Chromium removal from contaminated waters using nanomaterials – A review

Abstract

Current environmental policies aim to reduce the levels of toxic substances in aquatic ecosystems and to promote the water reuse after appropriate treatment of wastewater.Chromium is a hazard element present in effluents of various industries that should be reduced to achieve the objectives of those policies. Most of the results reported in the literature concern the use of nanomaterials for chromium sorption dissolved either in synthetic or mono-elemental spiked solutions. The present work reviews the results of research undertaken in the last decade on the application of various nanomaterials to decrease chromium concentrations in contaminated waters. Major factors influencing the removal efficiency were examined. Because most of the published studies are based on simple experiments with deionised water and mono contamination further studies are suggested focused on effects of natural and artificial chelators, interferences of other trace elements competing with chromium sorption, reduction the sorbent mass per water volume.

Effect of the Surface Charge on the Adsorption Capacity of Chromium(VI) of Iron Oxide Magnetic Nanoparticles Prepared by Microwave-Assisted Synthesis

“…Kinetic experimentation was performed at a pH of 2.5 and initial Cr(VI) concentration of 20 mg Cr /L by varying the adsorption time (5,15,30,45,60,90, 120 and 1440 min). After each adsorption experiment, the magnetic nanosorbent was separated by using a 60 × 30 mm magnet with a field at the surface of 320 kA/m.…”

“…Common drinking water can be considered toxic when it contains more than 0.05 mg/L of Cr(VI), because this chromium state is found to be highly soluble and toxic. The chromates HCrO 4− and Cr 2 O 7 2− have been discharged over the years by many industrial activities in the fields of petroleum refining, electroplating, metal coating and batteries, among others [1,5,6]. In a common wastewater treatment process, the removal of these kind of compounds takes place through chemical and physical treatments using conventional methods such as coagulation and flocculation, membrane separation, oxidation, adsorption and ionic exchange [7,8].…”

Recent advances in hexavalent chromium removal from aqueous solutions by adsorptive methods

“…Nanomaterials exhibiting high surface area, non-toxic, easy removal aer sorption, and pronounced selectivity of pollutant at trace concentrations are desirable. 42 Excitement over the application of mesoporous silica-based adsorbents was triggered by their excellent properties such as uniform pore structure consisting of well-dened pore size, high specic surface area, and larger pore size. [67][68][69][70] In Sharma et al, 65 it was pointed out that complicated synthesis, longer reaction time needed for synthesis, separation difficulties coupled with the high cost of reagents has limited the practical applications of silica adsorbents.…”

“…Typical examples include Fe 3 O 4 @titanium residue, carbon-coated montmorillonite nanocomposite, articles focused on the application of specic adsorbents such as silica-based materials, 37 polypyrrole-based adsorbents, 38 advanced carbon nanotubes, 39 clay minerals, 40 functionalized carbon nanotubes, graphene 41 and nanomaterials in general. 42 Despite the extensive existence of adsorbents for Cr(VI) removal from aqueous solutions, new adsorbents, and modication of existing adsorbing materials have been recently reported. 3,[43][44][45][46][47][48][49][50] Unlike in previous review articles, [37][38][39][40][41] this work focused on reviewing the major adsorbents reported in the literature (up to the year 2019) mainly for the removal of Cr(VI) from aqueous solutions.…”

Comparing the Adsorption Performance of Multiwalled Carbon Nanotubes Oxidized by Varying Degrees for Removal of Low Levels of Copper, Nickel and Chromium(VI) from Aqueous Solutions

“…Even so, many review papers have recognized gaps in the current knowledge, whereby the majority of studies conducted concern the adsorption of very high concentrations of the heavy metals investigated, or do not explore the effects of preparation conditions on the functionalized nanomaterials (such as oxidation process duration, etc.) or the combined effects of different parameters on the adsorption process, or do not investigate the potential mechanism and chemistry involved in the heavy metals removal [1,4,10,11,[13][14][15][16]. Oxidation of CNT is one of the simplest and therefore most economically viable functionalization techniques [10].…”