Boosting ammonia synthesis over molybdenum nitride through nickel-mediated nitrogen activation and hydrogen transfer

Synergistic optimization of nitrogen dissociation and hydrogen transfer might be an efficient strategy to develop a highly efficient ammonia synthesis catalyst. Herein, the Ni-modified molybdenum nitride is used as the catalyst of ammonia synthesis. The presence of the highly dispersed Ni metal results in enhancement of nitrogen vacancy, causing the acceleration of the exchange and reaction of the lattice N species with the nitrogen species from the gaseous phase. In addition, the presence of Ni species facilitates the hydrogen transfer and spillover, as well as easy hydrogen release. As a result, the optimized molybdenum nitride catalyst with 0.1 wt% Ni shows a 2.5-times higher catalytic activity than that of the catalyst without Ni species at 400°C owing to the coupling of nitrogen activation and hydrogen transfer effects. This general approach could inspire the rational design of other metal catalysts for ammonia synthesis.     

利用凹凸棒土制备废水氨氮吸附剂的研究

以凹凸棒土为主要原料,制备废水氨氮吸附剂,采用正交实验设计,考察了添加剂含量、焙烧温度、焙烧时间等因素对氨氮去除率的影响。结果表明,添加剂含量10%,焙烧温度500℃,焙烧时间1 h时,所制备的吸附剂性能指标最好,对废水中氨氮的去除率可达85%。     

碳酸钾改性油茶壳活性炭吸附水中氨氮的研究

利用所制备的油茶壳活性炭对水体中的氨氮进行了吸附,探讨了各因素对吸附效果的影响,并进行了吸附热力学和动力学分析。结果表明:活化温度及活化剂浓度的提高有利于油茶壳活性炭对氨氮的吸附。吸附过程在420 min左右达到平衡,符合准二级动力学模型。吸附过程符合Langmuir等温吸附模型,对氨氮的最大吸附量可达到10.83 mg/g。在最适的实验条件下,0.1 g的碳酸钾改性油茶壳活性炭对初始质量浓度为20 mg/L的氨氮废水中氨氮的去除率可以达到50.3%,吸附效果良好。     

氧化铈改性沸石脱氮的研究

用浸渍焙烧法制备稀土吸附剂,用于静态脱氮实验。结果表明,氧化铈改性的稀土吸附剂吸附性能优于氧化镧和氧化镧-氧化铈复合改性的稀土吸附剂;当吸附剂用量为2 g/L,进水pH为4~6,吸附时间为2.5 h,氧化铈改性稀土吸附剂对模拟废水氨氮浓度为20 mg/L的吸附率达到80.23%;吸附剂再生6次后氨氮的去除率下降不到7%,说明吸附剂具有较好的稳定性。     

改性膨润土对氨氮废水吸附性能的研究

用内蒙膨润土及其碱改性膨润土进行模拟氨氮废水的脱氮实验研究。结果表明,在氨氮溶液初始浓度为300 mg/L,pH值为3.0～7.0时,相对于天然膨润土,碱改性膨润土对氨氮的吸附量有了很大提高,其吸附等温线符合Freundlich和Langmuir方程,且对氨氮的吸附动力学符合准一级和准二级吸附动力学模型,说明化学吸附和物理吸附共同起作用;在应用于畜禽废水处理中,碱改性膨润土对氨氮去除率达到91.0%。     

超重力强化折点氯化法处理低浓度氨氮废水

折点氯化法具有反应速度快、氨氮脱除率高等优点,广泛应用于氯碱等行业中,但反应过程中产生二氯胺致使废水中余氯浓度过高,无法满足离子膜法烧碱生产安全技术规定（HAB004—2002）。为解决这一问题,本文提出了超重力技术强化折点氯化法处理氨氮废水的新工艺,利用超重力技术强化传质的特点,实现次氯酸钠和氨氮的快速反应以及二氯胺的有效去除,研究了超重力因子（β）、氯氮比（Cl/N）、pH和液体流量Q_L等操作参数对氨氮脱除率和余氯的影响规律。研究结果表明,当Cl/N=11、β=30、pH=6~8和液体流量Q_L=80L/h时,氨氮去除率＞95%,余氯浓度＜1.5mg/L。与传统反应器相比,二氯胺去除效果明显,处理后的水中氨氮满足烧碱安全生产技术规定,此方法对于氯碱行业中低浓度氨氮的去除具有广阔的应用前景。     

Simultaneous organic carbon and nitrogen removal in an SBR controlled at low dissolved oxygen concentration

Simultaneous organic carbon and nitrogen removal was studied in a sequencing batch reactor (SBR) fed with synthetic municipal wastewater and controlled at a low dissolved oxygen (DO) level (0.8 mg dm^?3). Experimental results over a long time (120 days) showed that the reactor achieved high treatment capacities (organic and nitrogen loading rates reached as high as 2.4 kg COD m^?3 d^?1 and 0.24 kg NH₃‐N m³ d^?1) and efficiencies (COD, NH₃‐N and total nitrogen removal efficiencies were 95%, 99% and 75%). No filamentous bacteria were found in the sludge even though the reactor had been seeded with filamentous bulking sludge. Instead, granular sludge, which possessed high activity and good settleability, was formed. Furthermore, the sludge production rate under low DO was less than that under high DO. Significant benefits, such as low investment and less operating cost, will be obtained from the new process. © 2001 Society of Chemical Industry     

