Dumitru Bulgariu

Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass.

The biosorption of Pb(II), Cd(II), and Co(II), respectively, from aqueous solution on green algae waste biomass was investigated. The green algae waste biomass was obtained from marine green algae after extraction of oil, and was used as low-cost biosorbent. Batch shaking experiments were performed to examine the effects of initial solution pH, contact time and temperature. The equilibrium biosorption data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetics models (pseudo-first order and pseudo-second order). The results indicate that Langmuir model provide best correlation of experimental data, and the pseudo-second order kinetic equation could best describe the biosorption kinetics of considered heavy metals.

Extraction of metal ions in aqueous polyethylene glycol-inorganic salt two-phase systems in the presence of inorganic extractants: correlation between extraction behaviour and stability constants of extracted species.

The use of aqueous polyethylene glycol-inorganic salt two-phase systems for the extraction of metal ions has a great potential due to their durability, non-toxicity and relative low cost. The aqueous phases can be easily separated by centrifugation, and the operation is possible in a range of experimental conditions. The experimental results have shown that for a given aqueous two-phase system, the extraction behaviour of metal ions in presence of inorganic extractants is mainly dependent on the stability of extracted species. In this paper we review our results obtained at metal ion extraction using inorganic extractants and discuss three major types of extraction behaviours.

Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column.

Sorption of Pb(II) was studied by using a biosorbent mixture of algae waste biomass and Purolite A-100 resin in a packed-bed column. Mixing these two components was done to prevent the clogging of the column and to ensure adequate flow rates. Increasing of solution flow rate and initial Pb(II) concentration make that the breakthrough and saturation points to be attained earlier. The experimental breakthrough curves were modeled using Bohart-Adams, Thomas and Yoon-Nelson models, and the parameters for all these models were calculated. A regeneration efficiency of 98% was achieved using 0.1 mol L(-1) HCl and not significant changes in lead uptake capacity after three biosorption/desorption cycles were noted. The biosorbent mixture was able to remove Pb(II) from synthetic wastewater at pH 5.0 and flow rate of 3.5 mL min(-1), and the obtained effluent has better quality characteristics. The biosorbent mixture it is suitable for a continuous system for large-scale applications.

Adsorption potential of mercury(II) from aqueous solutions onto Romanian peat moss

This study was undertaken to evaluate the adsorption potential of Romanian peat moss for the removal of mercury(II) from aqueous solutions. The batch system experiments carried out showed that this natural material was effective in removing mercury(II). The analysis of FT-IR spectra indicated that the mechanism involved in the adsorption can be mainly attributed to the binding of mercury(II) with the carboxylic groups of Romanian peat moss. Adsorption equilibrium approached within 60 min. The adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity (qmax) was 98.94 mg g−1. Pseudo–second-order kinetic model was applicable to the adsorption data. The thermodynamic parameters indicate that the adsorption process was spontaneous as the Gibbs free energy values were found to be negative (between −17.58 and −27.25 kJ mol−1) at the temperature range of 6–54°C.

Adsorptive Performances of Alkaline Treated Peat for Heavy Metal Removal

The adsorptive performances of alkaline treated peat have been investigated for the removal of Pb(II), Co(II), and Ni(II) ions from aqueous solutions. The influence of initial metal ions concentration and equilibrium contact time was studied in a series of batch experiments, in comparison with natural peat. An increasing of adsorption capacity of alkaline treated peat was obtained for all studied heavy metals (23.07% - Pb(II), 23.53% - Co(II), and 26.19% - Ni(II)). The Langmuir isotherm model was the best model for the mathematical description of studied heavy metals adsorption on alkaline treated peat. A significant decrease of equilibrium contact time in case of alkaline treated peat was also found. The kinetics of Pb(II), Co(II), and Ni(II) uptake by alkaline treated peat followed the pseudo-second order mechanism. The FT-IR spectrometry analysis showed that carboxylic (-COO-) and hydroxyl (-OH) groups play an important role in the heavy metals binding process. The heavy metal could by easily eluted from the loaded adsorbent with 0.1 mol/L HCl and the adsorbent may be reused in several adsorption/desorption cycles. The alkaline treated peat has better adsorption characteristics for the removal of heavy metals from aqueous solutions, and the cost of this treatment is very low.

