Industrial solid waste for heavy metals adsorption features and challenges; a review

Industrial solid waste (ISW) is the waste obtained from the industrials activities which include any solid materials that are rendered useless during a manufacturing process. The ISW considers a global environmental problem and serious solutions must be taken to face this problem and decrease its environmental load and impact. Adsorption of heavy metal from industrial effluents using ISW is considered as a promising, potential and inexpensive alternative concept for ISW management. The ISW offering potential advantages as the zero cost, availability, high efficiency, and green alternative source. Heavy metals adsorption onto ISW is a complex process that affected by several factors including initial metal ions concentration, contact time, pH of the solution, temperature and adsorbent dose. In this paper, we review the factors that affect heavy metal adsorption onto ISW, such as contact time, temperature, pH, and adsorbent dose. The chief findings of the present review are: (1) The heavy metal ions removal% is high at the initial stage of the adsorption process then it decrease still it reaches equilibrium. (2) Temperature greatly affects the heavy metal adsorption process. (3) There is a definite pH value for each metal ion, at which the extreme adsorption of those metal ions occurs. (4) Increasing adsorbent dose generally increases catalytic activity due to the increase in the total surface area and the number of active places on the surface of the adsorbent. Knowing the factors that affect heavy metal adsorption onto ISW will help in optimizing the condition for heavy metal adsorption onto ISW. (C) 2020 The Authors. Published by Elsevier B.V.