Rice husk as a low-value agricultural by-product can be made into sorbent materials which are used in heavy metal and dye removal. It has been investigated as a replacement for currently expensive methods of heavy metal removal from solutions. Currently, the study of rice husk as a low-cost sorbent for removing heavy metals has regained attention. The heavy metals being studied are: As(V) [1], Au [2,3], Cr(IV) [4], Cu and Pb [5,6], Fe, Mn, Zn, Cu [7] and Cd(II) [8-10]. Rice husk is also being used to treat textile dyes such as like malachite green [11,12] and acid yellow 36 [13]. The treatment and preparation of rice husk activated carbon are of importance and became a subject of study [14-16]. In this review an extensive list of previous and current literature on rice husk activated carbons in removing heavy metals and dyes, their preparation or treatment and isotherms studies were complied to provide a summary of available information on rice husk and its potential as a low-cost sorbent.

Adsorbents prepared from palm kernel shell, an agricultural waste product, were used to remove a dye, Basic Blue 9, from an aqueous solution in batch mode at a constant temperature of 28°C. The sorption kinetics and equilibrium of basic dye onto palm kernel shell activated carbon (PKSAC) were studied. The isotherm data were well described by the Redlich-Peterson isotherm model, with constants obtained from non-linear regression. The sorption kinetics are well described by the pseudo-second-order kinetic model. These studies suggested that PKSAC could be used as low-cost alternatives in wastewater treatment for dye removal.