Adsorption of Lead(II) Ions from Aqueous Solution onto Lignin

The adsorption of lead(II) ions from aqueous solution onto lignin was investigated in this study. Thus, the influence of the initial solution pH, the lignin dosage, the initial Pb(II) ion concentration and the contact time were investigated at room temperature (19 ± 0.5 °C) in a batch system. Adsorption equilibrium was approached within 30 min. The adsorption kinetic data could be well described by the pseudo-second-order kinetic model, while the equilibrium data were well fitted using the Langmuir isotherm model. A maximum adsorption capacity of 32.36 mg/g was observed. The results of this study indicate that lignin has the potential to become an effective and economical adsorbent for the removal of Pb(II) ions from industrial wastewaters.

Characteristics of sorption of uncomplexed and complexed Pb(II) from aqueous solutions onto peat

Batch experiments aimed at the sorption of Pb(II) onto peat were performed from an aqueous solution in both the absence and presence of common complexing agents (acetate or citrate). The influence of the initial pH of the solution, metal ion concentration and contact time on the sorption efficiency of Pb(II) was examined at ambient temperature (18 ± 0.5) °C for each experiment. The results showed that the presence of acetate improved the efficiency of the sorption process, while the presence of citrate in the aqueous solution decreased the efficiency of the Pb(II) sorption onto peat. The equilibrium data fitted well with the Langmuir isotherm model and confirmed the monolayer sorption of uncomplexed and complexed Pb(II) species onto peat. The values of maximum sorption capacities (qmax) were 135.13 mg g−1 for Pb(II) complexed with acetate, q > 79.36 mg g−1 for uncomplexed Pb, q > 38.46 mg g−1 for Pb(II) complexed with citrate. The kinetics of Pb(II) sorption onto peat, in both the absence and presence of complexing agents, indicated a pseudosecond order mechanism. Analysis of IR spectra showed that carboxylic and hydroxyl groups had an important role in the binding process of Pb(II) species onto peat.

Removal of Zn(II) ions from aqueous media on thermal activated sawdust

AbstractThe adsorptive characteristics of thermal activated sawdust were examined for the removal of Zn(II) ions from aqueous solution. Batch experiments were performed in order to study the influence of initial Zn(II) concentration and contact time under optimal experimental conditions (initial solution pH of 1.09 and 6.23, 8.0xa0g/l) and the results were compared with those obtained on non-activated sawdust. A significant increase in adsorption capacity of thermal activated sawdust for Zn(II) ions, with 77.19% at pH 1.09 and with 395.12% at pH 6.23, was obtained at highest Zn(II) initial concentration of 78.50xa0mg/L. The equilibrium data of Zn(II) adsorption onto non-activated sawdust are very well described by the Langmuir model, while in case of Zn(II) adsorption onto thermal activated sawdust, the Freundlich model is more suitable for the fitting of experimental data. From kinetic point of view, the Zn(II) adsorption on thermal activated and non-activated sawdust attains the maximum after 60xa0min of cont...

Valorisation of romanian peat for the removal of some heavy metals from aqueous media

AbstractIn this study, the sorption of some potential toxic heavy metal ions (Pb(II), Hg(II) and Cd(II), respectively) onto Romanian peat was investigated as a function of initial solution pH, sorbent dose, initial metal ions concentration and contact time, at room temperature (20u2009±u20090.5°C), in batch system. The uptake capacity of tested heavy metals decreased by decreasing the initial solution pH, suggesting that competition exists between hydrogen ions, present in high concentration in strong acid media and metal ions. The experimental data were evaluated using Langmuir and Freundlich isotherm models. The isotherm data followed the Langmuir model, and the maximum sorption capacity increases in the order Cd(II)u2009<u2009Pb(II)u2009<u2009Hg(II). The kinetics of metal ions sorption was rather rapid, with at least 68% of sorption occurring in 30u2009min. The experimental data were satisfactory correlated with pseudo-second-order kinetic model, which means that in the sorption mechanism the chemical interaction between positive...

Valorisation possibilities of exhausted biosorbents loaded with metal ions – A review

Biosorption is considered one of the most promising methods for removal of metal ions from aqueous effluents, due to its low-cost and eco-friendly characteristics. However, the exhausted biosorbents loaded with metal ions, obtained at the end of biosorption processes, are still a problem which should be solved to increase the applicability of biosorption on an industrial scale. In this study are examined three possibilities for the valorisation of exhausted biosorbents loaded with metal ions, namely: (i) regeneration and reuse of biosorbents in multiple biosorption cycles, (ii) the use of exhausted biosorbents as fertilizers for soils poor in essential microelements, and (iii) the pyrolysis of exhausted biosorbents, under well defined conditions. The main advantages and disadvantages of each valorisation possibility are reviewed in order to find the best way to use these cheap materials in accordance with the principles of the circular economy and thereby contributing to the development of sustainable biosorption technology.