[Show abstract][Hide abstract] ABSTRACT: Salvinia possess inherent capacity to accumulate high levels of various heavy metals. Accumulation of Cr, Fe, Ni, Cu, Pb and Cd ranged between 6 and 9 mg g(-1)dry wt., while accumulation of Co, Zn and Mn was ∼4 mg g(-1)dry wt. Heavy metal accumulation affected the physiological status of plants. Photosystem II activity noted to decline in Ni, Co, Cd, Pb, Zn and Cu exposed plants, while Photosystem I activity showed enhancement under heavy metal stress in comparison to control. The increase in PS I activity supported build up of transthylakoidal proton gradient (ΔpH), which subsequently helped in maintaining the photophosphorylation potential. Ribulose 1,5 dicarboxylase/oxygenase (Rubisco) activity noted a decline. Alterations in photosynthetic potential of Salvinia result primarily from changes in carbon assimilation efficiency with slight variations in primary photochemical activities and photophosphorylation potential. Studies suggest that Salvinia possess efficient photosynthetic machinery to withstand heavy metal stress.
[Show abstract][Hide abstract] ABSTRACT: Batch adsorption experiments were performed to study adsorption potential of agricultural residues viz. rice straw, wheat straw and Salvinia plant biomass for removal of heavy metals such as Cr, Ni, and Cd. Plant materials were used in different combinations. Heavy metal removal efficiency was more at low metal concentration (35 mg/L). Salvinia biomass possessed higher efficiency for removing heavy metals such as Cr, Ni and Cd followed by a combination where three materials (rice straw, wheat straw, Salvinia biomass) were taken together in comparison to other combinations. The adsorption data fitted in Langmuir and Freundlich isotherm models.The present investigations revealed that agricultural residues such as rice straw and wheat straw along with Salvinia biomass can serve as low-cost alternative for removal of heavy metals from wastewaters. INTRODUCTION Heavy metal released during different industrial and mining processes pose threat to living organisms, there-fore it becomes important to develop technologies that result in effective removal of heavy metals from waste-waters. Various methods for heavy metal removal in-cluding chemical precipitation, membrane process, ion exchange, liquid extraction and electrodialysis are non-economical and have many disadvantages such as high reagent and energy requirements, generation of toxic sludge or other waste products that require disposal or treatment (Demirbas, 2008). In contrast, adsorption tech-nique can has been proved to be an excellent method to treat industrial waste effluents, offering significant advantages like low-cost, availability, profitability, easy operation and efficiency (Li et al., 2007). Biosorption of heavy metals from aqueous solutions is a relatively new process that has proven very promising in the removal of contaminants from aqueous effluents. In recent years, various natural adsorbents such as agri-cultural wastes including sunflower stalks, Eucalyp-tus bark, maize bran, coconut shell, waste tea, rice straw, tree leaves, peanut and walnut husks have been tried to achieve effective removal of various heavy metals (Sun and Shi, 1998; Karthikeyan et al., 2005; Sarin and Pant, 2006; Singh et al., 2006; Hashem et al., 2007; Demirbas, 2008; Kahraman et al. 2008; Nameni et al., 2008).