Application of magnetic carbon nanocomposite from agro-waste for the removal of pollutants from water and wastewater.

Water pollution has significant impact on water usage, and various contaminants, such as organic and inorganic compounds, heavy metals, dyes, pharmaceuticals compounds, pathogens and radioactive compounds, are implicated. The quest for globalisation, structural developments and other related anthropogenic activities promote the release of contaminants that induce water pollution. Hence, treatment and remediation options that can remove pollutants from watercourses and wastewater have been developed. Applied nanotechnology using carbon nanocomposites has recently drawn attention because it has the advantages of low preparation cost, high surface area, pore volume and environmental stability. Magnetic carbon nanocomposites usually exhibit excellent performance in adsorbing contaminants from aqueous solutions, and thus expanding the use of nanotechnology in water treatment is of great importance. Therefore, this review explores the geographical outlook of water pollution, sources of water pollution and types of contaminants found in water and discusses the use of carbon nanocomposites as an emerging sustainable technology for water pollutant removal. The various properties of carbon-based composites influence the extent of pollutant adsorption during water treatment processes. Most carbon-based nanocomposites are generated from biomass produced by agro-waste materials. Magnetic activated carbon nanocomposites produced from walnut shells and rice husk waste can remove 78% of Cd(II) from contaminated aqueous systems. Magnetic nanocomposites from peanut shell, tea waste, curcumin nanoparticles, sunflower head waste, rice husk, hydrophyte biomass, palm waste and sugarcane bagasse facilitate hydrothermal carbonisation, chemical precipitation, co-precipitation, chemical activation, calcination and fast pyrolysis. These nanocomposites have benefitted wastewater treatment by increasing efficiency in removing pharmaceutical, dye and organic contaminants, such as promazine, ciprofloxacin, amoxicillin, rhodamine 6G, methyl blue, phenol and phenanthrene. Hence, this review discusses the relatively low costs, good biocompatibility, large surface-to-volume ratio, magnetic separation capability and reusability carbon materials and highlights the advantages of using magnetic carbon nanocomposites in the removal of contaminants from water or wastewater through adsorption mechanisms.

Phytoremediation of leachate contaminated soil: a biotechnical option for the bioreduction of heavy metals induced pollution in tropical landfill.

Metal remediation is important considering the environmental pressure due to soil pollution from landfill leachate. Hence, identifying potential plant-based option for remediation, especially the use of bio-/hyper-accumulators, is inevitable. Contamination of soil with heavy metals has been a decades-long concern. This study is therefore aimed to evaluating the metal-remediation potentials of four ornamental plant species-Cordyline fruticosa, Duranta variegated, Tradescantia spathacea, and Chlorophylum comosum-on leachate-contaminated soil. Details of the study involved leachate analysis, soil characterization, and metal-accumulation test on selected plants. Characterization of both landfill soil and leachate has indicated that Pb, Cu, As, Mn, Cr, Zn, Fe, and Ni were higher than the prescribed limits. The high metal reduction efficiency of C. fruticosa on all the studied metals was about 63%, 85%, 77.88%, 77.55%, and 75% for Pb, As, Mn, Zn, and Cr concentrations. The metal removal by the plants was significantly higher as compared to control soil (P < 0.05). The highest removal rate constant witnessed was for Mn (0.023 day-1) and was achieved using C. fruticosa. The results have revealed that C. fruticosa was the most promising plant for the removal of the studied metals. Therefore, it can be concluded that C. fruticosa has potentials to remediate heavy metal-contaminated soil at significant level. The findings will develop investigation into plant-tissue and compartmentalization effect on metal remediation using C. fruticosa.