Activity 10: Flocculation - clay


We can separate all the project between two parts, the first one where we obtain the starch and the second one where we'll decant the clay using the starch.

The last weeks we were doing some projects studying the water sewage treatment, this one is inside the secondary treatment. Today we’re doing the flocculation that is the decantation of the clay using the starch. In this first part the aim of the study is to extract the starch of the potatoes to improve the flocculation.

To do this process we’ve used one and half more potatoes, a knife to peel the potatoes, a grater, a container to put the potatoes, a burner to burn the water  a beaker to put the water, a tripod to hold the beaker, a grid to make the tripod more stable, a strainer, a watch glass and a spatule to catch the starch.

We’ve followed some steps to do this first part; at first we have to peel the potatoes (one and half) and then scratch the with the grater, we put the potatoes in a taper with water that we had burned, we mix and compact all the solution to extract the starch. This process is possible because of the osmotic pressure, we strain the solution to separate the liquid part with the solid part. We do it three times to extract the bigger quantity of starch that it's possible from the potato, we let the dissolution repose a few hours and then we observe tang the starch precipitate cause it's not soluble in water. We catch the starch and we put it in the watch glass.

We obtain that following this steps we can separate the starch of the potato, and that because of the insolubility of the starch in water we can separate it letting the starch precipitate to repose the solution.

The second part is relationed as the same way that the first one, the difference with the fist part of the project is the aim of the study cause in this part we do the flocculation of the clay with the starch that we've obtained before. We want to see if the starch help the clay to precipitate.

We'll use three beakers, water, three pieces of clay (the blue plastic one), a spatula, an electronic scales to measure the weight of three pieces of clay, two of 1.8 grams and one of 1.3 grams, the starch, a watch glass and lemon.

Firstly we putted 160 mL of water in each beaker, then we had to chose the better clay, we tried to dissolve the clay in water when the weight of two of them is 6.4 grams and one of them is 4.3 grams; we saw that it's impossible dissolve them and we reappear all the stamps but this time putting two of 1.8 grams and one of 1.3 grams, we mixed all and cut the pieces to improve their solubility and when there's no clay at the end of the beaker. We putted two with the same weight cause one will be the control, in the two others we put starch and we wait an hour to see the differences. To see the changes we putted five drops of lemon juice in those that we've putted starch and we saw how the starch has helped the clay to precipitate.











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