Competitive Interaction of Phosphate with Selected Toxic Metals Ions in the Adsorption from Effluent of Sewage Sludge by Iron/Alginate Beads.

Wastewater is characterized by a high content of phosphate and toxic metals. Many studies have confirmed the sorption affinity of alginate adsorbents for these ions. In this study, the adsorption of phosphate from effluent of sewage sludge on biodegradable alginate matrices cross-linked with Fe3+ ions (Fe_Alg) was investigated. Kinetics and adsorption isotherms were tested in laboratory conditions in deionized water (DW_P) and in the effluent (SW_P), and in the same solutions enriched in toxic metals ions-Cu2+, Cd2+, Pb2+, and Zn2+ (DW_PM and SW_PM). Batch experiments were performed by changing the concentration of phosphate at constant metal concentration. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data for both metals and phosphate. The Freundlich equation provided the best fit with the experimental results of phosphate adsorption from DW_P and DW_PM, while the adsorption from SD_P and SD_PM was better described by the Langmuir equation. For tested systems, the affinity of the Fe_Alg for metal ions was in the following decreasing order: Pb2+ > Cu2+ > Cd2+ > Zn2+ in DW_PM, and Pb2+ > Cu2+ > Cd2+ > Zn2+ in SW_PM. The metals' enrichment of the DW_P solution increased the affinity of Fe_Alg beads relating to phosphate, while the addition of the metals of the SW_P solution decreased this affinity.

Influence of Formulation on Mobility of Clomazone in Soil.

The mobility of clomazone [2-(2-chlorobenzylo)-4,4-dimetylo-1,2-oxazolidin-3-one] in a loamy sand soil and a sand soil was studied in a soil column under laboratory conditions. Commercial clomazone formulation (Command 480 EC) and clomazone immobilized in an alginate matrix were used for a leaching experiment. For both formulations, the same dose of 2.0 mg of the active substance was applied. After an application of a herbicide, the columns were irrigated with: 100, 40 and 3.7 mm of water. After 1 h, when an addition of water was completed, the soils were sampled in the 5 cm segments and were used for the analysis of the residues. The use of an alginate formulation reduced the vertical mobility of clomazone into a soil layer in comparison with the formulation EC.

Removal of Phosphate from Aqueous Solution Using Alginate/Iron (III) Chloride Capsules: a Laboratory Study.

Binding phosphate at participation of alginate/FeCl3 capsules was studied with laboratory experiments. The hydrogel microcapsules were obtained with the dropping-in method, by gelation of sodium alginate water solution by iron (III) chloride solution. Phosphate adsorption characteristics were studied in a static batch system with respect to changes in contact time, initial phosphates concentration, pH of solution, and temperature. After 24 h of the tests, average 87.5% of phosphate ions were removed from the natural water solutions; after 48 h, an equilibrium was reached. The adsorption data were well fit by the Freundlich isotherm model. Parameter k of the isotherms amounted from 43.4 to 104.7, whereas parameter n amounted from 0.362 to 0.476. The course of processes of phosphate adsorption and iron desorption to aquatic phase, as well as changes in pH, suggests that phosphate adsorption is a major mechanism of phosphate removal, whereas simultaneously, but at a much lower degree, a process of precipitation of phosphate by iron (III) ions released from the capsules to the solution takes its place. Parameters calculated in the Freundlich isotherm equation show that by using several times smaller amounts of iron, it is possible to remove similar or bigger amounts of phosphorus than with other adsorbents containing iron. The alginate/FeCl3 adsorbent removes phosphate in a wide pH spectrum-from 4 to 10. Results suggest that the proposed adsorbent has potential in remediation of contaminated waters by phosphate.

Electrochemical study on the adsorption of carbon oxides and oxidation of their adsorption products on platinum group metals and alloys.

CO(2) reduction and CO adsorption on noble metals (Pt, Rh, Pd) and their alloys (Pt-Rh, Pd-Pt, Pd-Rh, Pd-Pt-Rh) prepared as thin rough deposits have been studied by chronoamperometry (CA), cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). The influence of alloy surface composition on the values of surface coverage, eps (electron per site) and potential of the oxidation of CO(2) reduction and CO adsorption products is shown. The oxidation of the adsorbate on Pt-Rh alloys proceeds more easily (at lower potentials) than on pure metals. On the other hand, in the case of Pd-Pt and Pd-Rh alloys the adsorbate oxidation is more difficult and requires higher potentials than on Pt or Rh. The analysis of the EQCM signal is presented for the case of adsorption and oxidation of carbon oxide adsorption products on the electrodes studied. The comparison of adsorption parameters and the EQCM response obtained for platinum group metals and alloys leads to the conclusion that reduced CO(2) cannot be totally identified with adsorbed CO.