsorbent, zasicen jonima bakra, je zatim spaljen i dobijeni pepeo je iskorišcen kao punilo u proizvodnji gume. Proizvedena su cetiri uzorka gume sa razlicitim sadržajem pepela. Pracen je proces vulkanizacije gume, odreena su mehanicka svojstva gotovog proizvoda i izvreno je poreenje dobijenih rezultata izmeu uzoraka sa i bez dodatka pepela. Rezultati su pokazali da dodatak pepela u strukturu gume ne utice znacajno na njene mehanicke osobine. Meutim, povecanje sadržaja pepela u gumi dovodi do povecanja energije aktivacije procesa vulkanizacije, što se može smatrati unapreenjem procesa proizvodnje gume u slucaju proizvoda velikih dimenzija. Na kraju, ispitano je izluživanje bakra iz gotovih proizvoda od gume. Rezultti su pokazali da je kolicina bakra izluženog u vodu veoma niska, reda velicine 0,001%, što se može smatrati zanemarljivim.The potential use of sugar beet shreds for copper ions removal from aqueous solution in a fixed-bed column was investigated. Experiments were performed using Box-Behnken experimental design on three levels and three variables: concentration of the inlet solution (50-150 mgL-1), adsorbent dosage (8-12 g) and pH of the inlet solution (4.0-5.0). The obtained breakthrough curves were fitted with two common empirical models, Bohart-Adams and dose-response. Observing the asymmetric shape of the breakthrough curves, the new mathematical model was proposed. The new model proposes the breakthrough curve composed of two parts, sum of which gives the asymmetrical S-shaped curve, accurately matching experimental data. Regarding the lowest average SSer (3.610-3) and highest average R2 (0.9989), new model exhibited the best fit comparing to the commonly used models. RSM and ANN modelling were employed for process variables evaluation and optimization. The most influential parameter exhibiting negative influence on target response (critical time) was concentration of the inlet solution, while the adsorbent dosage exhibited positive influence. Optimization procedure revealed that the highest critical time (341.4 min) was achieved at following conditions: C0=50 mgL-1, ma=12 g and pH 4.53 by ANN, while RSM considered pH as insignificant factor and obtained 314.8 min as the highest response. Discarded adsorbent, saturated with copper ions, was then incinerated and the obtained ash was used as a rubber filler. Four rubber samples containing different amounts of added ash were produced. The vulcanization process was monitored and mechanical properties was measured and compared with the samples with no ash added. The results revealed that addition of ash has no significant effect on the rubber mechanical properties. However, as the ash content increases, the activation energy of the vulcanization process increases too, which can be considered as an improvement in the cases of large-dimensioned rubber products production. Finally, the leaching of the copper from rubber products was investigated. Results showed that very small amount of copper, order of magnitude 0,001%, were leached from the rubber into the water, which can be considered as insignificant

Modelling and optimization of continuousbiosorption of heavy metal ions from water

