基于T-P模型的高低温环境型煤对甲烷吸附性能预测

为预测深部或浅部煤层不同温度和不同压力条件下的吸附等温线,选用型煤以高低温试验装置为依托,测试了温度为293.15,273.15,253.15 K的吸附等温线。基于T-P模型,利用等温吸附曲线对公式中的参数进行了合理的求解,探讨了一种简单的煤对瓦斯吸附等温线预测方法。研究表明:同一吸附平衡压力下,温度越低,煤的瓦斯吸附量越大;ε－ω吸附特征曲线与温度无关,呈现对数的形式;参数m和拟合度R2满足抛物线的关系,存在拟合效果最好时的参数m值。采用T-P模型预测得到的吸附等温线与实测的吸附等温线无论是趋势还是定量结果均十分吻合,其相对误差不超过5%。     

Leaching and sorption of neonicotinoid insecticides and fungicides from seed coatings

Seed coatings are a treatment used on a variety of crops to improve production and offer protection against pests and fungal outbreaks. The leaching of the active ingredients associated with the seed coatings and the sorption to soil was evaluated under laboratory conditions using commercially available corn and soybean seeds to study the fate and transport of these pesticides under controlled conditions. The active ingredients (AI) included one neonicotinoid insecticide (thiamethoxam) and five fungicides (azoxystrobin, fludioxonil, metalaxyl, sedaxane thiabendazole). An aqueous leaching experiment was conducted with treated corn and soybean seeds. Leaching potential was a function of solubility and seed type. The leaching of fludioxonil, was dependent on seed type with a shorter time to equilibrium on the corn compared to the soybean seeds. Sorption experiments with the treated seeds and a solution of the AIs were conducted using three different soil types. Sorption behavior was a function of soil organic matter as well as seed type. For most AIs, a negative relationship was observed between the aqueous concentration and the log K_oc. Sorption to all soils tested was limited for the hydrophilic pesticides thiamethoxam and metalaxyl. However, partitioning for the more hydrophobic fungicides was dependent on both seed type and soil properties. The mobility of fludioxonil in the sorption experiment varied by seed type indicating that the adjuvants associated with the seed coating could potentially play a role in the environmental fate of fludioxonil. This is the first study to assess, under laboratory conditions, the fate of pesticides associated with seed coatings using commercially available treated seeds. This information can be used to understand how alterations in agricultural practices (e.g., increasing use of seed treatments) can impact the exposure (concentration and duration) and potential effects of these chemicals to aquatic and terrestrial organisms.     

Environmental transport of endogenous dairy manure estrogens

Although estrogens originating from dairy manure applied to agricultural soils as a fertilizer can potentially contaminate surface water and groundwater, the variables that control transport are poorly understood. Our objective was to assess the potential for off-site movement of endogenous dairy cattle estrogens when manure is applied on fields at agronomically relevant fertilization rates. Estrone (E1), 17α-estradiol (α-E2), and 17β-estradiol (β-E2) were used in laboratory sorption, desorption, and transformation incubations with both manure and an agriculturally relevant soil. Sorption on manure containing 44% organic carbon exceeded sorption on soil containing 0.8% organic carbon by 20 to 150 times, following the pattern of β-E2 > α-E2 > E1. Approximately 20% of E1 and 17% of α-E2 were desorbed from manure, whereas only about 4% of β-E2 was desorbed. Thirty to seventy percent of α-E2 and β-E2 were converted to E1 in soil and manure, making it imperative that transformation reactions be considered when predicting transport and potential biological effects in the environment. Overall results indicate that high organic carbon concentrations and relatively low amounts of desorption inhibit the potential for off-site transport of endogenous dairy manure estrogens.     

沉积物与水间相互作用的研究进展

本文综述了沉积物／水之间的相互作用的研究进展,主要讨论了污染物在沉积物／水界面间的物质传输：水体中污染物在颗粒物上的吸附作用;与沉积物相关的水质、健康和管理等方面的问题     

Impacts of the physiochemical properties of chlorinated solvents on the sorption of trichloroethylene to the roots of Typha latifolia

Sorption to plant roots is the first step for organic contaminants to enter plant tissues. Mounting evidence is showing that sorption to plant roots is nonlinear and competitive. The objective of this study was to investigate the effects of physiochemical properties of homologous chlorinated ethenes and ethanes on the competitive sorption of trichloroethylene (TCE) to the roots of Typha latifolia (cattail). The results showed that chlorinated ethenes exerted significantly stronger competition on the sorption of TCE than chlorinated ethanes. Individual physiochemical properties of organic compounds could be related to the competitive capacity of chlorinated ethenes, but the roles appeared secondary, with molecular structures showing primary effects. Based on these observations, a two-step sorption mechanism was proposed, consisting of the interactions between organic compounds and functional groups on the root surface and subsequent pore filling and absorption to the hydrophobic domains in the composition of roots.     

