Recycling by product massive number of types of plastic, they each carry a resin identification code, and must be sorted before they can be recycled. This can be costly; while metals can be sorted using electromagnets, no such 'easy sorting' capability exists for plastics. In addition to this, while labels do not need to be removed from bottles for recycling, lids are often made from a different kind of non-recyclable plastic. To help in identifying the materials in various plastic items, resin identification code numbers 1-6 have been assigned to six common kinds of recyclable plastic resins, with the number 7 indicating any
Polystyrene sulfonate as calcium (Ca) and magnesium (Mg) adhere to the sulfonate groups, displacing sodium ions. The resulting solution of sodium ions is softened. Sodium polystyrene sulfonate is used as a superplastifier in cement, as a dye improving agent for cotton, and as proton exchange membranes in fuel cell applications. In its acid form, the resin is used as a solid acid catalyst in organic synthesis. Polystyrene sulfonate Polystyrene sulfonates are polymers derived from polystyrene by the addition of sulfonate functional groups. They are widely used as ion-exchange resins to remove ions such as potassium, calcium, and sodium from solutions in technical