The water hyacinth (Eichhorniacrassipes) was studied as a pollution monitor for accumulation of silver and subsequent recovery of the element from the plant tissues. After cultivation of the plants for 24 hours in silver solution containing 40 mg/l the plants were harvested, rinsed with tap water and dried at 110°C for 48 hours. The dried material was submitted to pyrolysis and chemical digestion and the silver absorbed by the plant was precipitated, calcinated and recovered in the metal form. The average concentration of silver was found to be 8,000 mg g−1 of dried plant material. An Atomic Absorption Spectrophotometer was utilized for the analysis.

The average concentration of silver recovered from the dried plant material, was 70% of the initial silver concentration of the silver solutions and revealed a purity of 98%.

The water hyacinth has the potential of producing 873/ha/day of dried material and can be used for the production of biogas rich in methane (Wolverton, B.C.; McDonald, R.C.).

After the wastewater treatment, the harvested plants can be used for biogas production and the residual sludge may be utilized for recycling the valuable metal.

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