Laura 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.

On the retention of uranyl and thorium ions from radioactive solution on peat moss

The efficiency of the radioactive uranyl and thorium ions on the peat moss from aqueous solutions has been investigated under different experimental conditions. The sorption and desorption of uranyl and thorium ions on three types (unmodified peat moss, peat moss treated with HNO(3) and peat moss treated with NaOH) of peat moss were studied by the static method. Peat moss was selected as it is available in nature, in any amount, as a cheap and accessible sorbent. Study on desorption of such ions led to the conclusion that the most favourable desorptive reagent for the uranyl ions is Na(2)CO(3) 1M while, for the thorium ions is HCl 1M. The results obtained show that the parameters here under investigation exercise a significant effect on the sorption process of the two ions. Also, the investigations performed recommend the peat moss treated with a base as a potential sorbent for the uranyl and thorium ions from a radioactive aqueous solution.

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.

Enhancing Biosorption Characteristics of Marine Green Algae (Ulva lactuca)for Heavy Metals Removal by Alkaline Treatment

The biosorption characteristics of alkaline treated marine green algae (Ulva lactuca) have been studied for the removal of Pb(II), Zn(II) and Co(II) from aqueous solution, at room temperature. Batch experiments were performed to examine the effect of NaOH concentration used for treatment, initial heavy metals concentration and contact time, in comparison with untreated algae. The biosorption capacity of alkaline treated marine green algae increases with increasing of NaOH concentration, up to 0.6 mol L-1, when an improvement of biosorption capacity with 11.75% for Pb(II), 60.64% for Zn(II) and 62.53% for Co(II) respectively, was obtained. The Langmuir model provides best correlation of equilibrium experimental data, and the pseudo-second order describes well the biosorption kinetics of considered heavy metals. The heavy metal ions could be easily desorbed from loaded biosorbent, and this may be reuse at least in three biosorption/desorption cycles.

Cd(II) extraction in PEG-based two-phase aqueous systems in the presence of iodide ions. Analysis of PEG-rich solid phases

Cd(II) plus iodide species were extracted into PEG-rich phases in the aqueous PEG(1550)-(NH4)2SO4 system at pH 2.05–7.12. IR spectra show that increasing (NH4)2SO4 solution acidity does not protonate PEG ether oxygen atoms, but decreases water content in the PEG-rich phases. Metallic species’ extraction into the PEG predominantly alters how water molecules bind to polymer chains; the changes in their absorption bands depend on pH. Microscopy shows that “fixation” of the extracted metal in the PEG-rich phase occurs by specific interactions which depend on the species. These also determine changes in the polymer chains’ conformation.

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.

Optimization of process parameters for heavy metals biosorption onto mustard waste biomass

Abstract Mustard waste biomass was tested as a biosorbent for the removal of Pb(II), Zn(II) and Cd(II) from aqueous solution. This strategy may be a sustainable option for the utilization of such wastes. The influence of the most important operating parameters of the biosorption process was analyzed in batch experiments, and optimal conditions were found to include initial solution pH 5.5, 5.0 g biosorbent/L, 2 hours of contact time and high temperature. Kinetics analyses show that the maximum of biosorption was quickly reached and could be described by a pseudo-second order kinetic model. The equilibrium data were well fitted by the Langmuir model, and the highest values of maximum biosorption capacity were obtained with Pb(II), followed by Zn(II) and Cd(II). The thermodynamic parameters of the biosorption process (ΔG, ΔH and ΔS) were also evaluated from isotherms. The results of this study suggest that mustard waste biomass can be used for the removal of heavy metals from aqueous media.