Concurrent adsorption and reduction of chromium(VI) to chromium(III) using nitrogen-doped porous carbon adsorbent derived from loofah sponge

• A high-efficiency N-doped porous carbon adsorbent for Cr(VI) was synthesized. • The maximum adsorption capacity of Cr(VI) reached up to 285.71 mg/g at 318K. • The potential mechanism for Cr(VI) adsorption by NHPC was put forward. • DFT analyzed the adsorption energy and interaction between NHPC and Cr(VI). To develop highly effective adsorbents for chromium removal, a nitrogen-doped biomass-derived carbon (NHPC) was synthesized via direct carbonation of loofah sponge followed by alkali activation and doping modification. NHPC possessed a hierarchical micro-/mesoporous lamellar structure with nitrogen-containing functional groups (1.33 at%), specific surface area (1792.47 m²/g), and pore volume (1.18 cm³/g). NHPC exhibited a higher Cr(VI) adsorption affinity than the HPC (without nitrogen doping) or the pristine loofah sponge carbon (LSC) did. The influence of process parameters, including pH, dosage, time, temperature, and Cr(VI) concentration, on Cr(VI) adsorption by NHPC were evaluated. The Cr(VI) adsorption kinetics matched with the pseudo-second-order model (R²≥0.9983). The Cr(VI) adsorption isotherm was fitted with the Langmuir isotherm model, which indicated the maximum Cr(VI) adsorption capacities: 227.27, 238.10, and 285.71 mg/g at 298K, 308K, and 318K, respectively. The model analysis also indicated that adsorption of Cr(VI) on NHPC was a spontaneous, endothermal, and entropy-increasing process. The Cr(VI) adsorption process potentially involved mixed reductive and adsorbed mechanism. Furthermore, computational chemistry calculations revealed that the adsorption energy between NHPC and Cr(VI) (−0.84 eV) was lower than that of HPC (−0.51 eV), suggesting that nitrogen doping could greatly enhance the interaction between NHPC and Cr(VI).     

Comparison of four supports for adsorption of reactive dyes by immobilized Aspergillus fumigatus beads

Four materials, sodium carboxymethylcellulose (Na-CMC), sodium alginate (SA), polyvinyl alcohol (PVA), and chitosan (CTS), were prepared as supports for entrapping fungus Aspergillus fumigatus. The adsorption of synthetic dyes. Reactive Brilliant Blue KN-R, and Reactive Brilliant Red K-2BP, by these immobilized gel beads and plain gel beads was evaluated. The adsorption efficiencies of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by CTS immobilized beads were 89.1% and 93.5% in 12 h, respectively. The adsorption efficiency by Na-CMC immobilized beads was slightly lower than that of mycelial pellets. But the dye culture mediums were almost completely decolorized in 48 h using the above-mentioned two immobilized beads (exceeding 95%). The adsorption efficiency by SA immobilized beads exceeded 92% in 48 h. PVA-SA immobilized beads showed the lowest adsorption efficiency, which was 79.8% for Reactive Brilliant Red K-2BP and 92.5% for Reactive Brilliant Blue KN-R in 48 h. Comparing the adsorption efficiency by plain gel beads, Na-CMC plain gel beads ranked next to CTS ones. SA and PVA-SA plain gel beads hardly had the ability of adsorbing dyes. Subsequently, the growth of mycelia in Na-CMC and SA immobilized beads were evaluated. The biomass increased continuously in 72 h. The adsorption capacity of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by Na-CMC immobilized beads was 78.0 and 86.7 mg/g, respectively. The SEM micrographs show that the surface structure of Na-CMC immobilized bead is loose and finely porous, which facilitates diffusion of the dyes.     

带坞舱船舶尾舱消浪装置消浪性能研究

目的 带坞舱船舶尾部具有与外界连通的自由液面,由于船舶运动会在坞舱内产生波浪,形成有害的波浪砰击,影响舱内装备的正常作业。针对这一问题,系统地对带坞舱船舶尾舱内的消浪方案进行模拟与优化,提出一套具有良好消浪性能的消浪装置方案。方法 以荷兰皇家海军两栖运输船为目标进行三维建模,使用CFD方法对其进行不同波浪下船舶响应模拟和分析,监测船舶的运动响应和舱内多个监测点的波高情况,使用多孔挡板为基础,给出一套消浪装置,并进行带有消浪装置方案的船舶响应模拟,评估该消浪装置方案的消浪性能。结果 对舱内首端和侧壁布置多孔板消浪装置,消浪效果可达40%~50%,验证了该消浪装置的可行性。结论 采用多孔介质区域模型对带有多孔介质消浪装置的整船进行数值模拟,在计算效率远高于对实际物理模型建模的同时,可以得到较好的消浪效果。