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In this study, a cost-effective calcium alginate-based ion-exchange resin (CABIER) was employed for treatment of metal waste streams. pH, concentration, and presence of competitive metal ions played important roles in the removal. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the functional groups on the carbohydrate backbone (i.e., C−O−R and COO-1) were responsible for the binding of metals. It was found that the lead abstraction was driven by the ion exchange between Ca2+ and Pb2+. On the contrary, the Cu2+ ion was stripped via both ion exchange with Ca2+ and coordination of the other functional groups. A new mathematical model based on ion exchange (between metal and calcium) and elementary coordination (among metals and functional groups) reactions successfully described and predicted the metal removal under various conditions (e.g., pH, concentration, and existence of competitive metal ions). It was found from the modeling that metal binding follows a decreasing order of Pb2+ > Cu2+ > Ca2+.

SummaryArbuscular mycorrhizal (AM) symbiosis is known to stimulate plant drought tolerance. However, the molecular basis for the direct involvement of AM fungi (AMF) in plant water relations has not been established.Two full-length aquaporin genes, namely GintAQPF1 and GintAQPF2, were cloned by rapid amplification of cDNA 5′-and 3′-ends from an AMF, Glomus intraradices. Aquaporin localization, activities and water permeability were examined by heterologous expression in yeast. Gene expression during symbiosis was also analyzed by quantitative real-time polymerase chain reaction.GintAQPF1 was localized to the plasma membrane of yeast, whereas GintAQPF2 was localized to both plasma and intracellular membranes. Transformed yeast cells exhibited a significant decrease in cell volume on hyperosmotic shock and faster protoplast bursting on hypoosmotic shock. Polyethylene glycol (PEG) stimulated, but glycerol inhibited, the aquaporin activities. Furthermore, the expression of the two genes in arbuscule-enriched cortical cells and extraradical mycelia of maize roots was also enhanced significantly under drought stress.GintAQPF1 and GintAQPF2 are the first two functional aquaporin genes from AMF reported to date. Our data strongly support potential water transport via AMF to host plants, which leads to a better understanding of the important role of AMF in plant drought tolerance.

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