Effect of ammonium sulfate on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation

Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ calculation,X-ray photoelectron spectroscopy(XPS)analysis,time of flight secondary ion mass spectrometry(ToF-SIMS)analysis,and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate((NH_(4))_(2)SO_(4))on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation.The results showed that(NH_(4))_(2)SO_(4)exhibited a positive influence on hemimorphite sulfidation flotation.It was ascribed to the number of zinc components in the form of Zn^(2+)and[Zn(NH_(3))_(i)]^(2+)(i=1–4)increased in the flotation system after hemimorphite treatment with(NH_(4))_(2)SO_(4),which was beneficial to its interaction with sulfur species in solution,resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface.[Zn(NH_(3))_(i)]^(2+)participated in the sulfidation reaction of hemimorphite as a transition state.In addition the sulfidation reaction of hemimorphite was accelerated by(NH_(4))_(2)SO_(4).Thus,(NH_(4))_(2)SO_(4)presents a vital role in promoting the sulfidation of hemimorphite.

Adsorption characteristics of Pb(Ⅱ)ions on sulfidized hemimorphite surface under ammonium sulfate system

In this work,the effect of ammonium sulfate on the adsorption characteristics of low-concentration Pb(Ⅱ)ions on the sulfidized hemimorphite surface was comprehensively investigated.The results showed that ammonium sulfate could increase the maximum recovery of hemimorphite from 69.42%to 88.24%under a low concentration of Pb(Ⅱ)ions.On the hemimorphite surface pretreated with ammonium sulfate,the adsorption of Pb(Ⅱ)ions was enhanced and the main species of Pb adsorbed was changed from Pb―O/OH to PbS.This was due to the larger amount of ZnS providing more effective adsorption sites for Pb components to generate Pb S.Meanwhile,the intensity of ZnS decreased with the formation of PbS,demonstrating that ZnS was covered by PbS which formed later on the mineral surface.It was beneficial for the adsorption of butyl xanthate on the hemimorphite surface to form more hydrophobic substances.As a result,ammonium sulfate played a crucial role in realizing the efficient recovery of hemimorphite.

Thermodynamics and kinetics of extracting zinc from zinc oxide ore by the ammonium sulfate roasting method

Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by （NH4）2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and （NH4）2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows： 1 - （1 - α）1/3 = 30.85 exp（-45.57/RT）·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.

Recovery of valuable metals from a low-grade nickel ore using an ammonium sulfate roasting-leaching process

Metal leaching from a low-grade nickel ore was investigated using an ammonium sulfate roasting-water leaching process. The nickel ore was mixed with ammonium sulfate, followed by roasting and finally leaching with water. During the process the effects of the amotmt of ammonium sulfate, roasting temperature, and roasting time on the leaching recovery of metal elements were analyzed. The optimum technological parameters were determined as follows： ammonium sulfate/ore ratio, 0.8 g/g; roasting temperature, 400℃; and roasting time, 2 h. Under the optimum condition the leaching recoveries ofNi, Cu, Fe, and Mg were 83.48%, 76.24%, 56.43%, and 62.15%, respectively. Furthermore, the dissolution kinetics of Ni and Mg from the nickel ore was studied. The apparent activation energies for the leaching reaction of Ni and Mg were 18.782 and 10.038 kJ.mo1-1, which were consistent with the values of diffusion control reactions. Therefore, the results demonstrated that the leaching recoveries of Ni and Mg were controlled by diffusion.

Thermodynamics and kinetics of alumina extraction from fly ash using an ammonium hydrogen sulfate roasting method

A novel method was developed for extracting alumina （Al2O3） from fly ash using an ammonium hydrogen sulfate （NH4HSO4） roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1：8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-（2/3）α-（1-α）2/3=0.0374t exp[-16627/（RT）], whereαis the extraction rate and t is the roasting temperature.

Joint enhancement of lead accumulation in Brassica plants by EDTA and ammonium sulfate in sand culture

When EDTA was added alone in the Pb\|contaminated sand, the plant biomass and the total Pb amount in plant decreased in both species, Brassica pekinensis and B. juncea var. multiceps, though the shoot Pb amount increased. In contrast, when (NH 4) 2SO 4 was added alone in the Pb\|contaminated sand, little effect was observed on the shoot Pb amount, though the root Pb amount was significantly increased in B. juncea var. multiceps. When amending EDTA and (NH 4) 2SO 4 in combination, however, the shoot Pb amount in both species substantially increased, being, on an average, 2 times and 9 times higher than that in EDTA alone or (NH 4) 2SO 4 alone amended treatment, respectively. The two amendments showed antagonism for plant growth, but synergism for Pb bioaccumulation. B. pekinensis showed its highest level of shoot and total Pb amount in the treatment amended with EDTA and (NH 4) 2SO 4 only a half as much as in the other treatments. It is inferred that the mechanisms responsible for the joint\|enhanced Pb accumulation might be concerned with the acidification of the growth medium, cation exchange reaction and relieving EDTA induced toxicity as results by amending ammonium sulfate.

