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The low-grade zinc oxide ore was sulfidized to increase the efficiency of flotation, but the effect of pre-sulfidization on the adsorption mechanism of octadecyl amine (ODA) on the smithsonite surface is currently unclear. In this study, the effect of pre-sulfidization on the adsorption mechanism of ODA and the flotation behavior was studied using smithsonite and pre-sulfidized smithsonite as the samples by zeta potential, contact angle measurement, total organic carbon analyzer (TOC), quartz microcrystalline balance (QCM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and micro-flotation tests. Micro-flotation tests showed that the pretreatment of sulfidization could improve the floatability of smithsonite. Zeta potential and contact angle measurements demonstrated that pre-sulfidization could favor the adsorption of ODA, which is further confirmed by the adsorption tests of ODA using TOC and QCM. Furthermore, FTIR and XPS analysis showed that pre-sulfidization changes the adsorption mode of ODA, changing it from physical adsorption to chemical adsorption. These results suggested that the favorable effect of pre-sulfidization on the adsorption of ODA and the flotation of smithsonite might provide important guidance for industrial application.

Aeromonas salmonicida is an important pathogen that causes furunculosis in trout and salmon with high morbidity and mortality, resulting in significant economic losses in aquaculture. Overuse of antibiotics has led to the continuous emergence of drug-resistant strains. Hence, there is an urgent need to find an alternative environmentally friendly antimicrobial agent. In this study, we isolated a virulent phage of A. salmonicida, named ASG01, which belongs to the Myoviridae family and maintains lytic activity at a pH value range from 4 to 12 and in the temperature range from 30 °C to 60 °C. The whole genomic sequence of ASG01 showed 82% similarity to Aeromonas phage pAh6-C. The cell wall hydrolase (Cwh)-encoding gene from the genome of ASG01 was predicted and heterologously expressed. Notably, in the absence of additional phage genes, endogenous expression of Cwh could lyse E. coli cells and greatly inhibit the growth of tested fish pathogenic bacteria. The lytic activity of Cwh was eliminated when the predicted active site was mutated. These results indicate that Cwh of ASG01 possessed excellent lytic activity and a wide antibacterial spectrum, suggesting its potential as an effective enzybiotic.

As the world’s largest farmed marine animal, oysters have enormous economic and ecological value. However, mass summer mortality caused by high temperature poses a significant threat to the oyster industry. To investigate the molecular mechanisms underlying heat adaptation and improve the heat tolerance ability in the oyster, we conducted genome-wide association analysis (GWAS) analysis on the F2 generation derived from the hybridization of relatively heat-tolerant Crassostrea angulata ♀ and heat-sensitive Crassostrea gigas ♂, which are the dominant cultured species in southern and northern China, respectively. Acute heat stress experiment (semi-lethal temperature 42 °C) demonstrated that the F2 population showed differentiation in heat tolerance, leading to extremely differentiated individuals (approximately 20% of individuals die within the first four days with 10% survival after 14 days). Genome resequencing and GWAS of the two divergent groups had identified 18 significant SNPs associated with heat tolerance, with 26 candidate genes located near these SNPs. Eleven candidate genes that may associate with the thermal resistance were identified, which were classified into five categories: temperature sensor (Trpm2), transcriptional factor (Gata3), protein ubiquitination (Ube2h, Usp50, Uchl3), heat shock subfamily (Dnajc17, Dnaja1), and transporters (Slc16a9, Slc16a14, Slc16a9, Slc16a2). The expressional differentiation of the above genes between C. gigas and C. angulata under sublethal temperature (37 °C) further supports their crucial role in coping with high temperature. Our results will contribute to understanding the molecular mechanisms underlying heat tolerance, and provide genetic markers for heat-resistance breeding in the oyster industry.

The most common beneficiation method for feldspar is flotation with a cationic (amine) collector under acidic conditions. However, there are several disadvantages to this, such as environmental pollution and equipment corrosion. In order to resolve such problems, it is important to study the flotation of feldspar using anionic collectors under natural pH conditions. The purpose of this paper is to study the effects and mechanism of Fe3+ on flotation separation of feldspar and epidote using sodium oleate (NaOL) at a natural pH. Through flotation experiments, adsorption measurements, zeta potential testing, FTIR analysis and X-ray photoelectron spectroscopy (XPS), the mechanism of Fe3+ on the surface of feldspar and epidote is revealed, and the reason behind the difference in flotation of the two minerals is discussed. The flotation test results show that Fe3+ can significantly improve the flotation behavior of minerals when NaOL is used as a collector under natural pH, and the highest recovery rates of feldspar and epidote are 90% and 43%, respectively. Analysis of the solution and adsorption measurement results show that Fe3+ is adsorbed on the minerals′ surface in the form of Fe(OH)3, which promotes the adsorption of NaOL on the minerals’ surface through Fe(OH)3, activating the flotation of feldspar and epidote. The difference in adsorption of Fe3+ between feldspar and epidote is the reason for this difference in flotation behavior. The results of the zeta potentials show that after being treated with Fe3+, the electrostatic adsorption of NaOL displays a significant negative shift on the surface of feldspar, while there is almost no electrostatic adsorption of NaOL on the surface of Fe3+-treated epidote. FTIR analysis confirmed that the difference in the adsorption of Fe3+ and NaOL on the surface of feldspar and epidote is due to the fact that there are more active particles (metal bonds) on the surface of feldspar than on the surface of epidote, and the properties of these metal bonds can be changed by Fe3+, which allows NaOL to be more easily adsorbed on the mineral surface through –COO−. The possible adsorption form is “mineral-Fe3+–COO−“. Compared with the infrared spectrum of epidote, there is a new absorption peak at 1713.68 cm−1, which can be attributed to the C=O characteristic peak of NaOL in the infrared spectrum of Fe3+–NaOL-treated feldspar, which is why the floatability of feldspar is better than epidote. XPS confirmed that the Fe on the surface of feldspar is Fe3+ in the form of Fe(OH)3, while Fe on the surface of epidote is mainly Fe2O3 (Fe–O) contained in mineral crystals. Furthermore, there is less adsorption of Fe3+ on the surface of epidote, and this discrepancy leads to the difference in the adsorption of NaOL on the minerals’ surface, which itself leads to the difference in flotation behavior between feldspar and epidote. These findings indicate that the flotation separation of feldspar and epidote can be achieved using Fe3+ and NaOL under natural pH. This study may provide a reference for the flotation mechanism of feldspar and epidote under natural pH.

