Arsenic(V) Removal from Water by Resin Impregnated with Cyclodextrin Ligand

Crosslinked Polydiallyldimethylammonium Chloride Adsorbent for the Selective Separation of Rhenium Ions from Pregnant Leach Solutions

The depletion of valuable mineral reserves has rendered effluents generated from mining and industrial processing activities a promising resource for the production of precious elements. The synthesis and improvement of new adsorbents to extract valuable compounds from industrial wastes and pregnant leach solutions, besides increasing wealth, can play a significant role in reducing environmental concerns. In this work, a new and low-cost adsorbent for the selective extraction of rhenium (perrhenate ions, ReO4-) was synthesized by the free-radical polymerization (FRP) of a diallyl dimethylammonium chloride monomer (quaternary amine) in the presence of a crosslinker. Various methods were employed to characterize the polymeric adsorbent. The results revealed that the designed polymeric adsorbent had a high surface area and pores with nano-metric dimensions and a pore volume of 6.4 × 10-3 cm3/g. Four environments-single, binary, multicomponent, and real solutions-were applied to evaluate the adsorbent's performance in the selective separation of Re. Additionally, these environments were used to understand the behavior of molybdenum ions, the primary competitors of perrhenate ions in the ion exchange process. In competitive conditions, using variations in qe,mix/qe, an antagonism phenomenon (qe,mix/qe < 1) occurred due to the inhibitory effect of surface-adsorbed molybdenum ions on the binding of the perrhenate ions. However, across all conditions, the separation values for Re were higher than those for the other studied elements (Mo, Cu, Fe).

A novel multifunctional β-cyclodextrin polymer as a promising sorbent for rapid removal of methylene blue from aqueous solutions

Production wastewater has evolved with dye and printing technology to become one of the major sources of soil and water contamination. The majority of dyes are carcinogenic, teratogenic, and mutagenic compounds. As a result, dealing with the dye in the wastewater is a critical issue. Insoluble polymers of β-cyclodextrin (β-CD), an inexpensive, sustainably produced macrocycle of glucose, have potential to remove dyes from water/wastewater via sorption due to formation of well-defined host-guest complexes. A novel polymeric sorbent based on cyclodextrin was successfully synthesized in a one-step reaction with few reagents. The polymer is characterized by multifunctionality and cross-linked network structure. The sorption studies aimed at the removal of methylene blue (MB) from aqueous solutions. The dominant model was Langmuir isotherm which indicated a sorption capacity of 96.15 mg/g. The rapid removal has already been obtained after 1 min, around 84 % of efficiency. The molecular mechanism of MB sorption by poly(β-CD-BPDA) network is found mostly on the electrostatic interactions and partially on the inclusion of complexation inside supramolecular pores based on cyclodextrins' cavities, hydrogen bonding and slightly π-stacking. The presented polymer seems to be a promising sorbent for the removal of hazardous organic pollutants from water/wastewater.

Determination of some heavy metals from aqueous solutions using modified Amberlite XAD-4 resin by selective solid-phase extraction

The adsorption efficiency of Pb(II) and Cd(II) from aqueous solutions on m-phenylenediamine-modified Amberlite XAD-4 resin was investigated. The effects of pH, adsorbent amount, initial metal concentration, eluent type and volume and flow rate on the retention of the metal ions have been studied on column studies. The optimum parameters were determined as pH 5, concentration 10 mg/L, stirring time 30 min and 0.2 g adsorbent amount and flow rate 2.5 mL/min for a quantitative adsorption. Sorption data were interpreted in terms of Langmuir and Freundlich equations, and both models were found to be fully appropriate. Each column can be used up to 10 sequential analyses without considerable change. The results indicate high metal adsorption capacity and satisfactory recovery of Pb(II) and Cd(II).