Atmospheric Corrosion of Steel A3 Deposited with Ammonium Sulfate and in the Presence of Sulfur Dioxide

A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).

Role of ammonium sulfate in sulfurization flotation of azurite:Inhibiting the formation of copper sulfide colloid and its mechanism

In this study,the role of(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)prior to sulfurization decreased the formation of colloid in flotation pulp,and the floatability of the suppressed azurite caused by excess sodium sulfide was restored.After adding(NH_(4))_(2)SO_(4)prior to sulfurization,the formation of Cu(NH_(3))_(n) ^(2+)intermediate products changed the path of the sulfurization reaction,which slowed the direct impact of HSon the azurite surface.The nucleation rate was reduced,and the growth of copper sulfide crystal was improved.Covellite(syn,CuS)with larger crystal grains was formed on the azurite surface,thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface.Therefore,the generated copper sulfide colloid significantly reduced,ultimately promoting the effective adsorption of xanthate on the azurite surface.

Recovery of valuable metals from waste diamond cutters through ammonia–ammonium sulfate leaching

Copper and zinc were recovered from waste diamond cutters through leaching with an ammonia–ammonium sulfate system and air as an oxidant. The effects of experimental parameters on the leaching process were investigated, and the potential–pH(E–pH) diagrams of Cu–NH_3–SO_4^(2-)–H_2O and Zn–NH_3–SO_4^(-2)–H_2O at 25°C were drawn. Results showed that the optimal parameters for the leaching reaction are as follows: reaction temperature, 45°C; leaching duration, 3 h; liquid-to-solid ratio, 50:1(mL/g); stirring speed, 200 r/min; ammonia concentration, 4.0 mol/L; ammonium sulfate concentration, 1.0 mol/L; and air flow rate, 0.2 L/min. The results of the kinetics study indicated that the leaching is controlled by the surface chemical reaction at temperatures below 35°C, and the leaching is controlled by diffusion through the product layer at temperatures above 35°C.

Extraction of Caprolactam from Aqueous Ammonium Sulfate Solution in Pulsed Packed Column Using 250Y Mellapak Packings

Liquid-liquid equilibrium (LLE) data of water-caprolactam-benzene-(NH4)2SO4 system at 303 K were measured for extraction of caprolactam from aqueous ammonium sulfate solution. The influence of fluid flow rate, pulsation intensity on flooding velocity and mass transfer was studied for extraction of caprolactam from ammonium sulfate solution in a laboratory pulsed packed column. The flooding velocities and overall apparent height of a transfer unit were given under various operation conditions. An industrial column developed based on above study is operated well. The scale-up effect is discussed.

Large scale preparation of phycobiliproteins from <i>Porphyra yezoensis</i>using co-precipitation with ammonium sulfate

The purpose of this study was to extract phyco-biliproteins (PBP) from Porphyra yezoensis using an optimized procedure and further establish a large scale process for protein production. According to our previous experiences on the extraction of PBP, salting out methods, e.g. ammonium sulfate precipitation, worked more efficiently than isoelectric precipitation, differential centrifugation or ultrafiltration. Thus, we chose ammonium sulfate to coprecipitate PBP in crude solution. After four times of precipitation followed by one time of high speed centrifugation, the maximum purity of crude phycoerythrin and phycocyanin reached 1.94 (A565/A280) and 0.85 (A615/A280), with a yield of 0.50% and 0.37%, respectively. A total of 0.94 mg phycoerythrin and 0.54 mg phycocyanin with purity of more than 3.2 were obtained from 1 g dried P. yezoensis after additional chromatography. We further scaled up the frozen dried P. yezoensis from 20 g to 400 g, with 1295 mg phycoerythrin and 593 mg phycocyanin obtained.

INVESTIGATION OF BEHAVIOR OF AMMONIUM SULFATE ON SURFACE OF IRON OXIDE Rong Sheng LI~*, Jing Feng CHEN, Hun YANG, Wu Yang ZHANG Dept. of Chemistry, Jilin University, Changchun 130023,

hhen ammonium sulfate-iron oxide is treated below 573 K, ammonium sulfate can spontaneously desperse on the surface of iron oxide. Simultaneously ammonium sulfate decomposes to some extent. During or after the dispersion, sulfate ion can interact with Fe atom on the surface of iron oxide to form a sort of surface sulfato complex of Fe and thus is transformed from the isolated into the bidentately bound form. Above 573 K the sulfato complex of Fe will gradually decompose with a further increase in temperature.