U disertaciji je ispitana mogucnost korišcenja izluženih rezanaca šecerne repe za adsorpciju jona bakra u koloni sa nepokretnim slojem. Eksperimenti su izvedeni primenom Boks-Benkenovog eksperimentalnog dizajna na tri nivoa sa tri promenljive: koncentracija napojnog rastvora (50-150 mgL-1), masa adsorbenta (8-12 g) i pH napojnog rastvora (4,0-5,0). Dobijene prevojne krive su fitovane uobicajenim empirijskim modelima, Boart-Adamsovim i modelom doza-odziv. Na osnovu uocene asimetrije prevojne krive, predložen je novi matematicki model. Novi model predlaže prevojnu krivu koja se sastoji od dva dela, koji u zbiru daju kumulativnu krivu koja dosledno pokriva uocenu asimetriju. Uzimajuci u obzir najnižu prosecnu sumu kvadrata odstupanja, SSer (3,610-3) i najvišu prosecnu vrednost koeficijenta determinacije, R2 (0,9989), novi model je pokazao najbolje fitovanje eksperimentalnih podataka, u poreenju sa uobicajeno korišcenim modelima adsorpcije u koloni. RSM i ANN modelovanje je dalje korišceno za evaluaciju procesnih parametara i optimizaciju procesa. Najznacajnija nezavisno promenljiva velicina, koja ispoljava negativan uticaj na odabrani odziv (kriticno vreme), bila je koncentracija napojnog rastvora, dok je masa adsorbenta ispoljila slabiji i pozitivan uticaj na odziv. Optimizacijom procesa metodom ANN je utvreno da se najveca vrednost kriticnog vremena (341,4 min) postiže pri sledecim uslovima: C0=50 mgL-1, ma=12 g and pH 4,53, dok metoda RSM smatra pH vrednost faktorom koji nema znacaja po odziv u ispitivanom opsegu, i postiže maksimalno kriticno vreme od 314,8 min, pri istim ostalim uslovima kao i ANN. Iskorišceni adsorbent, zasicen jonima bakra, je zatim spaljen i dobijeni pepeo je iskorišcen kao punilo u proizvodnji gume. Proizvedena su cetiri uzorka gume sa razlicitim sadržajem pepela. Pracen je proces vulkanizacije gume, odreena su mehanicka svojstva gotovog proizvoda i izvreno je poreenje dobijenih rezultata izmeu uzoraka sa i bez dodatka pepela. Rezultati su pokazali da dodatak pepela u strukturu gume ne utice znacajno na njene mehanicke osobine. Meutim, povecanje sadržaja pepela u gumi dovodi do povecanja energije aktivacije procesa vulkanizacije, što se može smatrati unapreenjem procesa proizvodnje gume u slucaju proizvoda velikih dimenzija. Na kraju, ispitano je izluživanje bakra iz gotovih proizvoda od gume. Rezultti su pokazali da je kolicina bakra izluženog u vodu veoma niska, reda velicine 0,001%, što se može smatrati zanemarljivim.The potential use of sugar beet shreds for copper ions removal from aqueous solution in a fixed-bed column was investigated. Experiments were performed using Box-Behnken experimental design on three levels and three variables: concentration of the inlet solution (50-150 mgL-1), adsorbent dosage (8-12 g) and pH of the inlet solution (4.0-5.0). The obtained breakthrough curves were fitted with two common empirical models, Bohart-Adams and dose-response. Observing the asymmetric shape of the breakthrough curves, the new mathematical model was proposed. The new model proposes the breakthrough curve composed of two parts, sum of which gives the asymmetrical S-shaped curve, accurately matching experimental data. Regarding the lowest average SSer (3.610-3) and highest average R2 (0.9989), new model exhibited the best fit comparing to the commonly used models. RSM and ANN modelling were employed for process variables evaluation and optimization. The most influential parameter exhibiting negative influence on target response (critical time) was concentration of the inlet solution, while the adsorbent dosage exhibited positive influence. Optimization procedure revealed that the highest critical time (341.4 min) was achieved at following conditions: C0=50 mgL-1, ma=12 g and pH 4.53 by ANN, while RSM considered pH as insignificant factor and obtained 314.8 min as the highest response. Discarded adsorbent, saturated with copper ions, was then incinerated and the obtained ash was used as a rubber filler. Four rubber samples containing different amounts of added ash were produced. The vulcanization process was monitored and mechanical properties was measured and compared with the samples with no ash added. The results revealed that addition of ash has no significant effect on the rubber mechanical properties. However, as the ash content increases, the activation energy of the vulcanization process increases too, which can be considered as an improvement in the cases of large-dimensioned rubber products production. Finally, the leaching of the copper from rubber products was investigated. Results showed that very small amount of copper, order of magnitude 0,001%, were leached from the rubber into the water, which can be considered as insignificant

Air mycopopulations in Petrovská klobása producing facility

Different types of filamentous fungi periodically cause problems in small-scale facilities for traditional dry fermented sausages, such as Petrovská klobása from Vojvodina province (Serbia). Mould contamination can be observed during processing, ripening, and storage. Sausages may become spoiled due to visible mould colonies on the surface and off-flavours they produce. The most important - if mycotoxin production occurs it might promote a number of health disorders. Knowledge and control of filamentous fungi are, therefore, essential to produce sausages that satisfy the criteria of hygienic quality, sensorial characteristics, and food safety. The aim of this study was to survey mycoflora of a small-scale facility producing traditional dry fermented sausage - Petrovská klobása. The mould contamination of the air in processing unit and ripening chambers was investigated, in order to determine the important fungi in terms of spoilage of the products and ability to produce mycotoxins. The mould contamination of air in processing unit and ripening chambers examined was in range 0.22 - 1.89 log CFU/P.d. Isolated moulds belong to 6 genera: Aspergillus (3 species), Cladosporium (1 species), Eurotium (2 species), Fusarium (1 species), Penicillium (12 species) and Scopulariopsis (1 species). The most abundant were species of Penicillium genus, many of which are capable for mycotoxin production. The level and diversity of fungal contamination of air varied between samples, influenced by the general hygiene, the buildings, the airflow, the outdoor environments, and the time of year. This knowledge is crucial for the improvement of hygiene control systems in small-scale processing units

