Adsorption Of Phosphate From Aqueous Solution Using Modified Red Earth

With the development of industry and agriculture and the improvement of people's life, the excessive discharge of sewage containing phosphate causes eutrophication. Thus, it's necessary to pursue a simple, efficient and economic method for phosphorus removal.Adsorption method for phosphate removal has drawn considerable interest in recent years. Many natural and artificial materials are used as adsorbents. In order to reduce the cost and improve the efficiency, pursuing an economic and efficient adsorbent has been a hot area in the field of phosphorus removal.In this dissertation, red earth was modified with FeCl3 and the resulted modified red earth were used as adsorbent to remove phosphate. The experimental results showed that the modified red earth exhibited great efficiency and the maximum adsorption capacity was 428.4 mg/g at 35℃, The adsorption process was spontaneous and exothermic, fit Freundlich isotherm model and followed a pseudo-second-order kinetic model. The adsorption was strongly dependent on pH and temperature. As pH and the temperature increased, the adsorption capacities of the modified red earth reduced. But ion strength and coexisting ions had no obvious effect on the adsorption. The desorption studies revealed that modified red earth could be best eluted by 1 M NaOH solution and the desorption efficiency reached 98%. The adsorbent still showed a great efficiency after 4 cycles. The adsorption mechanism was mainly attributed to electrostatic interactions and surface complexations.