Mechanically activated zero-valent silicon by coating silica to decolorize Acid Red 73 dye

Abstract

For the treatment of various contaminants involving the reduction action, utilization of zero-valent silicon (ZVS) may be expected due to its higher reactivity than zero-valent iron (ZVI) which has been predominantly investigated. However, the higher reactivity also means the easier passivation of ZVS, to which new approaches are required to prepare an active ZVS sample. In this study, a novel composite material consisting of microscale ZVS and silica was prepared by one-step mechanical ball milling. Such an easy operation of co-grinding allowed the generation of active ZVS sample through coating silica layer on the newly-generated surface of ZVS particles, which could prevent the easy passivation to lose reactivity when exposed to air. Typical experimental conditions for preparing active ZVS were: the mass ratio of ZVS to silica of 50 wt%, milling parameters with speed at 600 rpm and time for 60 min. A nearly complete decolorization of AR73 at a concentration of 100 mg/L was achieved by using the sample dosage at 2 g/L and stirring for 120 min. Results from this study suggest that tremendous amounts of Si sample from the solar cell after the termination of service life could serve as raw sample for preparing active reductive agents to deal with various contaminants, offering alternative to ZVI with high potentials for environmental remediation.