Wood,
a natural renewable material, has drawn great attention in
solar steam generation in recent years due to its intrinsic properties
such as high hydrophilicity and low thermal conductivity. Until now,
great achievements have been made in increasing the light absorption
of wood-based solar evaporators, mainly through surface carbonization
and coating. However, the complicated and cost-intensive preparation
process of the light absorption layer prevents its large-scale application.
In particular, the carbonized and coated surface could be importantly
influenced by the scouring effect of waves and the corrosion of salt
water. Herein, a facile, low-cost, and scalable in situ reduction
method has been developed to prepared KMnO4 oxidized wood
(K-wood) for solar steam generation, which not only shows high evaporation
performance but also has high structural stability. In the preparation
process, the reaction-product black MnO2 particles will
be uniformly distributed on the surface of wood, making the K-wood
exhibit a high solar absorbance of about 94%. Moreover, the K-wood
could still maintain the inherent high hydrophilicity and excellent
thermal insulation performance. Benefitting from all of these advantages,
the K-wood achieved a high evaporation rate (1.22 kg m–2 h–1) and a high evaporation efficiency (81.4%)
under 1 sun illumination (1 kW m–2). Importantly,
the K-wood also exhibits excellent structural stability, such as having
good acid–base resistance and also washing resistance, and
could even withstand an ultrasound treatment for even 2 h. The reusability
of the K-wood was also tested, and the evaporation rate remains nearly
unchanged after 20 cycles in seawater evaporation. Moreover, the condensate
water obtained by the homemade collection device shows low ion concentrations,
demonstrating that the K-wood possesses an excellent ability in seawater
desalination treatment. This study provides a simple method to manufacture
a high-strength wood-based solar steam evaporation device, which has
potential for future large-scale applications.
Four diverse microstructured MgO-stabilized CaO sorbents with varying mixing characteristics of Ca and Mg were obtained from untreated, hydrated, precipitated, and milled dolomite. Different morphological characterizations (thermal decomposition, phase composition, morphology, and nitrogen adsorption) were performed, followed by an analysis of 30 carbonation/calcination cycles in a fixed-bed reactor. The mixed metal oxide (CaO−MgO) in the fresh calcined dolomite transformed into separate crystals of CaO and MgO in the cycled sorbent and resulted in a relative decrease in the cyclic CO 2 capture capacity. Favorable structures (decreased crystallinity, increased porosity, and surface area) were generated by water hydration treatment, which was expected to enhance the recyclability, as suggested by some authors. However, this sorbent produced separate Mg and Ca as the major components, leading to a decrease in the CO 2 capture compared to fresh calcined dolomite. Complete segregation between Ca and Mg was observed upon precipitation treatment, which gave rise to the lowest cyclic CO 2 uptake. This segregation was eliminated by the final ball-milling treatment, thereby regaining the original reactivity. These results demonstrate the dominant role of the mixing of Ca and Mg on the cyclic CO 2 capture capacity of dolomite-based sorbents.
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