Results of mycological and mycotoxicological investigations of corn-based feed for dairy cow diet

In this study, fungal contamination was determined as well as total aflatoxin B1(AB1), ochratoxin A (OTA) and zearalenon (ZEA) levels in corn-based feed samples obtained from four different farms in Serbia (n=35) during one year. Mycotoxins were detected in feed using the VICAM fluorometric method. It was determined that 97.14% of all samples were contaminated with moulds which belonged to following genera: Absidia, Acremonium, Aspergillus, Cladosporium, Geotrichum, Eurotium, Fusarium, Mucor, Mortierella, Oidiodendron, Penicillium, Rhizopus, Scopulariopsis, Syncephalastrum, Trichoderma, Ulocladium and Wallrothiella. A total of 58 different species were identified. Total mould count per 1 g ranged from 1.00 log cfu/g (dried corn silage - autumn, fresh corn silage - summer and corn grain silage - spring) to 7.32 log cfu/g (dried corn silage - winter). Mycotoxins were isolated from 28.5% of samples: ZEA was found in summer (220-240 μg/kg) and in spring (240 μg/kg) in concentrate samples; OTA was detected in winter in dried corn silage (16 μg/kg) and in spring (12 μg/kg); all samples were AB1 free

Kserofilne mikopopulacije izolovane iz semena uljane repice

This paper presents the results of an investigation related to mycological populations of rapeseed samples produced in the Institute of Field and Vegetable Crops in Novi Sad (location: Rimski Šančevi, Novi Sad), with a special emphasis on the potentially toxigenic mycopopulations. Mycological investigations were performed on the samples that were treated with 4% solution of Na-hypochlorite, and on the ones that were not submitted to this treatment. Isolation and determination of total mould count was carried out using Dichloran Glycerol Agar (DG18). The identification of isolated moulds was done according to modern keys for fungal determination. From 20 untreated tested samples, 17 were contaminated with moulds (10.0 to 4.7x102 cfu/g). When the samples were treated with 4% solution of Na-hypochlorite, moulds were isolated only form 4 samples, and the total mould count ranged from 10.0 to 60.0 cfu/g. In the isolated mycopopulations, xerophilic moulds dominated, especially those from the genera Aspergillus, Eurotium and Penicillium. In the isolated mycopopulations, high degree of isolated species belonged to toxigenic species from the genera Alternaria, Aspergillus, Fusarium, Eurotium and Penicillium.U radu su data istraživanja vezana za mikološku populaciju u uzorcima uljane repice proizvedene u Institutu za ratarstvo i povrtarstvo (lokacija Rimski Šančevi, Novi Sad), sa posebnim osvrtom na potencijalno toksigenu mikopopulaciju. Mikološka ispitivanja su izvedena u uzorcima koji su tretirani sa Na-hipohloritom, kao i u uzorcima koji nisu podvrgnuti ovom tretmanu. Izolacija i određivanje ukupnog broja plesni izvedeno je na Dixloran Glicerol agaru. Identifikacija izolovanih vrsta plesni izvedena je prema ključevima za determinaciju koji su opisani u literaturi. Od 20 ispitanih uzoraka u 17 je utvrđeno prisustvo plesni i ukupan broj se kretao do 10 do 4,7x102 cfu/g. Kada su uzorci tretirani 4% rastvorom Na-hipohlorita plesni su izolovane iz 4 uzorka, a ukupni broj plesni se kretao od 10,0 do 60,0 cfu/g. U izolovanoj mikopopulaciji dominirale su kserofilne vrste iz rodova Aspergillus, Eurotium i Penicillium. Izolovanu mikopopulaciju u visokom procentu činile se potencijalne toksigene vrste iz rodova Alternaria, Aspergillus, Fusarium, Eurotium i Penicillium

