Marina B. Šćiban

Removal of water turbidity by natural coagulants obtained from chestnut and acorn

The ability of seed extracts of several species of chestnut and acorn to act as natural coagulants was tested using a synthetic turbid water. Active components were extracted from ground seeds of Horse chestnut and acorns of some species of family Fagaceae: Common oak, Turkey oak, Northern red oak and European chestnut. All investigated extracts had coagulation capabilities and their amounts depended on pH values and initial turbidities. The seed extracts from European chestnut and Common oak acorn were the most efficient expressing the highest coagulation activities, about 80% and 70%, respectively, in both low and medium investigated water turbidities at the lowest coagulant dose 0.5 ml/L.

Modified hardwood sawdust as adsorbent of heavy metal ions from water

The sawdust of oak and black locust hardwood was found to have good adsorption capacities for heavy metal ions. The leaching of coloured organic matters during the adsorption can be prevented by each of the following pre-treatments of adsorbents: with formaldehyde in acidic medium, with sodium hydroxide solution after formaldehyde treatment, or with sodium hydroxide only. The studies indicated that the leaching of coloured matters from modified hardwood sawdust was less than that from unmodified hardwood sawdust, namely between 70 and 94%, dependent on wood species and the method of modification. At the same time, adsorption capacities of modified adsorbents were higher than unmodified adsorbents when sodium hydroxide was applied for modification. When formaldehyde was applied for modification, the adsorption capacities of adsorbents remained unchanged. Only the application of sodium hydroxide was recommended for modification of hardwood sawdust.

Proteins from common bean (Phaseolus vulgaris) seed as a natural coagulant for potential application in water turbidity removal

The ability of coagulation active proteins from common bean (Phaseolus vulgaris) seed for the removal of water turbidity was studied. Partial purification of protein coagulant was performed by precipitation with ammonium sulphate, dialysis and anion exchange chromatography. Adsorption parameters for ion-exchange process were established using dialysate extract. Results revealed that the highest values of the adsorbed protein were achieved in 50 mmol/L phosphate buffer at pH 7.5 and the maximum adsorption capacity was calculated to be 0.51 mg protein/mL matrix. Partially purified coagulant at initial turbidity 35 NTU expressed the highest value of coagulation activity, 72.3%, which was almost 22 times higher than those obtained by crude extract considering applied dosages. At the same time, the increase in organic matter that remained in water after coagulation with purified protein coagulant was more than 16 times lower than those with crude extract, relatively to its content in blank.

Study of the Adsorption of Copper(II) Ions from Water onto Wood Sawdust, Pulp and Lignin

The adsorption of copper(II) ions from aqueous solution onto sawdusts from different kinds of wood, pulp and Kraft lignin has been studied. The results of batch studies showed that Kraft lignin was a good adsorbent over the whole concentration range studied, hard woods (oak and black locust) were good when the Cu(II) ion concentration in the aqueous solution was high, while soft woods (poplar, willow, fir) and pulp were good for the adsorption of Cu(II) ions when the latter were present over the low concentration range. The maximum adsorption capacities of the adsorbents investigated towards Cu(II) ions were in the 1.77–9.35 mg/g range. Isotherms were used to obtain the corresponding thermodynamic parameters. Almost complete Cu(II) ion desorption was achieved using 0.1 M mineral acid solutions. The regenerated adsorbents could be used in several adsorption/desorption cycles.

Isotherms for the adsorption of Cu(II) onto lignin: Comparison of linear and non-linear methods

Equilibrium studies were carried out for the adsorption of Cu(II) onto Kraft lignin as an adsorbent. The experimental data were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear method. Comparison of linear and non-linear regression method was given in selecting the optimum isotherm for the experimental data. The coefficient of correlation r2 and Chi-square test χ2 was used to select the best linear theoretical isotherm. The best linear model is Redlich-Peterson isotherm model, where r2=0,985 and χ2=0,02. In order to predict the error ERRSQ, HYBRD, MPSD, ARE and EABS were used. Moreover, by minimizing these error functions the optimal values of parameters and also the optimum isotherm was found. The Redlich-Peterson isotherm was found to be the best representative for adsorption of Cu(II) on the adsorbent in the cases when ERRSQ, HYBRD, MPSD functions were used. There coefficients of determination are 0.986, 0.985, 0.984, respectively and Chi-square is 0.02 in all cases. Freundlich isotherms which were obtained by minimization of the ERRSQ, HYBRD, MPSD, ARE and EABS function showed very good agreement with experimental data. In all cases the coefficients of determination are greater than 0.91. Besides, it was observed that non-linear isotherm models were better for representation of equilibrium data than linearized models.

