Małgorzata Kuczajowska-Zadrożna

Kinetics of desorption of heavy metals and their mixtures from immobilized activated sludge

AbstractIn order to use biosurfactants to desorb metals from biosorbents without changing their adsorption capacity, there is a need to determine conditions of process. In this study, we examined the kinetics of desorption of cadmium, zinc, and copper and their mixtures from activated sludge immobilized in 1.5% sodium alginate with 0.5% polyvinyl alcohol. Metals leaching from immobilized biomass were analyzed with the use of three biosurfactants—saponin, JBR 515, JBR 425, and nitric acid. Desorption effectiveness of single metals and their mixtures was also investigated as influenced by different desorption parameters such as pH, contact time, and dose of desorbents. The obtained values of kinetic constants of pseudo-first-order (k1) and pseudo-second-order (k2) showed that in case of all analyzed desorbents, the process of metals leaching from immobilized activated sludge proceeded according to the pseudo-second-order reaction as indicated by the R2 values. Out of the analyzed desorbents, saponin and nit...

The use of cross-linked chitosan beads for nutrients (nitrate and orthophosphate) removal from a mixture of P-PO4, N-NO2 and N-NO3

A hydrogel chitosan sorbent ionically cross-linked with sodium citrate and covalently cross-linked with epichlorohydrin was used to remove nutrients from an equimolar mixture of P-PO4, N-NO2 and N-NO3. The scope of the study included, among other things, determination of the influence of pH on nutrient sorption effectiveness, nutrient sorption kinetics as well as determination of the maximum sorption capacity of cross-linked chitosan sorbents regarding P-PO4 (H2PO4-, HPO42-), N-NO2 (HNO2, NO2-), and N-NO3 (NO3-). The effect of the type of the cross-linking agent on the affinity of the modified chitosan to each nutrient was studied as well. The kinetics of nutrient sorption on the tested chitosan sorbents was best described with the pseudo-second order model. The model of intramolecular diffusion showed that P-PO4, N-NO2 and N-NO3 sorption on cross-linked hydrogel chitosan beads proceeded in two phases. The best sorbent of nutrients turned out to be chitosan cross-linked covalently with epichlorohydrin; with P-PO4, N-NO2 and N-NO3 sorption capacity reaching: 1.23, 0.94 and 0.76mmol/g, respectively (total of 2.92mmol/g). For comparison, the sorption capacity of chitosan cross-linked ionically with sodium citrate was: 0.43, 0.39 and 0.39mmol/g for P-PO4, N-NO2 and N-NO3, respectively (total of 1.21mmol/g).

Application of biosurfactants for heavy netals leaching from immobilized activated sludge / Zastosowanie biosurfaktantów do wymywania metali ciężkich z immobilizowanego osadu czynnego

Abstract This study was undertaken to determine the effectiveness of biosurfactants - saponin, tannin and rhamnolipids JBR 515 and 425, for the removal of cadmium, zinc and copper from activated sludge immobilized in 1.5% sodium alginate with 0.5% polyvinyl alcohol. We also established the impact of pH value on biosorbent regeneration with the analyzed biosurfactants and determined the critical micelle concentration (CMC) in solutions containing the biosorbent and biosurfactant and in exact samples with heavy metals. Saponin exhibited the highest effectiveness of metals leaching at pH 1-5, and rhamnosides at pH 5-6. In addition, the study demonstrated a significant effect of the ratio of biosorbent mass to washing agent volume (m/V) on the effectiveness of metals leaching. Of the biosurfactants analyzed, saponin was ca. 100% effective in leaching zinc and copper. The effectiveness of the other biosurfactants was lower and depended on the metal being leached W pracy podjęto badania nad określeniem efektywności wykorzystania biosurfaktantów - saponiny, taniny oraz ramnolipidów JBR 515 i JBR 425 do wymywania kadmu, cynku i miedzi z osadu czynnego immobilizowanego w alginianie sodu 1,5% z alkoholem poliwinylowym 0,5%. Przeprowadzone badania pozwoliły określić wpływ odczynu na regenerację biosorbentu za pomocą testowanych biosurfaktantów, wyznaczyć krytyczne stężenie micelarne (CMC) w roztworach zawierających biosorbent i biosurfaktant oraz w próbach właściwych z metalami ciężkimi. Saponina charakteryzowała się najwyższą efektywnością wymywania metali przy pH 1-5, a ramnolipidy przy pH 5-6. Ponadto badania wykazały istotny wpływ stosunku masy biosorbentu do objętości eluatu (m/V) na skuteczność wymywania metali. Spośród analizowanych biosurfaktantów saponina wykazywała około 100% efektywność usuwania z biosorbentu cynku i miedzi. Skuteczność innych biosurfaktantów była niższa i zależała od rodzaju metalu

