Ural Federal University: Scientists Synthesized an Adsorbent from Papaya Seeds

An international team of scientists has synthesized an adsorbent for wastewater treatment. This adsorbent is based on papaya seeds, inexpensive, with a high adsorption potential. It purifies water from a highly colored dye (Congo red), which is widely used in the textile, printing and plastic industries. A description of the method and the results of the study are published in the Journal of Molecular Liquids.

The new adsorbent is easy to use and not dangerous to health. It consists of papaya seed powder and iron oxide nanoparticles. The papaya seeds effectively remove the dye element from the wastewater, while the iron accelerates the sorbent’s separation from the treated water. As a result, the adsorbent removes more than 90% of the Congo red dye from the water.

“The sorbent can be cleaned and reused about five times. The powder can be washed of sorbed particles with an aqueous solution of table salt or, more effectively, with an aqueous solution of alkali. Washing with lye restores the sorption capacity of the material to more than 90%. Only during the last washing cycle there is a drop in the sorption capacity to 84%,” explains Grigory Zyryanov, a leading researcher of the Laboratory of Organic Synthesis of the UrFU Innovation Center of Chemical and Pharmaceutical Technology and a leading researcher of the Institute of Organic Compounds, Ural Branch of the Russian Academy of Sciences.

Chemists used various methods to study the adsorbent obtained, including scanning electron microscopy and X-ray spectroscopy. As a result of the experiments, scientists determined the optimal conditions under which the sorbent showed maximum efficiency of water purification.

“The sorbent works best at temperatures between room temperature and +60 ℃. A higher temperature will trigger the reverse desorption process, and in cold water the process will be slower. Also, a certain level of water acidity is needed to increase the intensity of electrostatic interactions between the dye molecules and the fragments contained in the papaya seeds. The contact time also plays a role: the maximum cleaning efficiency is reached when the sorbent is in water for at least two hours”, Grigory Zyryanov says.

In the next phase of work, chemists will test the sorbent’s effectiveness against other dyes.

Scientists point out: the problem of dye recycling in the textile, leather and dyeing industry is urgent. Dyes have a dangerous effect on human health and the environment. They do not degrade in water, but getting into the human body, they cause allergic reactions, sleep disorders, nervous disorders. In addition, when accumulated, they can cause respiratory and even cancerous diseases.

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