In this study, the rice husk-based activated carbon was prepared via pyrolysis of rice husk and simultaneous KOH-activation and EDTA-4Na-modification and used for phenol adsorption from water. When the rice-husk was carbonized at 500 °C and activated at 750 °C with mass ratio of carbon to KOH of 1:3, an activated carbon can be prepared, with rich micro-porosity, high specific area of 2087 m 2 ·g −1 and maximum phenol adsorbance of 194.24 mg·g −1 . When the above activated carbon is prepared by simultaneous KOH-activation and EDTA-4Na-modification at 750 °C, N-containing functional groups were introduced to the activated carbon, which is beneficial to the adsorption of phenol . Under optimum conditions with mass ratio of carbon : KOH : EDTA-4Na = 1:3:1, the specific surface area of the resulting activated carbon decreases to 1368 m 2 ·g −1 , while its maximum adsorption capacity for phenol increases to 215.27 mg·g −1 . The adsorption kinetics of phenol on activated carbon agrees with the pseudo-second-order adsorption model, and the adsorption isotherm follows the Langmuir pattern.
Yangeng Li,Yan Kou,Keyan Sun,Jie Chen,Chengxin Deng,Chaohe Fang,Quan Shi
Phase change materials (PCMs) have attracted much attention in the field of solar thermal utilization recently, due to their outstanding thermal energy storage performance. However, PCMs usually release their stored latent heat spontaneously as the temperature below the phase transition temperature, rendering thermal energy storage and release uncontrollable, thus hindering their practical application in time and space. Herein, we developed erythritol/sodium carboxymethylcellulose/tetrasodium ethylenediaminetetraacetate (ERY/CMC/EDTA-4Na) composite PCMs with novel spatiotemporal thermal energy storage properties, defined as spatiotemporal PCMs (STPCMs), which exhibit the capacity of thermal energy long-term storage and controllable release. Our results show that the composite PCMs are unable to lose latent heat due to spontaneous crystallization during cooling, but can controllably release thermal energy through cold crystallization during reheating. The cold-crystallization temperature and enthalpy of composite PCMs can be adjusted by proportional addition of EDTA-4Na to the composite. When the mass fractions of CMC and EDTA-4Na are both 10%, the composite PCMs can exhibit the optical cold-crystallization temperature of 51.7 °C and enthalpy of 178.1 J/g. The supercooled composite PCMs without latent heat release can be maintained at room temperature (10–25 °C) for up to more than two months, and subsequently the stored latent heat can be controllably released by means of thermal triggering or heterogeneous nucleation. Our findings provide novel insights into the design and construction of new PCMs with spatiotemporal performance of thermal energy long-term storage and controllable release, and consequently open a new door for the development of advanced solar thermal utilization techniques on the basis of STPCMs.
Tao Wang,Qing Zhang,Zhongjing Zhao,Lu Zhang,Baoshan Xing
Currently, identification and regulation of adsorption sites of carbon-based materials remain a major challenge. In this study, given the properties of the target contaminant, bisphenol A (BPA), we report a novel method for preparing ultra edge N-doped hierarchically porous carbon-based material with rich vacancy defects (HENDC) via a direct pyrolysis of simultaneous EDTA-4Na and g-C 3 N 4 . Interestingly, g-C 3 N 4 kills three birds with one stone, including pore-forming agent, nitrogen configuration regulator, and structural defect former. As such, compared with that of MNDC, which was direct pyrolysis of EDTA-4Na (462.5 mg g −1 for BPA and 551.2 mg g −1 for bisphenol S (BPS)), the adsorption capacity of HENDC for BPA was 870.1 mg g −1 , which exceeded that for BPS (793.3 mg g −1 ). Also, HENDC shortened the adsorption process to 10 min for BPA compared with MNDC (30 min) and displayed a promising environmental application potential. Based on experiments and theoretical calculations, the high adsorption performance of HENDC for BPA originated from edge nitrogen doping, defect inducing, and hierarchically porous structures. Specifically, Lewis acid-base interactions of varying strength occurred between both pyridinic-N (stronger) and pyrrolic-N (weaker) with BPA. A strong π-π EDA interaction between pyridinic-N and BPA, which was further facilitated by vacancy defects in adjacent edge nitrogen. The hydrophobic effect promoted the interaction between pyrrolic-N and BPA. This work offers deep insights into effective and selective removal of BPA, suggesting new strategies for exploring cost-effective carbon-based adsorbents.
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