Phosphate removal from aqueous solutions by chitin and chitosan in flakes

The article presents the effectiveness of phosphate adsorption on the flakes of chitin and chitosan. Studies performed determined adsorption capacity of chitin and chitosan, best among the tested adsorption pH and the equilibrium time. Langmuir model was used to describe the results. The highest removal efficiency of phosphorus compounds using chitin was obtained at pH 3 and with chitosan at pH 4. The study of phosphate equilibrium concentration time obtained for both sorbents was carried out at three concentrations of 1, 5 and 10 mg/dm. The highest sorption efficiency of the phosphate using chitin was achieved after 20 minutes of the process and at the chitosan after 40 minutes. In the case of chitosan after the equilibrium time the effect of partial P-PO4 release was observed, which could be related to the change in pH of the solution by the sorbent. Studies have shown that chitosan is a more effective absorbent for phosphorus compounds. The maximum adsorption capacity of chitosan with phosphate was 6.65 mg/g, and chitin 2.09 mg/g.

Effect of conditions of air-lift type reactor work on cadmium adsorption

We investigated cadmium sorption by activated sludge immobilized in 1.5% sodium alginate with 0.5% polyvinyl alcohol. Experiments were conducted in an air-lift type reactor at the constant concentration of biosorbent reaching 5 d.m./dm3, at three flow rates: 0.1, 0.25 and 0.5 V/h, and at three concentrations of the inflowing cadmium solution: 10, 25 and 50mg/dm3. Analyses determined adsorption capacity of activated sludge immobilized in alginate as well as reactor’s work time depending on flow rate and initial concentration of the solution. Results achieved were described with the use of Thomas model. The highest adsorption capacity of the sorbent (determined from the Thomas model), i.e., 200.2 mg/g d.m. was obtained at inflowing solution concentration of 50 mg/dm3 and flow rate of 0.1 V/h, whereas the lowest one reached 53.69 mg/g d.m. at the respective values of 10 mg/dm3 and 0.1 V/h. Analyses were also carried out to determine the degree of biosorbent adsorption capacity utilization at the assumed effectiveness of cadmium removal — at the breakthrough point (C=0.05*C0) and at adsorption capacity depletion point (C-0.9*C0). The study demonstrated that the effectiveness of adsorption capacity utilization was influenced by both the concentration and flow rate of the inflowing solution. The highest degree of sorbent capacity utilization was noted at inflowing solution concentration of 50 mg/dm3 and flow rate of 0.1 V/h, whereas the lowest one at the respective values of 10 mg/dm3 and 0.1 V/h. The course of the process under dynamic conditions was evaluated using coefficients of tangent inclination — a, at point C/C0=½. A distinct tendency was demonstrated in changes of tangent slope a as affected by the initial concentration of cadmium and flow rate of the solution. The highest values of a coefficient were achieved at the flow rate of 0.1 V/h and initial cadmium concentration of 50 mg/dm3.

Cyclical metal adsorption and desorption through sludge immobilized in chitosan media

In this research, a cyclical adsorption/desorption of cadmium and zinc from solutions containing a single metal or its mixture in ratio of 1:1 and 1:2 using immobilized activated sludge in the chitosan (ASC) was examined. In the adsorption studies, the optimal dose of ASC was 4 g/L. The highest desorption efficiency was achieved for 1M HNO3. Both adsorption and desorption occurred in accordance with a pseudo-second order reactions which is confirmed by R values. Mass of zinc adsorbed and desorbed in one cycle from a solution containing a single metal was 0.78 and 0.40 mmol/g d.w. when cadmium was lower (respectively 0.41 and 0.21 mmol/g d.w.). In subsequent cycles, both metals were adsorbed and desorbed at a lower efficiency. The highest efficiency of desorption was observed for a mixture of Cd:Zn in the ratio of 1:1 and 1:2, respectively 86% and 89% of cycle1, whereas for the zinc it was 70% and 53%. Desorption efficiency of both metals and its mixtures, in subsequent cycles gradually decreased.