Optimization of microfiltration for distillery wastewater purification

In our previous work we examined the possibility of application of microfiltration for distillery stillage purification in the systems without [1] and with the presence of static mixer [2]. Feed flow rate (Q = 40; 100 and 160 l/h ), transmembrane pressure (TMP = 0.3; 0.6 and 0.9 bar) and feed pH (3; 6 and 9) were considered for design of experiments. Influence of choosen factors on permeate flux and specific energy consumption was investigated using Response Surface Methodology. The results showed that Response Surface Methodology is an appropriate model for mathematical presentation of the process. To optimize a process that has two or more responses, several methods can be applied, but the most commonly used method is the concept of the desired function (desirability function) [3]. In this work optimization of the experimental conditions was conducted using the modified Harrington method of the desired function. To optimize the microfiltration process of distillery wastewater, the following responses were selected: mean flux permeate in the static mixer system (JSM) and the relative change in specific energy consumption (ER). The goal of optimization was to select the feed flow rate and transmembrane pressure values for which the observed responses will be maximum, ie their desired functions will have a higher value. Obtained results (Figure 1) showed that the microfiltration was best performed at maximum flow and transmembrane pressure values, at all pH values, with the fact that the value of total desired function decreases with the increase of pH. If all factors, including pH value, are used for optimization, the optimum values of the parameters for optimization showed that the microfiltration was best performed at the values of feed flow of 160 l/h and TMP of 0.9 bar, at pH value of 5.81. Under these conditions, the total desired function had a maximum value of 0.944, the mean permeate flux for the system with static mixer was 58.3 l/m 3 h, while the relative change in the specific energy consumption was 123%

The process of obtaining quartz sand size fraction -0.4 + 0.05 mm for use in water glass production

The paper presents the process of quartz sand processing from the „Bijela Stijena“-Skočić deposit in the plant „Kesogradnja d.o.o.“ at Kozluk near Zvornik, Republic of Srpska. Bearing in mind the fact that this quartz sand is used for water glass production in the company „Birač“ - Zvornik or „Alumina“ Zvornik, it was necessary to meet the quality requirements prescribed by that industrial production. Thus, the required size was -0.4+0.05 mm and the Fe2O3 content was maximum of 0.04%. Based on the laboratory tests, a technological scheme for the quartz raw material valorization was conceived in the separation of the company „Kesogradnja d.o.o.“. The obtained results showed that quartz sand for water glass size fraction -0.4+0.05 mm could be obtained in the plant. Also, by introducing a magnetic concentration after washing and grading, the Fe2O3 content was reduced from 0.131% as it is in the initial sample to 0.038% which meets the required conditions from the water glass producers

Removal of copper ions from aqueous solutions by sugar beet shreds and poplar sawdust in a fixed-bed column

The potential use of sugar beet shreds and poplar sawdust for copper ions removal from aqueous solution in a fixed-bed column was investigated. Experiments were performed in a glass column (inner diameter 2.204 cm and length 50 cm), in the down-flow mode with a flow rate set to approximately 12 mL/min. Concentration (C0) and the pH of the inlet solution were 100 mg/L and 4.5, respectively, and 10 g of the adsorbent were used to form a bed of nearly 19 cm in length. Sugar beet shreds and poplar sawdust were milled and sieved through the set of sieves, and the fraction of 400 to 600 μm was used for the adsorption experiments. The consecutive aliquots of 50 to 150 mL were collected at the bottom of the column, and they were analyzed for the content of the Cu(II) ions (C), according to the standard method of complexometric titration [1]. The column adsorption process is described regarding the effluent concentration-volume profile, or the breakthrough curve, obtained from the plot of Ct/C0 versus volume of the effluent. The shape of the curve gives an insight into the dynamic behavior of the process [2, 3]. Various mathematical models can be used to describe fixed-bed adsorption [4, 5]. In this research, the novel two-stage approach for the breakthrough curve modelling was applied. The fit quality, expressed as coefficient of determination (R2 ) and the sum of squared errors (SSer), showed that this model fits the experimental data more accurately than any other commonly used one-stage model. Namely, R2 and SSer for sugar beet shreds were 0.9984 and 9.69·10-3 , respectively, while for the poplar sawdust they were 0.9999 and 2.87·10-4 , respectively. The characteristic value that describes this two-stage phenomenon is moiety of each stage, p. In the case of sugar beet shreds it was 0.43, while for the poplar sawdust it was 0.85. These results suggest that the adsorption of the copper ions onto examined biosorbents occurs under multiple mechanisms, occurring simultaneously but shifting in the dominance. When using sugar beet shreds as an adsorbent, these mechanisms are nearly equal in their dominance (0.43 to 0.57). In the case of the poplar sawdust one mechanism is significantly more dominant then other (0.85 to 0.15), and the misuse of onestage models is usual and more likely. However, the extensive mathematical and statistical analysis confirmed the validity of the two-stage modelling approach for the copper biosorption onto sugar beet shreds and poplar sawdust