Preparation of Nano-Iron Loaded Cassava Fibre Composite Material for Hexavalent Chromium Removal

Waste cassava fiber and tea polyphenols were used as carrier materials and reducing agents, respectively, to prepare nano-iron loaded cassava fiber composite (CF-FeNPs). This work investigated the factors affecting the removal of Cr(Ⅵ) by CF-FeNPs under different environmental conditions and the removal mechanism. The SEM characterization results show that as the initial Fe2+ concentration increases, the amount of nano-iron on the surface of the composite material increases. The results show that the increases of the initial Fe2+ content and dosage of CF-FeNPs can enhance the removal rate. Meanwhile, the decrease of the initial concentration of Cr(Ⅵ) solution and pH also beneficial for the removal performance. When pH=2.0 and the initial concentration of Cr(Ⅵ) is 10 mg/L, the removal rate of hexavalent chromium by CF-FeNPs can reach 81.4% within 2 h. The reaction conforms to the pseudo first-order kinetic model. The results of this study can provide technical reference for the remediation and treatment of Cr(VI)-containing wastewater.

Effects of pouring technique on orientation of steel and synthetic macrofibres in fibre-reinforced concrete

Fibre-reinforced concrete is a short-fibre composite material, whose properties are significantly dependent on the orientation of the mixed fibres. As a starting point, the fibres are assumed to be uniformly distributed and have a uniform orientation. However, in reality, they have a non-uniform distribution owing to various factors. Such deviations in the orientation may have a significant effect on the material parameters, both favourable and unfavourable. In this study, the orientation factors determined based on the mixing models reported in the literature are compared with the results of experimental tests performed in the laboratory, and the effects of the formwork and the pouring methods used on the orientation of both steel and synthetic macrofibres are investigated. Based on the results of the study, the orientation of the fibres (both, steel and macro synthetic) significantly depends on the pouring method, which considerably influences the material parameters of fibre-reinforced concrete.