Clarification of nonlinear retardation factors for colloid-enhanced transport in porous media

There have been a couple of contaminant retardation factors reported for the three-phase (aqueous, solid, and colloid) groundwater system. However, the retardation factor has often been presented by itself and not incorporated into the relevant transport equation, particularly when derived from the mass fraction approach. This may cause a misunderstanding of the retardation factor especially for the systems where multi-phases exist due to the presence of colloids and/or nonlinear sorption processes are involved. It is, therefore, necessary to clarify the form of the nonlinear retardation factor along with the relevant transport equation in the multi-phase system. Alternative forms of the retardation factor and relevant transport equation for specific conditions are presented in various combinations of the nonlinearity of involved sorption mechanisms. The retardation factors for specific conditions are compared with the ones available in the literature. The results indicate that more caution should be given in applying the retardation factor in order to explore contaminant transport in the multi-phase system where any nonlinear sorption is involved. Finally, presentation of the retardation factor along with the relevant transport equation in this study would help prevent possible misuse of the retardation factor in investigating contaminant transport in the multi-phase system.     

钛酸脂改性坡缕缟石化学气相沉积生长碳纳米管

以钛酸脂改性坡缕缟石为催化剂，利用化学气相沉积法催化裂解乙炔，在高温下成功地制备了多壁碳纳米管，认为坡缕缟石释放的金属铁起到了催化乙炔的作用，讨论了它的形成条件，指出在800℃条件下生长的碳纳米管质量最好、产率最高，若催化反应温度过高则会降低产品的质量，催化温度低于700℃时不能用来制备碳管。与传统的过渡金属催化剂相比，这种矿物催化剂原料成本低廉，制备工艺简单，有利于碳纳米材料合成的工业化生产。     

压力对未熟烃源岩低温催化脂肪酸酯水解的影响

选择十八烷酸甲酯为模型化合物,以 7种抽提有机质的未熟烃源岩为载体考察了压力对未熟烃源岩矿物催化脂肪酸酯水解反应的影响。结果表明,在未熟烃源岩低温催化脂肪酸酯的水解反应中,压力是重要的影响因素,压力效应不可忽视。7种未熟烃源岩产生了不同的压力效应,并因此引起了水解率的升高或降低。文中对压力效应产生的原因进行了探讨,认为观测到的压力效应是压力对反应促进和抑制作用共同作用的结果。