Effect of Na₂SiO₃ on heavy metal uptake by field grown <em>Basella alba</em> L. in Matara, Sri Lanka

Abstract

Abstract. In this study, we investigated heavy metal uptake and the effects of Na 2 SiO 3 on heavy metal absorption by field grown Basella alba L (Basellaceae). The concentrations of Fe, Cr, Pb and Cd in the field soils were 29755.30 ± 292.02, 32.99 ± 0.97, 26.01 ± 1.02, 0.13 ± 0.004 µg/g, respectively. These concentrations are significantly below the maximum permissible limits reported by FAO/WHO. Although Fe, Cr, Pb and Cd were present in the soil, only Fe was absorbed by B. alba; the tissue concentrations of other heavy metals were below the detection limit. The distribution of Fe from soil to different plant parts was investigated by calculating transfer factors. Low transfer factors indicated low absorption and translocation of Fe from soil to plant tissue. We also investigated the effects of Na 2 SiO 3 on metal absorption by applying two different concentrations of Na 2 SiO 3 (Si-100 mg/L and Si-50 mg/L) alongside a control. There was a significant reduction of Fe absorption in B. alba treated with Si-100mg/L of Na 2 SiO 3 compared to that of plants treated with Si-50 mg/L of Na 2 SiO 3 and the control.

Experimental Study on the Removal of NO from Coal-Fired Flue Gas by the Na2SiO3/Fenton System

“…When the pH > 10, free Fe ions were almost nonexistent, and Fe was mainly present in the form of dispersed fine hydrous oxide or hydroxide colloidal particles . At pH = 9.4–12.6, the hydrolysis product of Na 2 SiO 3 was the negatively charged SiO­(OH) 3 – , which had an obvious micelle structure and could not only adsorb but also effectively passivate the positively charged metal oxides and hydroxides, thus forming a stable colloidal solution . We can find that the solution after the reaction was a uniform red-brown liquid, and an obvious bright pathway appeared under laser irradiation, which indicated that the reaction solution was colloidal.…”

“…23 At pH = 9.4−12.6, the hydrolysis product of Na 2 SiO 3 was the negatively charged SiO(OH) 3 − , 24 which had an obvious micelle structure and could not only adsorb but also effectively passivate the positively charged metal oxides and hydroxides, thus forming a stable colloidal solution. 25 We can find that the solution after the reaction was a uniform red-brown liquid, and an obvious bright pathway appeared under laser irradiation, which indicated that the reaction solution was colloidal. Therefore, it was presumed that a heterogeneous surface-catalyzed reaction initiated by the colloidal state of Fe occurred during the reaction.…”