改性球形活性炭对氨气吸附性能的研究

研究了不同金属盐溶液浸渍改性的球形活性炭对氨气的吸附性能以及同种浸渍剂的最佳浸渍比。采用扫描电镜、透射电镜、X射线衍射仪、康塔吸附仪探究了不同浸渍比对浸渍炭样品的表面形貌、物相结构及孔径分布的影响。通过固定床吸附装置对基炭和浸渍炭进行了氨气吸附性能的研究。结果表明：浸渍剂种类对氨气吸附效果有很大影响, 同等浸渍条件下, 氯化钴浸渍的活性炭具有最优氨气吸附效果, 氯化钴浸渍比为50%的样品对氨气的吸附量最高, 可达54.05 mg/mL, 为基炭的37倍。对吸附氨气后样品的物化性质进行分析以及程序升温脱附表征, 结果表明氯化钴与氨气反应生成了[Co（NH₃）₆]Cl₃。     

不同改性处理玉米秸秆对氨氮吸附性能研究

对比了酸改性、碱改性和接枝共聚改性对玉米秸秆吸附氨氮性能的影响。结果表明,当初始氨氮质量浓度为200 mg/L时,玉米秸秆经酸改性、碱改性和接枝共聚改性的最大氨氮平衡吸附量分别达到23.4、26.4、33.8 mg/g,较未改性时分别提高55.0%、74.8%和123.8%,改性吸附效果为接枝共聚改性碱改性酸改性。玉米秸秆对氨氮的吸附过程可用Langmuir和Freundlich吸附等温模型描述,符合伪二级动力学方程。经过改性处理后△G降低,对氨氮的吸附变得更加容易。     

改性玄武岩岩棉去除水中氨氮的实验研究

对废弃玄武岩岩棉通过改性去除水中氨氮进行了试验研究.探讨了几种因素对氨氮去除效果的影响和吸附机理.结果表明,酸、碱改性及烘箱、微波、超声波三种加热方法中,以采用超声波加热、质量分数为15%的盐酸改性的岩棉去除氨氮的效果最佳,当污水中氨氮的浓度为60mg/L左右时,改性岩棉用量为每1g/100mL,吸附时间为90min,pH为6的试验条件下,氨氯的去除率为25%以上,其吸附等温线符合Langmuir型.     

人造沸石对氨氮废水的吸附及其电化学再生研究

采用人造沸石对模拟氨氮废水进行吸附,并对其进行电化学再生,探讨了吸附及再生的影响因素。结果表明,最佳吸附条件:吸附时间为90 min,pH为中性或弱酸性,人造沸石投加量为120 g/L,在此条件下,氨氮去除率可达84%;最佳再生条件:电解时间为40 min,Na Cl浓度为0.1 mol/L,温度为50℃,pH为10,在此条件下,人造沸石再生率可达到97.48%。人造沸石重复使用6次后,再生率仍可达到88%以上。     

处理高浓度氨氮废水的阳离子交换树脂筛选

目前树脂种类繁多,给处理高浓度氨氮废水的树脂选型带来困难。根据离子交换理论,利用001×7、D61和D001三种阳离子交换树脂,模拟研究了氮肥厂废水（氨氮浓度为915 mg·L^-1）氨氮的吸附等温式,在30～50 min内三种树脂对氨氮的吸附基本可达到平衡,吸附等温线均符合Freundlich吸附模式;进而研究了这三种树脂对废水中氨氮吸附的选择性系数、工作交换容量和离子交换速率。结果表明,用D61树脂处理含高浓度氨氮的废水效果较为理想,可以相对较少的用量,使处理后水质达到相关排放标准的要求。     

Activated carbon from bacterial cellulose as an effective adsorbent for removing dye from aqueous solution

ABSTRACT

Novel activated carbon (AC) derived from bacterial cellulose (BC-AC) was produced by phosphoric acid activation at a carbonization temperature of 500 °C. BC-AC possesses mesoporous structures of 2.3 nm in diameter, porosity of 1.0 cm³/g and surface area of 1734 m²/g with high thermal stability between 100 and 500 °C. BC-AC could be used as an effective adsorbent for removing methylene blue (MB) from aqueous solutions with the maximum adsorption capacity of 505.8 mg/g. BC-AC presented physisorption and the adsorption of MB was most likely to be a monolayer adsorption. The Redlich–Peterson model displayed the best fit with the experimental data.     