USE OF SAWDUST IMMOBILISED ON CHITOSAN FOR DISPOSAL OF DYES FROM WATER SOLUTIONS

In this article, the sorption properties of chitosan hydrogel beads, beech sawdust and sawdust immobilised on chitosan in relation to Reactive Black 5 (RB5) and Basic Violet 10 (BV10) dyes were compared. In the conducted research, the sorption capacities of the sorbents, sorption pH and the point of zero charge (pHZPC) were determined. For the description of the obtained results, the double Langmuir model has been used. The highest effectiveness of the cationic and anionic dye removal on chitosan hydrogel beads and sawdust immobilised on chitosan was obtained at pH 4, whereas on sawdust, the pH was 3. The best sorbent in relation to the RB5 dye was obtained using chitosan hydrogel beads, and in relation to BV10, it was sawdust. The maximum sorption capacity of chitosan in relation to RB5 was 875.66 mg/g, whereas the sorption capacity of sawdust in relation to BV10 was 30.15 mg/g. The research has shown that the sorbent in the form of sawdust immobilised on chitosan had a high sorption capacity in relation to anionic as well as cationic dyes. Immobilisation of sawdust on chitosan led to the creation of a universal sorbent in relation to cationic and anionic dyes.

IMPACT OF CHITOSAN CROSS-LINKING ON RB 5 DYE ADSORPTION EFFICIENCY

In this work, the effect of cross-linking of chitosan beads on the removal efficiency of dye RB 5 from aqueous solutions was defined. In the studies not crosslinked chitosan as well as chitosan cross-linked with a chemical cross-linking agent glutaraldehyde and ionic cross-linking agent pentasodium tripolyphosphate were used. The scope of the research included the determination of pH at which the adsorption process proceeded efficiently, study time, in order to designate the time, after which the reaction equilibrium is reached and to determine the kinetics of the adsorption process and constants in the Langmuir 2 equation. The work sets maximum sorption capacity of the sorbent non-crosslinked and two crosslinked sorbents. Based on these results, it was found that the highest removal efficiency of dye RB 5 was obtained for chitosan crosslinked with ion agent pentasodium tripolyphosphate. The maximum sorption capacity of the sorbent amounted 1125.7 mg / g d.m. of chitosan.

THE INFLUENCE OF CHITOSAN DEACETYLATION DEGREE ON REACTIVE BLACK 5 SORPTION EFFICIENCY FROM AQUEOUS SOLUTIONS

In the paper sorption capacity of chitosan having a deacetylation degree DD=75%, DD=85% and DD=90% relatively to the Reactive Black 5 were compared. Studies on the effectiveness of the dye sorption were carried out in a wide pH range – from 3 to 11. For each of the tested chitosan sorbents, sorption capacity has been determined. The results were described by isotherms Freundlich and Lagmuir isotherms, and a double Langmuir isotherm. Sorption of Reactive Black 5 most efficiently occurred at pH 4. At pH <4 chitosan sorbents underwent dissolution, regardless of the degree of deacetylation. The efficiency of dye sorption increased with the degree of deacetylation. The sorption capacity calculated after 12 h of the chitosan sorption with DD=75%, DD=85% and DD =90% was, relatively to the Reactive Black 5, respectively 433.03 mg/g and 464.52 mg/g and 532.14 mg/g. The impact of the deacetylation degree on pHZPC (zero point of charge) of the sorbent was also examined. Along with the increase in the deacetylation degree the value of chitosan pHZPC increased as well and at DD=75% DD=85% and DD=90%, pHZPC amounted respectively 7.6, 7.7 and 7.8.