Mengjie Zhang,Xiangpu Jiao,Dezhang Ren,Chenxin Huang,Yang Li,Duofu Chen,Zhibao Huo
The rapid development of the biodiesel industry is of significant importance for achieving carbon emission reduction in the transportation sector. However, the presence of trace amounts of water in the feedstock during biodiesel synthesis may lead to severe saponification reactions, thereby reducing the yield of fatty acid methyl esters. In this study, based on our exploration of the characteristic of porous carbon to absorb moisture from the environment, we synthesized a CaO catalyst with porous carbon coating via discarded shrimp shell biomass. Because the carbonization temperature of organic matter in shrimp shells is lower than the decomposition temperature of CaCO 3 , the CO 2 generated during pyrolysis can erode the pyrolytic carbon and form porous structure. The mesoporous carbon shell facilitates the diffusion of oil and methanol molecules while adsorbing moisture in the alcohol phase. This structure effectively minimizes the interaction between CaO and water, thereby suppressing saponification reactions and ensuring the smooth progression of the desired transesterification reaction. Through a series of physicochemical characterizations, the structure and water absorption performance of the catalyst were confirmed. The as-prepared CaO@PC-900 catalyst demonstrated the ability to maintain a biodiesel yield of over 85% in a reaction system with a water content of 3%, significantly surpassing the performance of commercial CaO and previously reported Ca-based solid bases. This work provides a new approach to the design of anti-saponification transesterification catalysts, while also offering a novel pathway for the synthesis of porous carbon from discarded crustacean biomass.
Chao He,Hengliang Lin,Leilei Dai,Rongliang Qiu,Yetao Tang,Yunpu Wang,Pei-Gao Duan,Yong Sik Ok
Shrimp processing and consumption generate large amounts of waste shrimp shell (WSS) rich in chitin and protein. Herein, we successfully synthesized WSS-based hydrochar (WSH) adsorbent through deproteinization and deacetylation followed by hydrothermal carbonization (HTC) and acid washing. For comparison, another hydrochar (CCH) adsorbent was synthesized from HTC of commercial chitosan under identical conditions. Specifically, WSH contained rich nitrogen-containing functional groups with a long aliphatic chains structure. Acid etching of calcium carbonate in WSS led to a higher specific surface area of WSH (12.65 m 2 /g) which was nearly 6 times higher than that of CCH (2.13 m 2 /g). The lower deacetylation degree of WSH was responsible for higher amide I and amino groups retained therein. Under an optimal initial solution pH of 4.0, WSH could rapidly achieve a superb adsorption capacity of 755.08 mg/g for methyl orange molecule. Moreover, the adsorption process followed a pseudo-second-order kinetics model and was well described by a monolayer adsorption pattern based on the Langmuir isotherm model with correlation coefficients higher than 0.9989. Prominent adsorption performance of WSH for methyl orange was mainly attributed to electrostatic interactions, while steric hindrance effect had a detrimental impact on the adsorption capacity of CCH. Superb adsorption capacity and excellent regeneration performance suggest WSH could be a promising and affordable adsorbent candidate for anionic dye removal.
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