**Mohamed A. Tahoon 1, Saifeldin M. Siddeeg 1,2, Norah Salem Alsaiari 3, Wissem Mnif 4,5 and Faouzi Ben Rebah 1,6,\***


Received: 22 April 2020; Accepted: 23 May 2020; Published: 29 May 2020

**Abstract:** The discharge of toxic heavy metals including zinc (Zn), nickel (Ni), lead (Pb), copper (Cu), chromium (Cr), and cadmium (Cd) in water above the permissible limits causes high threat to the surrounding environment. Because of their toxicity, heavy metals greatly affect the human health and the environment. Recently, better remediation techniques were offered using the nanotechnology and nanomaterials. The attentions were directed toward cost-effective and new fabricated nanomaterials for the application in water/wastewater remediation, such as zeolite, carbonaceous, polymer based, chitosan, ferrite, magnetic, metal oxide, bimetallic, metallic, etc. This review focused on the synthesis and capacity of various nanoadsorbent materials for the elimination of different toxic ions, with discussion of the effect of their functionalization on the adsorption capacity and separation process. Additionally, the effect of various experimental physicochemical factors on heavy metals adsorption, such as ionic strength, initial ion concentration, temperature, contact time, adsorbent dose, and pH was discussed.

**Keywords:** water treatment; nanomaterials; heavy metals; functionalization