Comparison of biosorbents with inorganic sorbents for removing copper(II) from aqueous solutions

In comparison with several other reported inorganic sorbents, Camellia tree leaf and primary sludge obtained from a settling tank as a pretreatment to the activated sludge system in a Hong Kong sewage treatment plant were evaluated for removing Cu(II) from aqueous solutions. Experimental data were modeled by the Langmuir isotherm equation to estimate the maximum sorption capacity (q_max). Results show that, at pH 5.6, biosorbents, Camellia tree leaf and primary sludge in particular, exert higher sorption capacities (q_max > 40 mg g⁻¹) than inorganic sorbents, Na-montmorillonite (q_max = 33.3 mg g⁻¹), fly ash (q_max = 18.8 mg g⁻¹), and goethite powder (10.3 mg g⁻¹). Furthermore, a pseudo second-order kinetic model was found to properly describe the experimental data for both bio- and inorganic sorbents. Sorption of Cu(II) on the Camellia tree leaf and primary sludge were much faster than that on the inorganic sorbents. In addition, desorption tests revealed that the desorption capacities of the two biomaterials are higher than the other selected materials; and much more Cu(II) can be retrieved from the Cu(II)-loaded biosorbents. Finally, increasing solution pH was found to greatly increase q_max and accelerate sorption processes.     

Removal of uranium (VI) from aqueous solution by adsorption of hematite

Hematite, a type of inorganic-sorptive medium, was used for the removal of U (VI) from aqueous solutions. Variables of the batch experiments including solution pH, contact time, initial concentration, temperature, calcium and magnesium ions were studied. The results indicated that the adsorption capacities are strongly affected by the solution pH, contact time and initial concentration. A higher pH favors higher U (VI) removal. The adsorption was also affected by temperature and calcium and magnesium ions, but the effect is very weak. The maximum adsorption capacity (q_m) only increased from 3.36 mg g⁻¹ to 3.54 mg g⁻¹ when the temperature was increased from 293 K to 318 K. A two-stage kinetic behavior was observed in the adsorption of uranium (VI): very rapid initial adsorption in a few minutes, followed by a long period of slower uptake. It was found that an increase in temperature resulted in a higher uranium (VI) loading per unit weight of the sorbent. The adsorption of uranium by hematite had good efficiency, and the equilibrium time of adsorbing uranium (VI) was about 6 h. The isothermal data were fitted with both Langmuir and Freundlich equations, but the data fitted the former better than the latter. The pseudo-first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model were used to describe the kinetic data, but the pseudo-second-order kinetic model was the best. The thermodynamic parameter ΔG⁰ were calculated, the negative ΔG⁰ values of uranium (VI) at different temperatures confirmed the adsorption processes were spontaneous.     

Surface reaction of Bacillus cereus biomass and its biosorption for lead and copper ions

In this study, the surface chemical functional groups of Bacillus cereus biomass were identified by Fourier transform infrared （FTIR） analytical technique. It had been shown that the B. cereus cells mainly contained carboxyl, hydroxyl, phosphate, amino and amide functional groups. The potentiometric titration was conducted to explain the surface acid-base properties of aqueous B. cereus biomass. The computer program FITEQL 4.0 was used to perform the model calculations. The optimization results indicated that three sitesthree pKas model, which assumed the cell surface to have three distinct types of surface organic functional groups based on the IR analysis results, simulated the experimental results very well. Moreover, batch adsorption experiments were performed to investigate biosorption behavior of Cu（Ⅱ） and Pb（Ⅱ） ions onto the biomass. Obviously, the adsorption equilibrium data for the two ions were reasonably described by typical Langmuir isotherm.     

Nitrogen interception in floodwater of rice field in Taihu region of China

A field experiment located in Taihu Lake Basin of China was conducted,by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen(N)export in a typical rice field through"zero-drainage water management"combined with sound irrigation,rainfall forecasting and field drying,N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations,and subsequently tended to retum to the background level.Before the first field drying,total particulate nitrogen(TPN)was the predominant N form in floodwater of plots with no N input,dissolved inorganic nitrogen(DIN)on plots that received urea only,and dissolved organic nitrogen(DON)on plots treated with the mixture of urea and manure.Thereafter TPN became the major form.No N export was found from the rice field,but total nitrogen(TN)of 15.8 kg/hm~2 was remained,mainly due to soil N sorption.The results recommended the zero-drainage water management for full-scale areas for minimizing N export.     

固定化海带生物吸附剂的制备及其吸附Ni~(2+)的动力学特性

以海藻酸钠、明胶和海带粉为原料制备了固定化海带生物吸附剂。固定化海带生物吸附剂对Ni2+的吸附过程可分为3个阶段:快速吸附阶段、缓慢吸附阶段和吸附平衡阶段。动力学过程可用Lagergren准二级反应动力学方程描述,限速步骤为化学吸附。随Ni2+初始质量浓度的增加,固定化海带生物吸附剂的Ni2+吸附量逐渐增大,Ni2+去除率逐渐降低。吸附过程符合Langmuir和Freundlich吸附等温方程,说明该吸附体系既有物理吸附又有化学吸附,从吸附状态看属于多层吸附,由Langmuir吸附等温方程得出固定化海带生物吸附剂对Ni2+的最大吸附量为39.43mg/g,说明固定化海带生物吸附剂对Ni2+有较好的吸附性能。