Chemically Dual-Modified Biochar for the Effective Removal of Cr(VI) in Solution

Here, a dual-modification strategy using KMnO4 (potassium permanganate) and AlCl3·6H2O (aluminum chloride, hexahydrate) as co-modifiers to improve the Cr(VI) removal capacity of K2CO3 activated biochar is introduced. As a result, the dual-modified biochar with KMnO4 and AlCl3·6H2O has the calculated adsorption energy of −0.52 eV and −1.64 eV for HCrO4−, and −0.21 eV and −2.01 eV for Cr2O72−. The Al2O3 (aluminum oxide) and MnO (manganese oxide) embedded on the surface of dual-modified biochar bring more Cr(VI) absorption sites comparing to single-modified biochar, resulting in a maximum Cr(VI) saturated adsorption capacity of 152.86 mg g−1. The excellent removal performance is due to the synthetic effect of electrostatic attraction, reduction reaction, complexation reaction, and physical adsorption. The experimental results also indicated that the spontaneous adsorption process agreed well with the pseudo-second order and Langmuir models. This dual-modification strategy is not limited to the treatment of Cr(VI) with biochar, and may also be incorporated with the treatment of other heavy metals in aqueous environment.

A Novel and Efficient Method for the Synthesis of Methyl (R)-10-Hydroxystearate and FAMEs from Sewage Scum

In this work, the transesterification of methyl estolides (ME) extracted from the lipid component present in the sewage scum was investigated. Methyl 10-(R)-hydroxystearate (Me-10-HSA) and Fatty Acid Methyl Esters (FAMEs) were obtained in a single step. A three-level and four factorial Box–Behnken experimental design were used to study the effects of methanol amounts, catalyst, temperature, and reaction time on the transesterification reaction using aluminum chloride hexahydrate (AlCl3·6H2O) or hydrochloric acid (HCl) as catalysts. AlCl3·6H2O was found quite active as well as conventional homogeneous acid catalysts as HCl. In both cases, a complete conversion of ME into Me-10-HSA and FAMEs was observed. The products were isolated, quantified, and fully characterized. At the end of the process, Me-10-HSA (32.3%wt) was purified through a chromatographic separation and analyzed by NMR. The high enantiomeric excess (ee > 92%) of the R-enantiomer isomer opens a new scenario for the valorization of sewage scum.

From Clay Minerals to Al2O3 Nanoparticles: Synthesis and Colloidal Stabilization for Optoelectronic Applications

This research was performed to obtain high-value products from clay materials. High-grade nanometric delta-alumina (δ-Al2O3) was obtained from the modification of clay-based minerals, which could be potentially applied in the form of thin film for novel optoelectronic applications. The selective recovery process of alumina from clay materials presents an important advantage regarding the complete removal of other starting constituents such as silica, iron, titanium, alkali, and alkaline earth metals. To accomplish the selective removal of different species, an acid leaching route was used to extract the aluminum, then the iron impurities were eliminated by alkaline precipitation. The solution was acidized to precipitate the aluminum as aluminum chloride hexahydrate. Finally, the aluminum chloride hexahydrate was calcinated to obtain nano-delta-alumina with purity of over 98.5% Al2O3. The dominating crystalline phase was delta–gamma alumina (δ-phase and γ-phase), with a particle size of <140 nm. Then, these nanoparticles (NPs) were prepared as a stable colloidal dispersion to form a mesoporous layer employing the spin-coating technique. Initially, the synthesized alumina was characterized by atomic force microscopy (AFM) and TEM to determine the particle size and its morphology, whereas the colloidal dispersion was analyzed by rheological measurements. Finally, the findings of this investigation made it possible to get thin films with good porosity, which can be used in optoelectronic applications, specifically in perovskite solar cells.