Amination of biochar surface from watermelon peel for toxic chromium removal enhancement

Watermelon peel residues were used to produce a new biochar by dehydration method. The new biochar has undergone two methods of chemical modification and the effect of this chemical modification on its ability to adsorb Cr(VI) ions from aqueous solution has been investigated. Three biochars, Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, were made from watermelon peel via dehydration with 50% sulfuric acid to give Melon-B followed by oxidation with ozone and amination using ammonium hydroxide to give Melon-BO-NH_2 or Triethylenetetramine(TETA) to give Melon-BO-TETA. The prepared biochars were characterized by BET, BJH,SEM, FT-IR, TGA, DSC and EDAX analyses. The highest removal percentage of Cr(VI) ions was 69% for Melon-B,98% for Melon-BO-NH_2 and 99% for Melon-BO-TETA biochars of 100 mg·L~(-1) Cr(VI) ions initial concentration and 1.0 g·L~(-1) adsorbents dose. The unmodified biochar(Melon-B) and modified biochars(Melon-BO-NH_2 and Melon-BO-TETA) had maximum adsorption capacities(Qm) of 72.46, 123.46, and 333.33 mg·g~(-1), respectively.The amination of biochar reduced the pore size of modified biochar, whereas the surface area was enhanced.The obtained data of isotherm models were tested using different error function equations. The Freundlich,Tempkin and Langmuir isotherm models were best fitted to the experimental data of Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, respectively. The adsorption rate was primarily controlled by pseudo-second–order rate model. Conclusively, the functional groups interactions are important for adsorption mechanisms and expected to control the adsorption process. The adsorption for the Melon-B, Melon-BO-NH_2 and Melon-BO-TETA could be explained for acid–base interaction and hydrogen bonding interaction.     

The structure of an electronegative magnetized plasma sheath with non-extensive electron distribution

In this paper, an electronegative magnetized plasma sheath model with non-extensive electron distribution is established, and the Bohm criterion affected by the non-extensive parameter q is theoretically derived. The ion Mach number varies with q. The numerical simulation results show that compared with electronegative magnetized plasma sheath with Maxwell distribution (q = 1), the sheath structures with super-extensive distribution (q < 1) and sub-extensive distribution (q > 1) are different. The physical quantities including the sheath potential distribution, ion density distribution, the electron density distribution, negative ion density distribution and the net space charge density distribution are discussed. It is shown that the non-extensive parameter q has a significant influence on the structure of the electronegative magnetized plasma sheath. Due to the Lorentz force, both the magnitude and the angle of the magnetic field affect the structure of the sheath, whether the electrons are Maxwell distributed or non-extensively distributed.     

Effect of the addition of rare earths on the activity of alumina supported copper cobaltite in CO oxidation,CH4 oxidationand NO decomposition

The effect of the addition of small amounts of rare earths(Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/Cu Co/Al catalyst were prepared and characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), atomic absorption spectroscopy(AAS), scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS), H2-temperature-programmed reduction(H2-TPR), electron paramagnetic resonance(EPR) spectroscopy and low temperature nitrogen adsorption. The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial reduction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/Cu Co/Al catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/Cu Co/Al and Nd/Cu Co/Al were the most active catalysts. The catalyst Ce/Cu Co/Al was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu+/Cu2+ and Ce3+/Ce4+. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.     

Critical parameters near the ferromagnetic-paramagnetic phase transition in La0.67–xYxBa0.23Ca0.1MnO3 compounds（x=0.10 and x=0.15）

The critical properties of the mixed manganite La0.67–x Y x Ba0.23Ca0.1Mn O3 with x=0.10 and x=0.15 around the paramagnetic(PM)-ferromagnetic(FM) phase transition were investigated through various techniques. These involved modified Arrott plots, Kouvel-Fisher method and Widom scaling relation. Magnetic data, analyzed in the critical region, using the above methods, yielded the critical exponents for(x=0.10) La0.57Y0.10Ba0.23Ca0.1Mn O3(β=0.312±0.002 and γ=1.147±0.003 at T C=299.23±0.05 K). Moreover, the estimated critical exponents of(x=0.15) La0.52Y0.15Ba0.23Ca0.1Mn O3 were β=0.286±0.004 and γ=0.943±0.002 at T C=289.53±0.06 K. The critical exponents’ values were close to the theoretical values of 3D-Ising model and tricritical mean-field model. These results suggested that the present composition should be close to a tricritical point in the La0.67–x Y x Ba0.23Ca0.1Mn O3 phase diagram. Expressing the field dependence as ΔS M∝H n allowed us to establish a relationship between the exponent n and the critical exponents of the material and to propose a phenomenological universal curve for the field dependence of ΔS M.     

铁素体渗氮工艺模拟

纯铁的莱勒图被广泛用于选择合金钢的渗氮工艺。本文首次采用计算热力学来确定AISI 4140钢的莱勒图。研究表明，AISI 4140钢的莱勒图与纯铁的存在明显差异。对AISI 4140钢进行了渗氮试验，目的是验证计算热力学的预测结果。扫描电镜结果显示化合物层中存在两种相，利用透射电镜对化合物层与扩散层界面的研究结果证实了γ′-Fe4N和ε-Fe2－3（C，N）相的共存。这些试验结果与用计算热力学建立的AISI 4140钢莱勒图高度吻合。     

表面粗糙和带槽的湿式离合器接合的有限元模型

已经开发了一个有限元模型,研究表面粗糙和带槽纸质可渗透的湿式离合器的接合特性。采用有限元方法(Galerkin)离散修正雷诺和力平衡方程式,采用等参量方程式解所描述的有关内何学。通过Patir和Cheng(1978)的通用流量模型模拟表面粗糙度的影响。在表面粗糙状况下,采用Greenwond和William son(1966)方法计算负荷分配,采用开发的有限元模型研究所加负荷的影响,以及湿式离合器摩擦材料的渗透率和槽出入口尺寸的接合特性(即转矩、油压、接合时间和油膜厚度)。研究结果表明,所加负荷、摩擦材料渗透率和槽宽度对接合特性的影响显著。高的配合面压力增大了峰值和减少了接合时间但显著增大了峰值转矩,宽油槽减少峰值转矩和增加了接合时间。对于本模型油槽深度对接合特性的影响不太明显。     

滴施腐植酸肥和化肥对辣椒生产率的影响

正采用随机区组设计,在不添加腐植酸(单独施肥)和添加腐植酸(联合施肥)的条件下,以NPK推荐施肥量100%、80%和60%的3个施肥水平,研究了NPK滴灌对辣椒养分分配和生产率的影响。在较深的土层中,联合施肥能降低土壤速效N和K含量,提高土壤速效P含量。单独施肥的基础上联合施肥,辣椒产量提高了17%~27%。联合施肥的肥