Brilliant red X-3B uptake by a novel polycyclodextrin-modified magnetic cationic hydrogel: Performance, kinetics and mechanism

A novel polycyclodextrin-modified magnetic cationic hydrogel (PCD-MCH) was developed and its performance, kinetics and mechanism for the removal of reactive brilliant red X-3B (X-3B) were studied. The results showed that the zeta-potential of PCD-MCH was 32.8 to 16.7 mV at pH 3.0–10.5. The maximum X-3B adsorption capacity of PCD-MCH was 2792.3 mg/g. The adsorption kinetics could be well-described by the Weber–Morris model and the homogeneous surface diffusion model (HSDM). Diffusion stages corresponding to surface or film diffusion, intra-particle or wide mesopore diffusion, and narrow mesopore/micropore diffusion occurred at 0–120, 120–480 and 480–1200 min, respectively. The latter two diffusion stages were rate-controlling for X-3B adsorption kinetics. At the initial X-3B concentration of 600 mg/L, the diffusion coefficient (D_s) and external mass transfer coefficient in the liquid phase (k_F) were 3 × 10^?11 cm²/min and 4.68 × 10^?6 cm/min, respectively. X-3B approaching the center of PCD-MCH particles could be observed at 360 min. At the end of the third diffusion stage, the C_p at q/q_e = 0 was 45.20 mg/L, which was close to the homogeneous C_p value of 46 mg/L along the radius of PCD-MCH particles. At pH 3.0–10.0, PCD-MCH showed stable X-3B adsorption capacities. After five regeneration-reuse cycles, the residual adsorption capacity of regenerated PCD-MCH was higher than 892.7 mg/g. The corresponding adsorption mechanism was identified as involving electrostatic interactions, cyclodextrin cavities and hydrogen bonds, of which cyclodextrin cavities showed prominent capture performance towards dye molecules through the formation of inclusion complexes.     

The effect of low-molecular-weight organic-acids (LMWOAs) on treatment of chromium-contaminated soils by compost-phytoremediation: Kinetics of the chromium release and fractionation

A soil–plant biological system was developed from chromium(Cr) polluted soil treated by the compost-phytoremediation method. The transformation and migration of the Cr in this system is comprehensively studied in this research. The results illustrated that the co-composting treatment can reduce the Cr availability from 39%(F1 was about 31% of total, F2 was about 8% of total) to less than 2% by stabilizing the Cr. However, herbaceous plants can accumulate the concentrations of Cr from 113.8 to 265.2 mg/kg in the two crops,even though the concentration of soluble Cr in the substrate soil was below 0.1 mg/L.Cr can be assimilated and easily transferred in the tissues of plants because the lowmolecular-weight organic-acids(LMWOAs) derived from the plant root increase the bioavailability of Cr. The amount of extracted Cr dramatically increased when the organic acids were substituted in this order: citric acid malic acid tartaric acid oxalic acid acetic acid. On average the maximum(147.4 mg/kg) and the minimum(78.75 mg/kg) Cr were extracted by 20 mmol/L citric acid and acetic acid, respectively. The desorption of Cr in different acid solutions can be predicted by the pseudo second-order kinetics. The exchangeable Cr, carbonate-bound Cr, and residual Cr decreased, while Fe–Mn oxide bound Cr and organic bound Cr increased in the soil solid phase. According to the experimental results, the organic acids will promote the desorption and chelation processes of Cr, leading to the remobilization of Cr in the soil.     

青海油田污水回注水质治理技术研究与应用

阐述了新技术在青海油田污水处理方面的应用。首先分析了原有技术不能将水处理达标的原因,然后针对污水的特性,设计了一套新的处理工艺及相关的水处理药剂。新工艺处理后的水不仅在联合站内达标,而且在注水站及注水井口也达标。新工艺彻底解决了青海油田污水处理方面的问题。     

稀土氨氮废水处理技术研究进展

本文旨在研究到目前为止前人对稀土氨氮废水处理技术的进展情况,尽管稀土氨氮废水的处理方法颇多,然而不是处理成本太高就是对水质的要求太苛刻,用于实践不太乐观;我们采用混合处理稀土氨氮废水的方法将减少处理成本,增强处理效果,如：化学沉淀＋吹脱,吹脱＋吸附等;另外,处理稀土氨氮废水要注意回收氨氮副产品,以抵消处理成本,达到清洁生产的目的。     

国内外相关标准对我国高含硫气田钻完井的适应性研究

通过对国内外含硫气井钻完井相关标准的调研,分析了国内外相关标准对我国高含硫气田钻完井的适应性。     

动态系统物元模型在综合水质预报中的研究和应用

在研究物元分析理论的基础上,以不同时段的水体综合水质建立动态系统物元,运用综合评判模型对其进行综合水质评定,并通过建立回归预警模型进行综合水质预报。在实例应用中取得了较满意的结果,论证了该方法的合理性和可靠性,为环境质量预测提供了一种全新的思路和方法。     

