Ion Exchange: The Most Important Chemical Reaction on Earth after Photosynthesis

摘要

Ion exchange is the interchange of equivalent amount of ions from the solution with ions which are swarming in a boundary of charged surface in equilibrium. It is developed due to the presence of charge in the soil colloids or layer lattice clay minerals. The source of charge developed in the colloidal surface site of soil is mainly from two processes viz. isomorphous substitution and pH dependent charge. The charge can be positive or negative due to the exchange reaction in the layer lattice. The ion exchange capacity is the sum of cation exchange capacity (CEC) and anion exchange capacity (AEC). It depends on the types of soil and the amount of charge present in the layer lattice colloidal structure. With high negative charge in the lattice surface the CEC increases and with positive charge the AEC. Ions with higher charge have larger affinity to adsorbed more strongly than lower. Ion exchange capacity in soil has the ability to retained more nutrients in the form of cations or anions making available to plant for a long time which improved the fertility of soil. Leaching loss of different nutrients from the soil is reduced by holding different ions. Ion exchange processes have been widely used for heavy metal removal for waste water treatment and water purification because of its high remedial capacity, high removal efficiency and fast kinetic. Due to its applications in agriculture, environmental management, industries, waste water treatment in mining industries,? laboratory, nanotechnology, geotechnical and other soil reclamation processes it is considered as the second most important reaction in the globe after photosynthesis.