• 2018-07
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • br Materials and methods br Results and discussion br


    Materials and methods
    Results and discussion
    Conclusions The fabrication and characterization of AMCs reinforced with SiC and RHA was done in this study. Following conclusions are drawn from the above study:
    Conflict of interest
    Authors\' contributions
    Introduction Industrialisation results in the production of large quantities of heavy metals in most parts of the world. These heavy metals tend to exist in different forms with their concentrations exceeding the normal acceptable limits in the environment [1]. Most riverbeds around the world have become the alkaline phosphatase inhibitor of heavy metals accumulation from industrial pollutants. These pose serious threat to organisms and the water quality within these ecosystems [2,3]. When dredging of these riverbeds occur to reduce the accumulation of sediments [4], these dredged materials are rarely reused because of the high concentration of heavy metals [5]. Most of these contaminated soils are landfilled to reduce their risk to the environment. In China, there are reports of accumulation of high concentrations of copper (Cu) and lead (Pb) in riverbeds and in agricultural farmlands. The major sources of Cu and Pb as pollutants in the Chinese environment are predominantly from the electronics industry, the mining and smelting industry, the agricultural practices, and from atmospheric deposition [6]. The concentration of Cu and Pb exceeding 20,000 mg/kg have been reported in sediments [7,8]. The immobilisation of Cu and Pb from sediments have been widely reported in the literature [[9], [10], [11]]. These reports have also included the environmental impacts of the immobilisation of these heavy metals on the environment and on living organisms. It is therefore important that contaminated materials containing these heavy metals are carefully handled to reduce pollution. The practice of treating the contaminated dredged materials before deposition in landfills has been widely advised. The application of solidification/stabilisation (s/s) as a technique for the treatment of such contaminated dredged materials has been widely studied and reported in the literature [12,13]. This method relies on binding materials to change the physical and chemical properties of contaminated soils. The pretreatment option chosen must always take into consideration the main factors that underlie the mobility of the heavy metals [14]. When this is properly done, the potential environmental hazard associated with the disposal of these materials will be controlled. However, heavy metals are released slowly and disperse into the environment in the long-term after the application of s/s technique as treatment option [15]. When these treated material are of low permeability, diffusion controlled process become the dominant leaching mechanism in the short and long term [16]. The study by Hashem et al. [9] on heavy metal immobilisation in treated sediments has shown that the interaction of the heavy metals and the Ordinary Portland cement (OPC) affects the hydration reactions of the cement and thereby influence the overall performance of the solidification/stabilisation process. The use of cement as the main binding material has been in practice over the last 50 years [17]. It has been reported that the manufacturing of one ton of Portland cement contributes to the environment one ton of CO2 emission [18]. With the increasing contribution of the cement industry to the global carbon dioxide emission, more studies have been devoted to pozzolanic materials for more sustainable development. The recent applications of industrial and agricultural waste to partially replace cement are found to be environmentally safe, stable, durable as well as economical [19]. Previous studies have shown that when cement and pozzolanic materials are blended it generally results in improved durability, higher sulfate resistance, and obvious economic benefits [[20], [21], [22]]. Besides the reduction in the cost of s/s treatment, pozzolanic reaction continues over a long period of time leading to a long-term stabilisation effect [20].