Isolation and identification of a bioflocculant-producing strain and optimisation of cultural conditions via a response surface model

A bioflocculant-producing strain named MY6-2 was isolated from a mixed activated sludge by a nitrogen-free medium. Based on 16S rDNA sequence, biochemical and morphological characteristics, the strain MY6-2 was identified as Bacillus mucilaginosus. The chemical analysis indicated that the flocculant MY6-2 was mainly composed of extracellular polysaccharide. The result of the composition of the medium showed that MY6-2 was able to generate bioflocculant in a nutrient-poor medium that consisted of 5?g?L^?1 sucrose and no nitrogen source. Response surface methodology (RSM) was used to optimise the fermentation condition of MY6-2 for maximum flocculating activity by using central composite design (CCD). Based on the result, the optimum conditions were as follows: 100?mL of broth in a 250?mL Erlenmeyer flask, initial pH 8.0 and inoculum concentration 10%, respectively. The highest flocculating rate of 90% was achieved under these conditions by adding 0.5?mL fermentation supernatant to 95?mL of Kaolin suspension.     

Highly degradable chitosan-montmorillonite (MMT) nanocomposite hydrogel for controlled fertilizer release

● A controlled-release fertilizer was developed based on chitosan biopolymer scaffold. ● Chitosan-MMT scaffold achieved a well-controlled nutrient release. ● Highly water-absorbing chitosan-MMT hydrogels enhanced the soil water retention. ● Physically crosslinked chitosan-MMT hydrogels exhibited excellent degradability. Fertilizer consumption is increasing drastically along with the rapid expansion of farming in response to the ever-growing population. However, a significant portion of the nutrients in traditional fertilizers is lost during leaching and runoff causing economic loss and environmental threats. Polymer-modified controlled-release fertilizers provide an opportunity for mitigating adverse environmental effects and increasing the profitability of crop production. Here, we present a cheap and easy-to-fabricate controlled-release fertilizer excipient based on hydrogels scaffolded by safe and biodegradable chitosan and montmorillonite (MMT) nanoclays. By introducing elastic and flexible physical crosslinking induced by 2-dimensional (2D) MMT nanoflakes into the chitosan hydrogel, highly swellable and degradable chitosan-MMT nanocomposites were fabricated. The addition of MMT into the chitosan hydrogels enhanced the total release of phosphorous (P) and potassium (K), from 22.0 % to 94.9 % and 9.6% to 31.4 %, respectively, compared to the pure chitosan gel. The chitosan-MMT nanocomposite hydrogel achieved a well-controlled overall fertilizer release in soil. A total of 55.3 % of loaded fertilizer was released over 15 d with a daily release of 2.8 %. For the traditional fertilizer podwer, 89.2 % of the fertilizer was washed out during the first irrigation under the same setup. In the meantime, the nanocomposites improved the water retention of the soil, thanks to its excellent water absorbency. Moreover, the chitosan-MMT nanocomposite hydrogels exhibited high degradation of 57 % after swelling in water for 20 d. Such highly degradable fertilizer excipient poses minimal threat to the long-term fertility of the soil. The engineered Chitosan-MMT biopolymer scaffold as a controlled-release fertilizer excipient provides a promising opportunity for advancing sustainable agriculture.     

臭氧氧化降解给水系统中诺氟沙星的实验研究

采用臭氧氧化技术处理给水系统中难降解的诺氟沙星(NOR),考察了NOR臭氧氧化的影响因素,得出最佳的处理条件:初始pH为8,臭氧投加量为5 mg/L,反应90 min后去除效率达31.02%,较常规处理大大提高,同时还对反应机理进行了初步探索,研究表明,NOR经臭氧氧化后生成多种小分子物质。     

磷酸活化石墨的氧还原特性以及用于微生物燃料电池阴极

研究了磷酸活化对石墨电极上氧还原反应的影响,并考察了磷酸活化石墨材料应用于微生物燃料电池阴极的可行性。首先以循环伏安和电化学阻抗谱等电化学方法考察了经磷酸活化的石墨材料的氧还原能力,发现经质量分数为85%磷酸活化12 h后其氧还原能力最强;然后将活化石墨材料应用于微生物燃料电池的阴极,进行极化曲线和功率密度曲线的测定。结果表明,磷酸活化阴极微生物燃料电池的最大功率密度可达7.92 W/m3,为未活化石墨阴极微生物燃料电池的3.4倍;同时进行了电化学比表面积的测定及FTIR的分析测定,结果表明,磷酸活化石墨颗粒的比表面积(7.716m2/g)较未活化颗粒(10.940 m2/g)略有减小,但其表面官能团的数量和种类发生了很大变化。表面官能团的变化可能是导致石墨材料氧还原能力增强及MFCs产电性能提高的重要原因。