Evaluation of possibility of textile dye removal from wastewater by aqueous two-phase extraction

Abstract Possibility of removal of textile dye from wastewater by extraction in aqueous two-phase system (ATPS) was studied in model solution of Acid blue 9. Partitioning of the dye in ATPSs composed of polyethylene glycol of different molecular weights (1,500, 6,000, and 10,000 g/mol) and several salts (ammonium sulfate, sodium sulfate, and sodium citrate) was investigated. Best results in respect of partitioning coefficient and concentration factor were obtained in polyethylene glycol 1,500/sodium citrate and polyethylene glycol 6,000/sodium citrate systems, respectively. Moreover, in selected ATPSs, the effect of tie-line length and volume ratio on partitioning parameters of Acid blue 9 was evaluated in order to determine conditions at which the highest possible removal of textile dye from wastewater could be achieved.

Application of membrane and natural coagulants for stillage purification

Abstract Wastewater that remains after bioethanol production (stillage) is a major problem from the viewpoint of environmental protection. Besides the large volume, stillage contains high amounts of organic matter, suspended solids, dead yeast cells and their metabolites, so it should not be disposed in the recipient without previous treatment. In this work the possibility of usage of microfiltration for stillage purification was investigated. Also, the application of natural coagulants was investigated, in order to increase the efficiency of microfiltration for stillage treatment. Results obtained after microfiltration showed chemical oxygen demand (COD) reduction of 35% while the combined use of natural coagulants and microfiltration achieved 50% of COD reduction compared to the initial value. Many published works confirmed the activity of natural coagulants on model water but just few of them investigated the activity of natural coagulants in real samples of waters and wastewaters, which makes this pap...

The fractionation of natural coagulant extracted from common bean by use of ultrafiltration membranes

Abstract In the age of rapid degradation of environment, the use of natural coagulants for water and wastewater treatment represents a promising idea which is in line with the global sustainable initiatives. Since these coagulants are of organic nature and have complex composition, it is important to separate components which show coagulation activity from those which do not show. In this work, ultrafiltration membranes with MW cut off of 10,000 Da and 30,000 Da were used for fractionation of natural coagulant extract obtained from common bean seed. Coagulation efficiency of these fractions was assessed by jar tests in model water. Coagulation conditions (pH and applied dose of coagulant) were optimized for each fraction. The fraction of extract with molecular weight lower than 10,000 Da was showed as the best coagulant with coagulation efficiency more than 40% at pH 10 and applied dose 2.5 ml/l.

A new approach for modelling and optimization of Cu(II) biosorption from aqueous solutions using sugar beet shreds in a fixed-bed column

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 mg L-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 SSer (7.8·10-4) and highest R2 (0.9998), 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 mg·L-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.

Characterization of raw and treated sugar beet shreds for copper ions adsorption

AbstractLignocellulosic materials have a great potential to be converted into different high value products including biofuels, value-added chemicals, and cheap energy sources for microbial fermentation and enzyme production. Their multifunctionality and ability to reuse contribute to their great importance in terms of environmental protection and sustainable development. Such materials are sugar beet shreds (SBS) which are usually used as animal feed but since they are produced in large amount in sugar industry, they can also be used as an adsorbent or for bioethanol production. Bioethanol production from SBS includes pretreatment processes in order to remove pectic substances and lignin, followed by enzymatic hydrolysis of cellulose in order to obtain the solution of fermented sugars. A novelty in this work is the investigation if solid residues from the pretreatment process of SBS for bioethanol production can be used as adsorbents, the same as raw SBS. Textural characteristics and capacities for coppe...