Yingjun Qiao,Xianyang Dai,Bing Zhao,Zhiqiang Qian,Zhijian Wu,Zhong Liu
It is highly appealing to use titanium-based adsorbents (like H 2 TiO 3 (HTO)) that have a high capacity and selectivity to directly extract Li + from an aqueous solution. However, HTO still faces the problems of low actual adsorption capacity and dissolution of Ti 4+ , and the application of powder adsorbents is limited by poor fluidity and poor recyclability. In this work, a multi-scale modification strategy was adopted. At the atomic-scale, we prepared Ni-doped HTO-Ni-2 % powder which exhibited higher adsorption capacity (33.27 mg/g) and lower dissolution rate of Ti 4+ (2.2 %) compared to undoped HTO (29.73 mg/g and 2.63 %). Computational studies showed that Ni doping replaced Li in the (Li) layer, resulting in more stable Ni O bonds and enhanced electronic transition ability. At the micro-scale, we have achieved successful granulation of HTO-Ni-2 % using ethylene vinyl alcohol (EVOH) as a binder for the first time. Owing to the increased hydrophilicity by EVOH, the spherical adsorbents exhibited impressive performance, achieving adsorption equilibrium in a short time while maintaining a considerable adsorption capacity (24 h, 10.2 mg/g), and having lower Ti 4+ dissolution. These results have significant implications for developing efficient adsorbents for lithium extraction.
The closed pores and slow kinetics of conventional Ti-based adsorbents (HTO) hinder their industrial application in the selective adsorption of Li + from wastewater. Herein, a surface modification and spatial optimization strategy was developed to improve the adsorption performance of HTO for Li + . The strong hydrophilicity caused by high roughness of modified HTO increases the contact area between the Li + -containing solution and the absorbent, which shortens the diffusion path of Li + to the adsorbent surface and accelerates the migration of Li + to the adsorbent surface. The excellent lithium affinity of N heteroatom on the surface of modified HTO promotes the conversion of hydrated Li + into activated Li + , which can be easily captured by the adsorbent. The large specific surface area of modified HTO provides abundant absorption sites of Li + . The material with rich pores provides sufficient space to improve the adsorption capacity of Li + . The small particle size shortens the transport path of Li + from the adsorbent surface to its interior, thereby reducing the transport resistance, which accelerates the migration of Li + into the adsorbent and releases a large number of active sites on the surface. The experimental results show that the Li + adsorption rate is increased from 0.37 mg·g −1 ·min −1 to 0.82 mg·g −1 ·min −1 after modification. The adsorption capacity of the adsorbent is 49.05 mg·g −1 and it remains 96.7 % after 5 cycles, indicating excellent adsorption performance and recyclability. This study provides a strategy for effective extraction of Li + from low concentration solutions.
Ultra-deep desulfurization of transformer oil is of great demand among power industry. In this work, the effective and deep removal of various types of organosulfurs, including mercaptan, sulfide and disulfide via catalytic adsorptive desulfurization (CADS) using bifunctional Ti-based adsorbent is reported. Compared to adsorptive desulfurization (ADS), dramatically improvement of the organosulfur uptakes were achieved under CADS process. The equilibrium adsorption capacity at 5 μg∙g −1 S reached up to 15.7, 33.4, 11.6 and 11.9 mg∙g −1 for propyl mercaptan( n -PM), dimethyl sulfide(DMS), di- t -butyl disulfide (DTBDS) and dibenzyl disulfide (DBDS), which was 262, 477, 97 and 128 times to that of ADS process, respectively, and was the highest among the reported desulfurization adsorbents. Moreover, it achieved superior breakthrough capacity of 2050, 530 and 210 ml F·(g A) −1 at the breakthrough S concentration of 1 μg∙g −1 of the commercial transformer oil S containing 10, 50 and 150 μg∙g −1 , respectively. The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant, which can be readily captured by silanol groups on SiO 2 through H-bonding interaction. The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment. This work provides an effective and economic approach for the elimination of trace amount of mercaptan, sulfide and disulfide from transformer oil.
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