A Sustainable Process for the Recovery of Valuable Metals from Spent Lithium Ion Batteries by Deep Eutectic Solvents Leaching

The feasibility of using low-environmental-impact leaching media to recover valuable metals from lithium ion batteries (LIBs) has been evaluated. Several deep eutectic solvents (DES) were tested as leaching agents in the presence of different type of additives (i.e., H2O2). The optimization of Co recovery was carried out by investigating various operating conditions, such as reaction time, temperature, solid (black mass) to liquid (DES) ratio, additive type, and concentration. Leaching with final selected DES choline chloride (33%), lactic acid (53%), and citric acid (13%) at 55 °C achieved an extraction yield of more than 95% for the cobalt. The leaching mechanism likely begins with the dissolution of the active material in the black mass (BM) followed by chelation of Co(II) with the DES. The results obtained confirm that those leaching media are an eco-friendly alternative to the strong inorganic acids used nowadays.

Purification of Chitin from Pupal Exuviae of the Black Soldier Fly

Purpose Chitin purification from remains (pupal exuviae after metamorphosis to adult flies) of Hermetia illucens farming was optimized performing demineralization, deproteinization and bleaching under different conditions. The optimal parameters to obtain high-purity chitin were determined. Methods Dried and ground pupal exuviae, whose composition was initially determined, were demineralized using six different acids. Proteins were removed with a NaOH treatment in which temperature, molarity and duration were varied in a randomized experiment. Bleaching was carried out testing ten different chemicals, including NaOCl, H2O2, solvent mixtures and enzymes. The efficiency of each step was determined to assess the optimal conditions for each of them. The resulting chitin was subjected to spectroscopic characterization. Results The highest demineralization efficiency (90%) was achieved using 0.5 M formic acid for 2 h at 40 °C, confirming the validity of organic acids as a more sustainable alternative to inorganic acids. The treatment with 1.25 M NaOH at 90 °C for 4 h showed the highest deproteinization efficiency, removing 96% of the proteins. Temperature and NaOH concentration were the significant parameters for deproteinization efficiency. The most efficient bleaching treatment was with 6% NaOCl at 60 °C for 1 h (67% efficiency). H2O2 could also be a valid alternative to avoid environmental risk related to chlorine-containing compounds. At the end of the purification process 17% of the original biomass was retained with a chitin content of 85%, corresponding to a chitin yield of 14% related to the initial biomass. Solid-state nuclear magnetic resonance showed that the purified chitin had a degree of acetylation of 96% and X-ray powder diffraction gave a crystallinity index of 74%. Conclusion This investigation shows an optimized method for extraction of high-purity chitin from H. illucens pupal exuviae, supporting the validity of insect-farming remains as source of this versatile biopolymer. Graphical Abstract

Prediction of phenolic compounds and glucose content from dilute inorganic acid pretreatment of lignocellulosic biomass using artificial neural network modeling

Dilute inorganic acids hydrolysis is one of the most promising pretreatment strategies with high recovery of fermentable sugars and low cost for sustainable production of biofuels and chemicals from lignocellulosic biomass. The diverse phenolics derived from lignin degradation during pretreatment are the main inhibitors for enzymatic hydrolysis and fermentation. However, the content features of derived phenolics and produced glucose under different conditions are still unclear due to the highly non-linear characteristic of biomass pretreatment. Here, an artificial neural network (ANN) model was developed for simultaneous prediction of the derived phenolic contents (CPhe) and glucose yield (CGlc) in corn stover hydrolysate before microbial fermentation by integrating dilute acid pretreatment and enzymatic hydrolysis. Six processing parameters including inorganic acid concentration (CIA), pretreatment temperature (T), residence time (t), solid-to-liquid ratio (RSL), kinds of inorganic acids (kIA), and enzyme loading dosage (E) were used as input variables. The CPhe and CGlc were set as the two output variables. An optimized topology structure of 6–12-2 in the ANN model was determined by comparing root means square errors, which has a better prediction efficiency for CPhe (R2 = 0.904) and CGlc (R2 = 0.906). Additionally, the relative importance of six input variables on CPhe and CGlc was firstly calculated by the Garson equation with net weight matrixes. The results indicated that CIA had strong effects (22%-23%) on CPhe or CGlc, then followed by E and T. In conclusion, the findings provide new insights into the sustainable development and inverse optimization of biorefinery process from ANN modeling perspectives. Graphical Abstract

Poly Methyl Methacrylate (Pmma) Based Polyaniline Composite for Ammonia (Nh3) Gas Sensors