Physicochemical Study on the Interface Zone of Concrete Exposed to Different Sulfate Solutions

This paper reports the results of the visual observations and micro-analysis of concrete core samples after 6 and 12 months of their exposure to sodium, ammonium and magnesium sulfate solutions with the same concentration of sulfate ions. XRD, SEM and EDS were used for micro-analysis of the mi-crostructure and the composition of the interface zone in the samples. The results indicate that the deterioration of concrete by different sulfate solutions could proceed differently with regard to the mechanism and the mode of damage caused. The damage of concrete exposed to sodium sulfate solution is mainly caused by the gypsum crystals formed in the interface zone, which lead to expansion and cracking. In the case of concrete immersed in magnesium sulfate solutions, a layer of brucite (magnesium hydroxide) and gypsum was produced in the interface zone, which reduces the cohesiveness of the interface zone in concrete. For the concrete immersed in ammonium sulfate solutions, the conversation of mortar to some mush mass by ammonium ions and the formation of a large of gypsum occurred in the interface zone, consequently, serious softening of hydrated cement pastes and expansion and cracking of concrete are the characteristics of the attack by ammonium sulfate solutions. Also, it is considered that using drilled concrete core as samples to evaluate the sulfate resistance of concrete is a good and accelerated method.

废低温脱硝催化剂热处理除硫铵盐研究

废低温脱硝催化剂表面被硫酸氢铵覆盖,会严重影响脱硝催化剂的使用活性,而且在再生水洗过程中,硫酸氢铵会影响废脱硝催化剂的物理强度。由此,本文研究了在水洗前增加高温煅烧工艺,去除废低温脱硝催化剂中的部分硫酸氢铵,以保证废低温脱硝催化剂再生的顺利进行。

高盐废水中硫酸铵和硫酸钠的分质结晶工艺研究

处理高盐废水并回收其中的盐资源是许多生产企业废水综合治理的难题。采用等温溶解平衡法测定了10、15、60、80℃下Na_(2)SO_(4)-(NH_(4))_(2)SO_(4)-H_(2)O的液固相平衡数据,基于相平衡数据划分了结晶区域。根据高盐废水的组成和液固相平衡数据,提出了分质结晶分离(NH_(4))_(2)SO4和Na_(2)SO_(4)的工艺路线,设计了结晶过程工艺参数并进行了实验验证。结果表明,废水经3步结晶回收得到的(NH4)2SO4纯度达到了99.2%、Na_(2)SO_(4)纯度达到了98.9%,满足GB/T 535—2020《肥料级硫酸铵》和GB/T 6009—2014《工业无水硫酸钠》的纯度指标要求。该研究可为高盐废水中(NH_(4))_(2)SO_(4)和Na_(2)SO_(4)的回收利用提供参考。

硫酸亚铁铵活化过硫酸钠降解土壤吡虫啉的研究

为探究硫酸亚铁铵与过硫酸钠对土壤中吡虫啉降解率的影响,实验设定两种降解试剂添加量均为0.2、0.5、1.0 mmol,土壤中吡虫啉质量浓度为33.0、49.5、66.0μg/g,农作物土壤为水稻、玉米与茶叶土壤,温度为-4、25℃。结果表明:1.0 mmol过硫酸钠与0.2 mmol硫酸亚铁铵对水稻土壤中吡虫啉的降解率最佳,最高可达98.8%,且前120 min内降解速率较快。3种吡虫啉浓度的降解效果没有显著差异(p>0.05);温度对降解率的影响不显著(p>0.05)。土壤中有机碳与pH越低,越有利于过硫酸钠与硫酸亚铁铵降解土壤中吡虫啉。

大气氨气污染特征分析及其对PM_(2.5)二次无机组分的影响

为研究大气中氨气的污染特征及其对细颗粒物(PM_(2.5))二次无机组分的影响,于2021—2022年在江苏省南京、无锡、镇江、常州、徐州5个城市同期开展氨气及气溶胶组分的在线监测,并采用热动力学稳态模型(ISORROPIA)评估氨气的减排成效。结果表明,5个城市氨气年均质量浓度为10.1μg/m^(3),5个城市年均质量浓度为7.7~15.2μg/m^(3),其中徐州最高,南京最低。总氨于夏季(6月)达到浓度峰值,受温度及硝酸铵的热不稳定性影响,氨气在12:00左右出现浓度峰,而铵盐则呈现出昼低、夜高的日变化特征。5个城市均处于富氨水平,全年气溶胶呈中性,氨气中和额外酸性气体的潜力较为突出。冬季江苏省各市只有通过大幅度的氨减排(>60%)才能使PM_(2.5)浓度显著下降,而对二氧化硫(SO_(2))、氮氧化物(NO_(X))进行减排才能更加高效地减轻PM_(2.5)污染。

