Removal of Heavy Metals from Wastewaters: A Challenge from Current Treatment Methods to Nanotechnology Applications

Abstract

Removing heavy metals from wastewaters is a challenging process that requires constant attention and monitoring, as heavy metals are major wastewater pollutants that are not biodegradable and thus accumulate in the ecosystem. In addition, the persistent nature, toxicity and accumulation of heavy metal ions in the human body have become the driving force for searching new and more efficient water treatment technologies to reduce the concentration of heavy metal in waters. Because the conventional techniques will not be able to keep up with the growing demand for lower heavy metals levels in drinking water and wastewaters, it is becoming increasingly challenging to implement technologically advanced alternative water treatments. Nanotechnology offers a number of advantages compared to other methods. Nanomaterials are more efficient in terms of cost and volume, and many process mechanisms are better and faster at nanoscale. Although nanomaterials have already proved themselves in water technology, there are specific challenges related to their stability, toxicity and recovery, which led to innovations to counteract them. Taking into account the multidisciplinary research of water treatment for the removal of heavy metals, the present review provides an updated report on the main technologies and materials used for the removal of heavy metals with an emphasis on nanoscale materials and processes involved in the heavy metals removal and detection.

Removal of Toxic Copper Ion from Aqueous Media by Adsorption on Fly Ash-Derived Zeolites: Kinetic and Equilibrium Studies

“…Copper and its compounds are widely used in many industries, such as: metal finishing, electroplating, plastics and etching [2]. A variety of traditional techniques for water treatment have been shown to be capable of removing copper from wastewater, including chemical precipitation, membrane filtration and ion exchange [3]. Adsorption can be explained as a separation process in which the components of a fluid phase are transferred to the surface of a solid material [4,5].…”

Chemical Modification of Agro-Industrial Waste-Based Bioadsorbents for Enhanced Removal of Zn(II) Ions from Aqueous Solutions

“…There are different methods to remove heavy metals from industrial wastewaters, including chemical precipitation, electrocoagulation, reverse osmosis, ion exchange, among others [ 18 , 19 , 20 , 21 ]. Nevertheless, most of them show disadvantages due to the technological requirements for installation, operation and maintenance, generation of toxic byproducts and high cost compared with methods such as adsorption [ 8 , 22 , 23 , 24 ]. Adsorption can be considered a promising alternative thanks to its relative simplicity, low cost, and high efficiency [ 25 ].…”

Hydroxyapatite Coatings on Calcite Powder for the Removal of Heavy Metals from Contaminated Water

“…All centrifuge tubes were shaken in a rotary shaker at 50 rpm for 24 h, after which the supernatant solution was separated from the sorbent by centrifugation at 4000 rpm for 10 min, filtered (0.22 µm), acidified (1% HNO 3 ) and transferred to auto-sampler vials for analysis of the remaining Zn and Cu. The ions Ca 2+ , HPO 4 2− and pH in the supernatant were also determined in separate aliquots.…”

“…The removal of heavy metals in these systems can be achieved through several processes, with the most common ones being chemical precipitation, coagulation-flocculation, membrane filtration, ion-exchange, electrochemical processes and sorption. Chemical precipitation is the simplest and most employed approach, although it consumes large amounts of chemicals and can generate an excessive amount of sludge that requires further treatment [3,4]. Coagulation-flocculation also removes heavy metals from water with reduced time to settle suspended solids, but like chemical filtration, it produces huge amounts of sludge that need to be handled and treated [3,5].…”