Recovering phosphate ore at low temperatures poses a challenge. In this work, non-ionic surfactant triethanolamine oleate (TOAM) was used as a novel cryogenic collector for the separation of hematite and Fluorapatite (FAP). The flotation test results indicated that under the conditions of TOAM at 100 mg/L, starch at 13 mg/L, and pH 9, it achieved good recovery rate and grade of FAP concentrate in the mixed ore of 88.74 % and 35.32 %. Especially under low temperature conditions (15degree celsius), the recovery rate of TOAM as collector was 29.36 % higher than that of NaOL. This was mainly due to the significantly higher low-temperature solubility of TOAM compared to NaOL. The adsorption mechanism of TOAM on the surface of FAP was studied through PBAI, FTIR, XPS tests, and DFT calculations. The results indicated that TOAM can significantly enhance the hydrophobicity of the FAP surface, primarily through hydrogen bonding and electrostatic interactions. The results of the DFT calculations also confirmed that the hydrogen bonding between the -OH functional group on the TOAM molecule and the O active site on the FAP surface, along with the electrostatic interactions, were the main adsorption mechanisms. This work can provide some guidance for the application of non-ionic collectors in low-temperature flotation. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and

Although alternatives to mercury (Hg) are available in most products and industrial activities, Hg continues to be an ingredient in some products, including fluorescent lamps and electrical and electronic equipment (EEE). In this work, low-cost passive air samplers (PASs) were used to investigate the atmospheric Hg pollution in Zhongshan, a large industrial city and major hub of mercury-added product manufacturing in South China. The GEM concentrations in the atmosphere were measured for two weeks during the summer of 2019 at a total of 144 sites across Zhongshan. Comparison with the results of active sampling confirmed that the PASs yielded accurate and reliable gaseous elemental mercury (GEM) concentrations and were thus well-suited for multi-site field monitoring. The mean GEM concentrations in the areas with mercury-added product manufacturing activities (5.1 +/- 0.4 ng m-3) were significantly higher than those in other parts of Zhongshan (1.5 +/- 0.4 ng m-3), indicating that local releases, rather than regional transport, were responsible for the atmospheric Hg pollution. Elevated GEM concentrations (up to 11.4 ng m-3) were found in the vicinity of fluorescent lamp and EEE factories and workshops, indicating significant Hg vapor emissions, presumably from the outdated production technologies and non-standard operation by under-trained workers. The Hg emissions from mercury-added product manufacturing were estimated to be 0.06 and 7.8 t yr-1 for Zhongshan and China, respectively, based on the scales of fluorescent lamp and EEE production. The non-carcinogenic health risk of Zhongshan residents from inhalation and ingestion was judged acceptable, whereby the inhalation exposure in Hg-polluted areas exceeded that of dietary ingestion. These findings demonstrate that mercury-added product manufacturing still contributes notably to anthropogenic gaseous Hg releases in the industrial areas with intense mercury-added product manufacturing activities.

Due to the lack of a priori knowledge on true source makeup and contributions, whether the source apportionment results of Unmix and positive matrix factorization (PMF) are accurate cannot be easily assessed, despite the availability of built-in indicators for their goodness of fit and robustness. This study systematically evaluated, for the first time, the applicability and reliability of these models in source apportionment of soil heavy metal(loid)s with synthetic datasets generated using known source profiles and contributions and a real-world dataset as well. For eight synthetic datasets with different pollution source characteristics, feasible Unmix solutions were close to the true source component compositions (R2 > 0.936; total mean squared errors (MSEs) < 0.04), while those of PMF had significant deviations (R2 of 0.484-0.998; total MSEs of 0.04-0.16). Nonetheless, both models failed to accurately apportion the sources with collinearity or non-normal distribution. Unmix generally outperformed PMF, and its solutions showed much less dependence on sample size than those of PMF. While the built-in indicators provided little hint on the reliability of both models for the real-world dataset, their sample-size dependence indicated that Unmix probably yielded more accurate solutions. These insights could help avoid the potential misuse of Unmix and PMF in source apportionment of soil heavy metal(loid) pollution.

Although already eliminated in most industrial processes, mercury, as an essential ingredient in all energy-efficient lighting technologies, is still used in fluorescent lamp manufacturing. This study was conducted to investigate the atmospheric pollution caused by fluorescent lamp production and assess the associated public health risk in a large industrial and commercial city of south China, Zhongshan, which is a major production hub of lighting products. Concentrations of total gaseous mercury (TGM) in the atmosphere were measured over a total of 342 sites in the industrial, commercial, and residential areas. The average levels of TGM in the industrial, commercial, and residential areas prior to the landing of a typhoon were 12 +/- 11, 3.6 +/- 2.1, and 2.7 +/- 1.3 ng.m(-3), respectively. TGM concentrations in the industrial areas exhibited significant diurnal variation, with levels in the working hours being much higher than those in the non-working hours, which indicates that the high atmospheric mercury concentrations were contributed by local emissions, instead of regional transport. Most fluorescent lamp manufacturing activities in the city were shut down during a typhoon event, which resulted in a significant reduction in the average TGM level (down to 1.6 +/- 1.8 ng.m(-3)) and rendered the difference in the average TGM levels in the industrial areas no longer significant between the working and non-working hours. Elevated TGM levels (up to 49 ng.m(-3)) were found near clusters of small-scale fluorescent lamp workshops in both industrial and commercial areas, which is indicative of significant emissions of mercury vapor resulting from obsolete equipment and production technologies. No significant non-carcinogenic risk was found for the general residents in the sampling area over the study period, while the risk for the workers in the fluorescent lamp manufacturing facilities and workshops could be higher. These findings indicate that fluorescent lamp manufacturing in the developing countries is a major source of atmospheric mercury. (C) 2020 Elsevier Ltd. All rights reserved.