Efficient HCl leaching of platinum group metals from waste three-way catalysts: A study on kinetics and mechanisms.

Waste three-way catalysts (TWCs) have attracted much attention due to the presence of platinum group metals (PGMs) and hazardous substances such as heavy metals and organic matter. The extraction of PGMs from waste TWCs using hydrochloric acid (HCl) has been extensively researched. However, the addition of oxidizing agents like H2O2 and aqua regia is necessary to facilitate PGMs dissolution, which poses significant environmental and operational hazards. Hence, developing a green PGMs recovery process without oxidants is imperative. Previously, we investigated the process of Li2CO3 calcination pretreatment to enhance the leaching of PGMs from waste TWCs by HCl, focusing on the process and mechanism of Li2CO3 calcination pretreatment. In this study, we focused on the leaching process of HCl after pretreatment. Our investigation includes a detailed examination of leaching kinetics and mechanisms. The optimal leaching conditions were: leaching temperature of 150 °C, leaching time of 2 h, HCl concentration of 12 M, and liquid-solid ratio of 10 mL/g. The experiments resulted in maximum leaching rates of about 96%, 97%, and 97% for Pt, Pd, and Rh, respectively. However, given the presence of heavy metals, attention needs to be paid to the harmless treatment of waste acids and leaching residues. The Pt and Pd leaching process is controlled by a mixture of interfacial chemical reactions and internal diffusion, and dominated by internal diffusion, while the leaching process of Rh is controlled by interfacial chemical reactions. Li+ in Li2PtO3, Li2PdO2, and Li2RhO3 preferentially leached and underwent ion-exchange reactions with H+, promoting the dissolution of Pt, Pd, and Rh in HCl.

Excessive dietary L-tryptophan regulated amino acids metabolism and serotonin signaling in the colon of weaning piglets with acetate-induced gut inflammation.

L-Tryptophan (Trp) was shown to improve the gut barrier and growth of weaning piglets. However, whether excessive dietary Trp regulates amino acids (AAs) metabolism and gut serotonin (5-HT) homeostasis in piglets with gut inflammation is not clear yet. We hypothesize that excessive dietary Trp alleviates acetate-induced colonic inflammation and gut barrier damage in weaning piglets partially through the regulation of colonic AAs metabolism and 5-HT signaling. Fifty-four 21-day-old weaned piglets were divided into six groups: control, acetate, 0.2%Trp, 0.2%Trp + acetate, 0.4% Trp, and 0.4%Trp + acetate. Piglets were fed a basal diet supplemented with 0%, 0.2%, or 0.4% of Trp throughout the 12-day experiment. During days 0-7, all piglets had free access to diet and drinking water. On day 8, piglets were intrarectal administered with 10 mL of 10% acetate saline solution or 0.9% saline. During days 8-12, all piglets were pair-fed the same amount of feed per kg bodyweight. Results showed that excessive dietary Trp alleviated acetate-induced reductions in daily weight gain and increase in feed/gain ratio. Trp restored (P < 0.05) acetate-induced increase in concentrations of free aspartate, glutamate/glutamine, glycine, 5-HT, and 3-methylindole in the colon, downregulation of zonula occludens-1 and 5-HT reuptake transporter (SERT) expression and upregulation of IL-1ß, IL-8, TLR4, and 5-HT receptor 2A (HTR2A) expression, and the increase in ratios of p-STAT3/ STAT3 and p-p65/p65 in the colon. The above findings suggested that excessive dietary Trp in the proper amount regulated colonic AAs metabolism, 5-HT homeostasis, and signaling that may contribute as important regulators of gut inflammation during the weaning transition.

Hydroxyproline Attenuates Dextran Sulfate Sodium-Induced Colitis in Mice: Involvment of the NF-κB Signaling and Oxidative Stress.

SCOPE: Inflammatory bowel disease (IBD) is a chronic disease of gastrointestinal tract in which oxidative stress and overactivation of inflammatory response are implicated. The aim of the present study is to test the hypothesis that hydroxyproline (Hyp), an amino acid with an antioxidative property, attenuates dextran sulfate sodium (DSS)-induced colitis in mice. METHODS AND RESULTS: Male C57BL/6 mice supplemented with or without 1% Hyp are subjected to 2.5% DSS in drinking water to induce colitis. Hyp attenuates the severity of colitis as evidenced by reduced disease activity index scores, decreased myeloperoxidase activity, histological damage, and apoptosis. Furthermore, DSS-induced increases in reactive oxygen species accumulation, TNF-α and IL-6 secretion, and malonyldialdehyde activity and a decrease in reduced glutathione in the colon are ameliorated by Hyp. The enhanced phosphorylation of STAT3 and NF-κB following DSS administration is mitigated by Hyp, which is also observed in LPS-treated RAW264.7 macrophages. Moreover, the inhibitory effect of Hyp on IL-6 expression is mainly mediated by the NF-κB signaling, because the induction of STAT3 and IL-6 by LPS is markedly reversed by Bay11-7085, a specific inhibitor NF-κB. CONCLUSION: In summary, Hyp is a critical nutrient with an ability to attenuate DSS-induced colonic damage in mice. This beneficial effect of Hyp is partially mediated by inhibiting the NF-κB/IL-6 signaling and the restoration of redox homeostasis.

Application of Single Voxel 1H Magnetic Resonance Spectroscopy in Hepatic Benign and Malignant Lesions.

BACKGROUND To quantify the metabolite changes in hepatic tumors by single-voxel 1H magnetic resonance spectroscopy (MRS) at 3.0 T and explore the application value of 1HMRS in the diagnosis of hepatic benign and malignant lesions. MATERIAL AND METHODS A total of 45 patients (55 lesions) diagnosed with hepatic lesions by ultrasound and/or computer topography (CT) from November 2006 to March 2007 were included in this study. All patients underwent 3D-dynamic enhanced scan with liver acquisition with acceleration volume acquisition (LAVA) sequence and single-voxel 1HMRS imaging with PRESS (point-resolved spectroscopy) sequence. The metabolite concentrations such as choline (Cho) and lipids (Lip) were measured. RESULTS There was significant difference regarding the occurrence rate of the obvious elevated Cho peaks between benign and malignant tumors (7/27 vs. 21/28, p=0.000). There was statistical significant differences regarding the Cho/Lip ratios in hepatic benign (0.0686±0.0283, 95% CI: 0.0134-0.1245) and malignant (0.1266 ±0.1124, 95% CI: 0.0937-0.2203) lesions (p<0.05). When compared with the pathological results, the sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were 85.7% (24/28), 92.6% (25/27), 92.3% (24/26), 86.2% (25/29), and 89.1% (49/55) respectively for the MRI assessment, and 92.6% (26/28), 88.9% (24/27), 89.7 (26/29), 92.3 (24/26), and 90.9% (50/55) respectively for 1HMRS combined with MRI assessment. CONCLUSIONS Single Cho peaks or Lip peaks cannot be used for the diagnosis of hepatic benign and malignant lesions. Combined use of 1HMRS and MRI can greatly improve the application value of MRI assessment in the diagnosis of hepatic benign and malignant lesions with a higher sensitivity, negative predictive value, and overall accuracy.