H2O2 treatment with rGO surface coating for interfacial solar evaporation of river sediment drying

Interfacial solar evaporation is a low-energy, low-carbon emission method used to enhance seawater desalination and sewage treatment. In this work, this technology is employed for drying of river sediment. This is an innovative approach to solve the perpetual problem of large volume and high water content river sediment. Reduced graphene oxide (rGO) is coated on to the surface of the mud to enhance photothermal conversion, and H2O2 is used to condition the properties of the sediment so that multitudinous pores are formed inside the mud cake aiding heat convection transfer. These two strategies were implemented simultaneously to promote drying efficiency. Indoor simulated evaporation for 2 h under 1.0 sun illumination of sediment (3 cm thickness) conditioned using 62.5 mL·kgDS-1 H2O2 (H2O2 solution concentration of v/v 30%, DS – dry solids) coated with 97 g m−2 rGO, compared with the original mud without any treatment, resulted in an increase in evaporation rate of 40%. In outdoor experiments (5 h) the evaporation rate was increased by 54%, confirming that H2O2 coupled with rGO can effectively enhance the drying efficiency of interfacial solar evaporation for river sediment. Evaporation tests on different thicknesses of sediment showed that the thinner the mud cake the more favorable it is for drying. The water diffusion coefficient in the mud cake treated with 62.5 mL·kgDS-1 of H2O2 (30% v/v) and 97 g m−2 rGO was 9.73 × 10−8 m2 s−1. The untreated mud cake that had water diffusion coefficient of 3.86 × 10−9 m2 s−1. The logarithmic thin layer model was found to describe the sediment drying process well.