Low-cost and reusable carbon black based solar evaporator for effective water desalination

Abstract

Solar distillation is considered a low-cost, environmental-friendly approach for freshwater production. However, water output and photothermal efficiency of conventional solar evaporators are low. This study developed highly efficient bilayer photothermal functional films (noted as CBMCE) by depositing carbon black nanoparticles (CBNPs) dispersion on mixed cellulose ester (MCE) support via simple vacuum filtration. To further increase water production, multilayer enhanced evaporators (MEER) were fabricated by coupling optimal CBMCE with polystyrene foam and air-laid paper. The effects of operating conditions on solar evaporation were systematically investigated, including loading rate of CBNPs on MCE, solar power densities, water depths, relative humidity, and different water types (deionized water, synthetic seawater, municipal wastewater, and 13.5 wt% NaCl solution). Experimental results indicated that the average water evaporation rate (AER) increased with increasing incident solar density and decreased with increasing water depths, aqueous solution salinity, and relative humidity. For 13.5 wt% NaCl solution, MEER achieved maximum AER of 5.6 kg·m−2·h−1, enhanced evaporation rate and evaporation efficiency by ~124.0% and ~123.5%, respectively. Economic analysis showed desalination of 13.5 wt% NaCl solution using MEER had a life cycle cost of ~$1.89/m3 fresh water produced. This study demonstrates that MEER are highly efficient, low-cost, and reusable functional materials for solar desalination.