New method for evaluation of heavy metal binding to alginate beads using pH and conductivity data

Abstract

Extensive research has been conducted for removal and recovery of heavy metals from wastewater and industrial wastewater in recent years. Due to its low cost and high sorption efficiency, alginate was extensively investigated as a biosorbent. It is known that the sorption of metals to alginate is rate limited. However, the sampling in the beginning of experiments, from 30 seconds to few minutes, is very difficult, if not impossible. In this study, a nontraditional experimental method was used to determine the removal kinetics of metals for short time periods. A relationship among pH, conductivity, and metal concentration was established. It was shown that the sorption mechanism was ion exchange for all metals investigated in this study. A series of experiments was conducted to determine the ion exchange kinetics of different metals at varying pH conditions. Second order pseudo rate kinetics was shown to define the experimental findings well. Results also showed that the extent of exchange significantly reduced as the pH decreased. The selectivity of metal exchange to alginate beads was determined. It was observed that the extent of the ion exchange was greatest for Cu 2+ and lowest for Mn 2+ and Fe 2+ , following the order of Cu 2+ > Zn 2+ ∼ = Co 2+ ∼ = Ni 2+ > Mn 2+ ∼ = Fe 2+ .

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

“…This applies more to the DW_PM system, where a positive correlation was found between the amount of adsorbed metal ions and the amount of released iron ions. Studies on the relationship between the physical parameters of various metal ions, including toxic metal ions, and the binding affinity of these metal ions for alginate, have shown that Pb 2+ , Cd 2+ , Cu 2+ and Zn 2+ have higher affinity to alginates in comparison to Fe 3+ [ 47 , 48 ]. In the DW_PM solution, the ionic exchange between metal ions and Fe 3+ was four times greater than in the SW_PM solution, which is indicated by a much greater amount of released Fe 3+ ions in the DW_PM solution.…”

Copper and nitrophenol pollutants removal by Na-montmorillonite/alginate microcapsules

“…Encapsulation unfavoured the sorption since the highest rate constants were observed for Namont. A double mechanism of diffusion in the gel structure and ion exchange was proposed to describe the kinetic of sorption of metals [18,19,24].…”

Preparation of p-tert[(dimethylamino)methyl]-calix[4]arene functionalized aminopropylpolysiloxane resin for selective solid-phase extraction and preconcentration of metal ions

“…We found the pH value of the solutions changed from 3.0 to 2.24 for Cr (III) and 2.19 for Ni (II), and from 4.0 to 3.11 for Cu (II), 3.20 for Co (II) and 3.14 for Zn (II), respectively. These results indicated that the mechanism probably involves the competitive adsorption of H + with metal ions for the exchange site in the system [34,35]. In order to ensure quantitative adsorption and avoid precipitation at higher pH values, pH 4.0 was chosen as the optimum pH for further studies.…”