Treatment of high volumes of sewage reuse containing low concentrations of pollutants is becoming increasingly important as the discharge regulations become more stringent. Most of the past work has focused on the removal of higher concentrations of pollutants and on the more traditional and more expensive adsorbents/ion-exchange materials. This work has focused on the ability of low-cost adsorbents, as compared to the more traditional adsorbents, to remove from a high-volume waste stream, low concentrations of pollutants. The low –cost adsorbents investigated in this research include Eichhornia crassipes (water hyacinth); tree leaves (Eucalyptus camaldulensis and Casuarina glauca); maize cob and rice straw waste. The natural waste materials can be possible recycled by using dilute HCl and NaOH solutions, this process will be useful for the removal of residual of metals from absorbents after treatment to be used for several times. Also, investigations were carried out using a batch sorption process, the efficiency of sorption of lead, cadmium, arsenic, aluminum, chromium, mercury, nickel, cobalt, copper and zinc ions are affected by aqueous solution, pH, contact time, type of adsorbents, initial metal ion concentration all of which factors were investigated. The pollutant removal efficiencies and capacities of these materials were compared with removal efficiencies and abilities of the more traditional adsorbents: Amberlite IR-120 (plus) and CM- Cellulose.
The results experiment for lead ion has shown that the maximum removal capacity was for Amberlite IR with a capacity of approximately 99 %, followed by the CM-cellulose. While the low-cost adsorbents, water hyacinth plant and rice straw had shown the greatest removal capacities, approximately 43 – 90 %, compared to Eucalyptus camaldulensis; Casuarina glauca and Maize cob.