离子吸附型稀土矿区硫酸铵原位浸矿与淋洗过程的室内模拟

离子吸附型稀土尾矿中残留的大量硫酸铵浸矿剂随雨水淋滤进入周边环境,可造成矿区及周边土壤和水体严重污染。本研究通过实地采集稀土矿区土壤,开展室内一维土柱实验分别模拟浸矿过程和淋洗过程,并建立Hydrus-1D模型,评价该模型对稀土矿浸矿和淋洗过程的模拟性能。Hydrus-1D模型的弥散度的率定值为0.5 cm,浸矿与淋洗过程的K d的率定值分别为0.07 cm^(3)/g和1.2 cm^(3)/g;在浸矿过程模拟中,4个观测孔模型的R^(2)为0.95~0.99,E_(RMS)为1.3~6.8 mmol/L;淋洗过程的R^(2)为0.93~0.98,E_(RMS)为0.2~1.6 mmol/L;Hydrus-1D能够较好模拟浸矿和淋洗过程中NH_(4)^(+)的迁移行为。示踪实验中Cl^(-)穿透耗时为30~90 min;浸矿实验中,4个观测孔达到吸附饱和耗时为60~150 min;淋洗实验中,4个观测孔的NH_(4)^(+)浓度低于检测限的耗时为360~540 min;土壤吸附作用对浸矿与淋洗过程中NH+4运移过程的影响显著。

石灰石法与氨法脱硫产物中痕量元素对比

为实现脱硫产物资源化利用,评估硫酸铵和脱硫石膏的环境风险,分析了全厂重金属的含量,研究了石膏和硫酸铵中重金属的赋存和浸出特性。结果表明:Cu、Cr在硫酸铵中的含量均不足1%,远低于在石膏中的含量;Mn、Sn在石膏和硫酸铵中的含量相差6倍以上,可能是因为Mn、Sn离子的弱酸性;As、Pb含量在不同炉型的石膏中相差5倍以上,Se、Cd、Ba的分布规律不受炉型和脱硫工艺的影响;Cr的浸出质量浓度最高,约为标准限值的2.04%,Se与石膏中的Ca^(2+)生成CaSeO_(3)沉淀,Cu以CuFe_(2)O_(4)形式赋存于石膏中;硫酸铵中重金属的整体浸出水平高于脱硫石膏,但实验过程中重金属的排放和浸出质量浓度均远低于我国现行标准限值,脱硫产物资源化利用安全可行。

细菌素纯化技术及其应用研究进展

细菌素是一种由细菌在核糖体内合成并释放到胞外,具有抑菌或杀菌效果的多肽。大量研究表明细菌素具有调节肠道微生物种群、抗炎和抗癌等作用。然而,细菌素纯化成本高、产量低且存在一定环境污染是限制细菌素广泛应用的重要因素。提高细菌素的纯化倍数和回收率是其纯化的关键,增加细菌素的比活力和产量对其生产应用至关重要。合理选择纯化技术,可以有效提高细菌素的产量、纯度和回收率。由于细菌素的分子量和带电荷性质具有差异性,应根据其特性选择不同的纯化技术。细菌素的纯化包括粗分离纯化和精细分离纯化,粗分离纯化技术包括硫酸铵沉淀法、有机溶剂萃取法、大孔树脂法和透析法,精细分离纯化技术包括离子交换层析法、凝胶过滤层析法、反相高效液相色谱法等。广泛应用的细菌素纯化技术包括硫酸铵沉淀、离子交换层析、凝胶过滤层析和反相高效液相色谱等,并且由这几种技术组合的两步法和三步法纯化技术近几年应用较多。近年来,快速蛋白液相色谱等非传统的纯化技术逐渐应用于细菌素的精细分离纯化。高效、低成本、无污染、绿色环保的细菌素纯化技术是其进一步研究的关键,这些技术难点的突破将为细菌素在医疗领域中的应用奠定基础。本文对细菌素的纯化技术及其应用进行归纳分析,可为细菌素的进一步开发与应用提供参考。