4.2 Home water filters

Many people use home water filters. These effectively remove both hardness and impurities that may alter the taste of tap water, such as residual chlorine. Have you ever wondered what is inside a refill cartridge (Figure 23)?

Figure 23 Photo of a home water-filter cartridge.

Show description|Hide description

Figure 23 A photograph of a white plastic cylindrical water filter cartridge with a vertical slot which extends from the bottom about half way up the front of the cylinder. At the top of the cylinder there is a series of vertical ridges around the circumference of the cylinder.

Figure 23 Photo of a home water-filter cartridge.

• The filter contains an adsorbent material that adsorbs a wide range of compounds, including organic molecules such as pesticides.
• Activated carbon is commonly used as it has a high surface area.
• The structure of activated carbon is similar to graphite. It differs in having a smaller particle size and lower crystallinity.
• Also the edge of the graphite-like sheets (Figure 24) have been oxidised which helps improve its absorbent properties.

Figure 24 An illustration of the edge of a graphite type sheet in activated carbon.

Show description|Hide description

Figure 24 A hexagonal grid extends from the left-hand side of the figure. On the left, most of the edges of the hexagons are single lines, but moving to the right, most of the hexagons have double lines on two or three of their edges. At the top right edge, two adjacent corners of one hexagon have lines going to 'O H'. Further down one corner of a hexagon has a line to a 'C O subscript 2 H'. Near the lower right, one corner of a hexagon has a double line to an 'O'.

Figure 24 An illustration of the edge of a graphite type sheet in activated carbon.

Activated carbon is also widely used as an adsorbent to treat industrial wastewater.