Recent advances in nanotechnology for remediation of heavy metals.

Heavy metal contamination of the environment has become an alarming environmental issue that has constituted serious threats to humans and the ecosystem. These metals have been identified as a priority class of pollutants due to their persistency in the environment and their potential to bioaccumulate in biological systems. Consequently, the remediation of heavy metals from various environmental matrices becomes a critical topic from the biological and environmental perspectives. To this end, various research interests have shifted to the need to put forward economically feasible and highly efficient approaches for mitigating these contaminants in the environment. Thus, numerous conventional approaches have reportedly been employed for the remediation of heavy metals, with each of the methods having its inherent limitations. More recently, studies have revealed that nanomaterials in their various forms show unique potential for the removal of various contaminants including heavy metals in comparison to their bulk counterparts making them a topic of importance to researchers in various fields. Also, various studies have documented specifically tailored nanomaterials that have been synthesized for the removal of heavy metals from various environmental matrices. This review provides up-to-date information on the application of nanotechnology for the remediation of heavy metals. It highlights various nanomaterials that have been employed for the remediation of heavy metals, current details on their methods of synthesis, factors affecting their adsorption processes, and the environmental and health impact of nanomaterials. Finally, it provides the challenges and future trends of nanomaterials for heavy metal removal.

The removal of nickel and lead ions from aqueous solutions using green synthesized silica microparticles.

Silica microparticles were synthesized from sugarcane bagasse via a green synthetic technique. The prepared silica microparticles were used to remove lead and nickel ions from their separate solutions. Microscopic analysis shows that the synthesized silica particles are spherical with good monodispersed properties. The average particle diameter of the silica microparticles is estimated to be about 432 nm. Batch adsorption experiment was employed to examine the influence of adsorbent dosage, contact time, heavy metal ion concentration and pH on the adsorption efficiency of the synthesized silica microparticles in removing the studied lead (Pb2+) and nickel (Ni2+) ions from their respective solutions. An increase in adsorbent dosage, heavy metal ion concentration, contact time and pH led to an increase in the percentage removal of Pb2+ and Ni2+ metal ions from their individual solutions. The adsorption process of Pb2+ ion onto the synthesized silica microparticles followed the Langmuir adsorption isotherm (R2 = 0.961), while, the nickel ion (Ni2+) followed the Freundlich isotherm (R2 = 0.869). The adsorption process of the studied heavy metals (Pb2+ and Ni2+) in their separate solutions favours pseudo-second-order reaction model (R2, 0.978 and 0.999) over the pseudo-first-order reaction model.