Start with a cation exchange resin and plan an experiment to find the extent to which Na+ ions (from say NaCl solution) exchange with the hydrogen ions on the resin. You could Investigate the rate of exchange of ions by leaving the exchange resin in the sodium chloride solution for different periods of time (and plot graphs). Or you could investigate the effect of using different concentrations of sodium ions on the rate of exchange or the effect using cations such as potassium, calcium, aluminium, copper (II), and iron (II). Do they exchange to the same extent and at a similar rate?
Recycling an aluminium can save 95% of the energy required to produce a new can from ore. Aluminum cans are easily recycled into new aluminum cans, but they can also be recycled into other useful aluminum products. A good EEI would be to convert aluminum cans into alum (potassium aluminum sulfate). Large amounts of alum is used by the paper industry as a filler in paper and secondly for drinking water purification. Merely converting can to alum is hardly the basis for an EEI. You'd need to apply some problem-solving and creative thinking. Perhaps you could look at ways of maximizing the yields and minimizing the input energy (heat) and chemical resources (KOH).
Electrolysis is commercially highly important in the separation of elements from naturally-occurring sources such as ores using an electrolytic cell. It involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials. It is used in the production of metals such as aluminium, lithium, sodium, potassium and magnesium, and of non-metals such as chlorine. The electrolysis of water produces hydrogen and oxygen and that could make an interesting EEI.
The authors reported that, using X-ray microanalysis, the distribution of aluminium, magnesium, calcium and potassium was found to be similar in roots to those collected from declining spruce stands in Solling, Germany.