Chlorite and serpentine are common magnesium-containing gangue minerals in copper sulfide flotation. In this study, sodium alginate, a natural hydrophilic polysaccharide, was introduced as a selective depressant for these gangue minerals. Micro-flotation tests were conducted on both single minerals and synthetic mixtures. The flotation results showed that sodium alginate could simultaneously depress the flotation of chlorite and serpentine effectively, but seldom influenced the floatability of chalcopyrite at pH 9. In the ternary mixture flotation, a concentrate with a Cu grade of 31% could be achieved at Cu recovery of 90%. The selective depression of chlorite and serpentine was also validated by the real ore flotation experiments. The selective depression mechanism was investigated through adsorption tests, zeta potential measurements, and FTIR analyses. The adsorption density results implied that sodium alginate selectively adsorbed on the surface of phyllosilicates, but no adsorption on the chalcopyrite surface was observed. The zeta potential results showed that the sodium alginate could selectively decrease the surface charge of chlorite and serpentine. The FTIR results revealed the chemical adsorption of sodium alginate on the chlorite and serpentine surface and no form of adsorption on chalcopyrite, agreeing well with the adsorption density results. On the basis of these results, a selective adsorption model of sodium alginate on the mineral surface was proposed.

A novel method to limit the adverse effect of fine serpentine on the flotation of pyrite was investigated in this paper. The flotation results showed that coarser serpentine possessed a weaker depression effect on the pyrite flotation process, and the use of KAl(SO4)2·12H2O could efficiently limit the detrimental effect of fine serpentine on pyrite with a maximum increase of pyrite recovery from 14% to 86% at pH 9.0. The results of particle size measurements and rheological measurements exhibited that the addition of KAl(SO4)2·12H2O increased the particle size of serpentine buta hrdly affected the particle size of pyrite, then limited the formation of serpentine-pyrite aggregates. Adsorption test results showed that the adsorption density of potassium butyl xanthate (PBX) onto pyrite regained with the addition of KAl(SO4)2·12H2O, thereby achieving good flotation improvement. It can be concluded that KAl(SO4)2·12H2O is likely to be an effective pyrite flotation reagent, especially in the presence of fine serpentine.

A nickel-copper sulfide system usually coexists with serpentine in deposits. Low nickel-copper recovery and high content of serpentine in concentration adversely affects subsequent metallurgical processes. In this study, test data showed different rheological results at various densities. When the solid ratio of sulfide to serpentine was 1:1, lower pulp density (20 wt %) contributed to better rheological and flotation outcomes. Generally, the addition of SHMP (sodium hexametaphosphate) is beneficial to reduce the amount of serpentine mineral into the concentration as a depressant through changing the surface electrical behavior of serpentine. However, the different dosages of SHMP have little impact on pulp rheology at 40 wt % of slurry, but there is a huge difference on flow property at 20 wt % pulp. The results revealed that rheology, which is caused by pulp density, played a key role in flotation performance. The decline in density (from 40 wt % to 20 wt %) increased the nickel and copper recoveries from 70.7% to 79.5% and 82% to 85.4% respectively in the artificial mixture (1:1). The content of serpentine in concentration decreased by around 20% by using SHMP at the same time.

In this study, the effect of sodium pyrophosphate (NaPP) on the separation of apatite from dolomite by flotation was systematically investigated. Flotation results revealed that NaPP could selectively depress the flotation of apatite, thus realizing the separation of apatite from dolomite. Further, the selective depression mechanism of NaPP was studied through zeta potential measurements, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results demonstrated that the adsorption of sodium oleate (NaOL) onto apatite surface was depressed by the preferential interaction of NaPP with active Ca sites. For dolomite, while the presence of NaPP hindered the interaction of NaOL with active Ca sites, it appeared to enhance the reactivity with active Mg sites. Thus, the adsorption of NaOL onto dolomite surface was hardly influenced. In this way, the separation of apatite from dolomite was achieved.

Fluorite is the principal mineral of fluorine and usually coexists with quartz in deposits. The removal of fine quartz in fluorite concentrate is the main problem in fluorite flotation. In this study, the flotation tests on fluorite, quartz and a weight equivalent mixture (all less than 10 μm) using water glass (with different modulus) as depressants and sodium oleate as collector were conducted. The mechanism of fine quartz entering the fluorite concentrate was investigated through optional observations and rheology measurements on the flotation pulp. The particle interactions between fine fluorite and quartz under flotation-related conditions were analyzed through zeta potential measurements and DLVO calculations. The results revealed that there existed strong hetero-coagulation between fluorite and quartz particles in the flotation pulp, which could be the main reason for the quartz entering the fluorite concentrate in the flotation process. Water glass with higher modulus could eliminate the hetero-coagulation more totally but inevitably influences the flotability of fluorite.