Adsorption equilibrium of heavy metals and dyes from wastewater with low-cost adsorbents: A review

This review surveyed recent publications on the adsorption uptakes of heavy metals and dyes from water and wastewater streams using low-cost adsorbents derived from agricultural waste, industrial wastes, inorganic particulates, or some natural products. Most adsorption works adopted either the Langmuir or Freundlich isotherms (or both) for adsorption data correlation. Despite a few exceptions, the waste-derived adsorbents have lower adsorption uptakes than the activated carbon. However, the cheapness of the former represents the major advantage for possible applications. Effects of process parameters, such as temperature and pH, on and the possible mechanisms to metals or dyes adsorption were addressed in some detail. We also highlighted the compensation effects during thermodynamic parameter evaluation, which were possibly overlooked in current literature.