Researchers from Singapore have experimented with using Tomato and Apple peels to purify water and have found desirables results that they intend to try with peels of other fruits.
Both experiments showed that the Tomato and Apple peels acted as efficient adsorbents for various contaminants and pollutants in water.
The reason behind the experiments was due to the easily assessed biowaste of both tomato and apple peels from the food processing industries which also being biodegradable would passage for viable and cheaper water purification with minimal use of energy plus less use of chemicals in the purification process therefore favoring the environment as a whole, and benefiting economically disadvantaged communities which would otherwise find difficulty in building a water purification plant due to limited electricity or resources.
Thanks to the biomembrane structure of the tomato peels, and other factors including the pH, nature and amount of adsorbent used in the extraction, toxic metal ions and organic pollutants, including dissolved organic and inorganic chemicals, dyes and pesticides were efficiently removed from water and such could also be applicable on a large scale setting.
ABSTRACT from Royal Society of Chemistry journal RSC Advances in September 2012:
“Heavy metal ions and dissolved organic compounds in waste water are known to adversely affect human health, aquatic life and the overall ecosystem. Many hazardous pollutants need to be removed from drinking water; however, such technologies are not accessible for economically disadvantaged people around the world.
Naturally abundant tomato peels or other biomembranes are used as an efficient biomaterial to remove toxic metal ions and organic pollutants from aqueous solution. The functional groups and morphologies of the tomato peels were characterized using FT-IR and FESEM, respectively.
Factors such as pH, nature and amount of adsorbent used for extraction were studied to establish the optimum conditions.
The maximum adsorption capacity was observed at different pH values for different pollutants. The equilibrium adsorption data were interpreted by using Freundlich and Langmuir isotherms and the adsorption mechanism was investigated by kinetic studies.”
Recently, in another experiment by the same researchers, where the surface of apple peels was immobilized with naturally occurring zirconium oxides, phosphate, arsenate, arsenite, and chromate ions were again efficiently removed from aqueous solutions and such could also be applicable on a large scale setting.
ABSTRACT from American Chemical Society journal ACS Applied Materials & Interfaces in May 2013:
“The presence of anions such as chromate, arsenate, and arsenite in drinking water is a major health concern in many parts of the world due to their high toxicity. Removal of such anions from water using low cost biomass is an efficient and affordable treatment process. Owing to the easy availability and biodegradability, we chose to use apple peel as a substrate for our investigations.
Zirconium cations were immobilized onto the apple peel surface and used for the extraction of anions. Zirconium loaded apple peels were used to extract anions such as phosphate, arsenate, arsenite, and chromate ions from aqueous solutions. The presence of Zr cations on the apple peel surface was characterized using XPS.
The modified adsorbent was characterized using SEM, EDS, and FT-IR. Zr treated apple peels showed efficient adsorption toward AsO2– (15.64 mg/g), AsO43– (15.68 mg/g), Cr2O72– (25.28 mg/g), and PO43– (20.35 mg/g) anions. The adsorption and desorption studies revealed the adsorption mechanism involves electrostatic interactions.
Anion removal efficiency was estimated by batch adsorption studies. Adsorption kinetic parameters for all anions at different concentrations were described using pseudo-first-order and pseudo-second-order rate equations. Langumir and Freundlich isotherms were used to validate our adsorption data.
Arsenate and chromate anions were strongly adsorbed at the pH range from 2 to 6, while arsenite was extracted efficiently between pH 9 and 10.
Overall, the Zr immobilized apple peel is an efficient adsorbent for common anionic pollutants.”