Inorganic acids (HCl, H2SO4, and H3PO4) doped-PMMA/PANI composites are prepared by in-situ technique via oxidation-polymerization process. Different techniques such as XRD, FTIR, UV-Visible, four-probe method are used to characterize the composite. Presence of different chemical group of the doped composites is analysed by ATR-FTIR spectroscopic analysis. Charge carrier behaviour of the doped composite is analyzed by UV-Visible spectroscopy. Band gap (Eg) of the doped composites is determined from UV-Visible absorption analysis using Tauc expression. The estimated direct band gap energy (Eg) is found to be 1.93 eV (for HCl doped PMMA/PANI composite), 1.19 eV (for H2SO4 doped PMMA/PANI composite), and 1.71 eV (for H3PO4 doped PMMA/PANI composite), respectively. DC-conductivity is measured with and without magnetic field. Temperature dependent DC conductivity is also measured. In addition, we were discussed the response of ammonia (NH3) gas with polyaniline-based sensor materials.

Solubility of metals content bangka tin tailings sand using inorganic acids

Research entitled Solubility of Metals Content Bangka Tin Tailings Sand Using Inorganic Acids The sample used was tailings sand from tin mining on Bangka Island which was destroyed using several variations of inorganic acids alone, H2SO4, HNO3 and HCl and mixed with H2SO4-HCl, H2SO4-HNO3, HNO3-HCl and H2SO4-HNO3-HCl. Metal content characterization was analyzed using XRF. From the results of the analysis, it was found that the average heavy metals and rare earth metals were more in HNO3 while for a mixture of acids, namely the use of H2SO4-HNO3.

Extension of the method for identifying crystals in the composition of wine sediment

Одной из функций технохимического контроля в виноделии является обеспечение разливостойкости готовой продукции. Для этого необходима система методов и тестов, позволяющих оценить склонность вин к помутнениям физико-химического характера, также установить причины появления осадков, образующихся в случае недостаточной технологической обработки вин или при нарушениях условий их хранения. В случае кристаллического осадка общепринятым методом идентификации калиевой или кальциевой природы виннокислой соли является воздействие 10 %-ными растворами соляной и серной кислот. Указанные кислоты в более высокой концентрации являются прекурсорами, применение которых строго регламентируется на законодательном уровне. Целью данной работы являлось обоснование возможности применения общедоступных реактивов при анализе кристаллического осадка вин. Объектами исследований являлись растворы неорганических кислот и сульфата натрия в качестве источника сульфат-аниона, кристаллический осадок вин, а также промышленные препараты битартрата калия и тартрата кальция. Показано, что эффективной заменой соляной и серной кислот для растворения кристаллов является азотная кислота. Предложен новый реагент для идентификации калиевой и кальциевой природы осадка, представляющий водный раствор азотной кислоты (10 %) и сульфата натрия (не менее 15 %). Растворение виннокислых кристаллов в капле данного препарата свидетельствует, что кристаллообразующим катионом является калий; появление отдельных звездчатых, игольчатых структур или их сростков демонстрирует присутствие кальция. Усовершенствованная методика предназначена для применения в рамках технохимического контроля в лабораториях винодельческих предприятий, профильных учебных и научных заведений. One of functions of techno-chemical control in winemaking is to ensure wine stability of the finished product after bottling. This requires a system of methods and tests to assess the tendency of wines to haziness of physicochemical nature, as well as to establish the appearance origin of sediment formed as a result of insufficient technological processing of wines or violation of the storage conditions. In the context of crystal sediment, the action of 10% solutions of hydro-chloric and sulfuric acids is a generally accepted method for identifying the potassium or calcium nature of tartrate salts. In a higher concentration, these acids are precursors, using of which is strictly regulated at the legislative level. The purpose of this work was to substantiate the possibility of using generally available reagents in the analysis of crystal sediment of wines. The objects of research were solutions of inorganic acids and sodium sulfate as a source of sulfate-anion, crystal sediment of wines, as well as commercial preparations of potassium bitartrate and calcium tartrate. It is indicated that nitric acid is an effective substitution for hydrochloric and sulfuric acids to dissolve crystals. New reagent, constituting aqueous solution of nitric acid (10%) and sodium sulfate (not less than 15%), is proposed for identifying the potassium or calcium nature of the sediment. Dissolving of tartaric crystals in a drop of this preparation indicates that potassium is a crystal-forming cathion; the appearance of single stellar, needle-like structures or their intergrowth demonstrates presence of calcium. The extended technique is intended for application as a part of techno-chemical control in laboratories of winemaking enterprises, industry-specific educational and scientific institutions.