This paper examined the competitive removal of metal ions from quaternary aqueous solutions containing Ni²⁺, Mn²⁺, Cr⁶⁺, and Cd²⁺ using adsorption on both acid-modified and unmodified activated carbon. Activated carbon (AC) was oxidized with nitric acid, both in granular (AGC) and powder (APC) forms, and tested for the competitive adsorption of Ni²⁺, Mn²⁺, Cr^6+, and Cd²⁺ from an aqueous solution. Surface oxidation led to a reduction in BET surface area and HK pore width and an increase in the intensities of hydroxyl and carboxyl functional groups for both AGC and APC compared to unmodified activated carbon, AC, as indicated with BET and FTIR analyses. The adsorption capacity of all four metal ions on AC was in the order Ni²⁺ > Cd²⁺ > Cr⁶⁺ > Mn²⁺, while it was altered for the two oxidized AGC and APC carbons to be Cr⁶⁺ > Ni²⁺ > Cd²⁺ > Mn²⁺. Acid treatment resulted in high selectivity for Cr⁶⁺ over all other available ions with a 100% removal efficiency, while it decreased for Ni²⁺, Cd^2+, and Mn²⁺ compared to AC. This improvement in Cr⁶⁺ adsorption is due to its higher ionic potential and smaller size, which results in a faster diffusion and stronger adsorption to the acidic groups located at the pore edges. Therefore, it will repel and hinder other ions from accessing the activated carbon pores. Modeling of the adsorption isotherms with DKR was better than both Freundlich and Langmuir for the competitive ions. DKR showed strong attraction for both Ni²⁺ and Cd²⁺ by ion exchange on the AC surface, as indicated by their apparent adsorption energy (E) values. Cr⁶⁺ adsorption was found to be by physical adsorption on AC and by ion exchange on both AGC and APC. Mn²⁺ ions had a very weak attraction to all types of tested activated carbons in the presence of other ions.

Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed.

A first-time, end group thermolysis departing a urethane into propylene carbonate. This exposure produced a new amine tethering point producing a diamine-terminated oligourea ([10]-OU) as a green sorbent for CO ₂ capturing is reported.