Turning Trash into Treasure: Pencil Waste–Derived Materials for Solar‐Powered Water Evaporation

Abstract

Solar steam generation is regarded as one of the most attractive technologies to relieve the stress of freshwater storage. Low cost and scalable production of solar evaporators is a critical issue to be considered for practical applications. Herein, the recycling utilization of pencil wastes is proposed by a facile method. A self‐floating solar evaporator made of carbonized pencil wastes can achieve an evaporation rate of 1.2 kg m−2 h−1 and a light‐to‐vapor energy conversion efficiency of 82.2% under 1.0 sun. Meanwhile, the evaporator exhibits a self‐desalting property overnight due to its superior hydrophilicity. Furthermore, the evaporator manifests significantly effective solar evaporation performance in brine, organic dye solutions, as well as other harsh conditions. Considering the wide range of raw sources, low cost, scalable preparation, and effective solar evaporation performance, the all wood waste–based solar steam generator provides an inspiration for the recycling utilization of wood wastes and the promising development of environmentally friendly biomass‐based solar evaporators.

Waste Egg Tray and Toner-Derived Highly Efficient 3D Solar Evaporator for Freshwater Generation

“…Carbonizing Platanus fruits requires a two-step heating (180 °C for 1 h and 600 °C for 1 h) for processing a three-dimensional (3D) spherical structure for solar evaporation of water, showing an evaporation efficiency of 81.3%. 33 Similarly carbonized waste products like pencil shavings (900 °C for 5 h) 34 and coffee grounds (1000 °C) 4 require high energy for processing and show efficiencies of 82.2 and 71.7% respectively, under 1 sun illumination.…”

“…Carbonizing natural biomass (i.e., loofah, bamboo, mushrooms, lotus seedpods, and so forth) − as well as waste (i.e. coffee grounds, pencil shavings, moldy bread) ,, is another way of making solar absorbers for solar thermal evaporation of water. However, carbonizing these biomass or wastes requires a very high temperature, which is energy consuming.…”

Recent Progress on the Solar‐Driven Interfacial Evaporation Based on Natural Products and Synthetic Polymers

“…Du et al [ 139 ] prepared resorcinol–formaldehyde (RF) aerogel by sol–gel polymerization, and carbonized it to obtain carbon black aerogel (CA), which was used as an SSGD under 1 sun irradiation with evaporation rate of 1.29 kg m −2 h −1 , and the water evaporation rate can be increased to 1.37 kg m −2 h −1 after CO 2 activation; the corresponding evaporation efficiency was 87.5%. The crosslinked aromatic polymer porous foam (PDVB–PS) was prepared by one‐step hydrothermal method using styrene as monomer and two vinyl benzene as crosslinking agent by Li.…”

Citric Acid-Assisted Preparation of Biochar Loaded with Copper/Nickel Bimetallic Nanoparticles

“…One way to valorize agro-wastes is via pyrolysis into biochar [1], under inert atmosphere or in the presence of very low amount of air [2][3][4]. "Biochar" is nowadays a very hot research topic because it arises from the Trash-to-Treasure concept [5,6], and thus falls within the general domain of sustainable development [7]. Much has been said on the preparation of biochar [8], and control of its composition [9], graphitization degree [10] and porosity [11] among other features [2,12,13].…”