改性凹凸棒石和沸石对氨氮废水吸附性能的研究

采用焙烧、钠化、酸化和碱化4种改性方法对天然凹凸棒石和沸石进行改性,其中碱化改性对氨氮吸附能力提高最大,研究了碱化样品的结构及对氨氮废水的吸附性能。结果表明,碱改性品在氨氮溶液初始浓度300 mg/L,pH值2.5~8.0时,对氨氮的吸附量较高;对氨氮的吸附等温线符合Freund lich和Langmu ir方程式。同时,对氨氮的吸附动力学符合准二级吸附动力学模型,并以化学吸附为主。用于畜禽废水处理中,对氨氮去除率最高达到87.6%。     

高浓度氨氮对活性污泥性能的影响

采用2个SBR反应器RUN1和RUN2在氨氮质量浓度分别为50、350 mg/L的条件下驯化污泥,考察氨氮浓度对污泥活性的影响;并在氨氮质量浓度分别为59、232、368、604和1 152 mg/L的条件下对2个反应器中的驯化污泥进行氨氮适应性试验。结果表明:在较高的氨氮浓度条件下,有机物降解菌对CODCr降解率下降约47%,硝化菌对氨氮的去除率下降约55%,脱氢酶活性下降约56.6%,显示出高浓度氨氮对有机物降解菌和硝化菌的活性都具有一定的抑制作用;当进水氨氮质量浓度从59 mg/L升至1 152 mg/L时,RUN1和RUN2中污泥对CODCr的去除率分别由89.2%和91.9%下降为40.5%和67.6%,对氨氮的去除率则分别由99.8%和99.9%下降为17.1%和22.2%,说明经高浓度氨氮驯化的污泥,其有机物降解菌和硝化菌都显示出对高浓度氨氮更好的适应性。     

兰炭废水中氨氮去除效果现场试验研究

采用氨氮吹脱—生物絮体吸附—混凝沉淀—改性兰炭吸附的组合工艺对兰炭废水中的氨氮去除效果进行了研究,并进行了现场试验。结果表明:在p H=11,温度35℃,气液比为6 000的条件下,氨氮的吹脱去除率为85%;投加活性污泥,控制废水MLSS为5 g/L,连续曝气12 h,控制聚合硫酸铁投加质量浓度为1.0~1.5 g/L,p H为6.5~7.5,氨氮去除率为80%;沉淀后出水用改性兰炭吸附,出水氨氮降至10~20 mg/L,氨氮去除率可达到99.5%。     

Synthesis of graphene oxide decorated with strontium oxide (SrO/GO) as an efficient nanocomposite for removal of hazardous ammonia from wastewater

ABSTRACT

In this research, graphene oxide decorated with strontium oxide (SrO/GO) is introduced as a new adsorbent material for the efficient removal of ammonia from industrial wastewater. The new adsorbent was thoroughly studied in terms of morphology, crystallography and chemical composition using characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and zeta potential analysis. Several parameters such as pH, adsorbent dosage, contact time, and ammonia initial concentration were investigated and optimized. Ammonia adsorption onto SrO/GO was validated with kinetics and adsorption isotherms by adopting different models. The results revealed that ammonia adsorption kinetic was of pseudo-second order (R² = 0.999) implying that chemisorption behavior and the equilibrium isotherm follows Langmuir model. This behavior shows a high maximum monolayer sorption capacity of 90.1 mg g^?1 at pH equal to 7 and contact time of 120 min pointing out the synergism advantageous effect. The abundant oxygen functional groups on the graphene oxide surface and the integrated Sr-O nanoparticles could efficiently interact with ammonia species creating a surface for more favorable and efficient removal of ammonia.     

臭氧催化氧化法对尾矿淋溶液中氨氮的去除研究

采用臭氧-载铜活性炭催化氧化法处理黄金尾矿闭库淋溶液,探讨了活性炭在臭氧氧化过程中的作用机理及p H对臭氧催化氧化降解氨氮的影响。试验结果表明:催化剂的投加显著提高了氨氮的去除率。初始p H为9.57时,O3氧化对氨氮的去除率仅为54.38%,而投加活性炭和载铜活性炭后,氨氮的去除率分别提高到63.92%和70.67%;随着废水的初始p H由7.2增加到11.43,氨氮的去除率由28.35%增加到99.45%。     

Metal‐free boron nitride adsorbent for ultra‐deep desulfurization

Activated metal‐free boron nitride (BN) adsorbent has been prepared by a surfactant assisted regulation strategy. By tuning the variety of surfactants (such as P123, PVP, F127), usage and reaction temperature, the adsorptive performance of activated BN was optimized. The optimized BN‐P123 adsorbent displays porous structure with a high surface area about 1185 m²/g and exhibits excellent adsorptive desulfurization activity for dibenzothiophene (45.7 mg S/g adsorbent for 500 ppmw sulfur model oil), which is comparable or even superior to the state‐of‐the‐art adsorbent. Additionally, this activated BN‐P123 could realize the ultra‐deep desulfurization through adsorptive process to reach the latest international standard (less than 10 ppmw). Considering the nontoxic metal‐free feature and the excellent adsorption performance, the obtained activated BN‐P123 may be a powerful candidate to meet the requirements of potential industrial applications. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3463–3469, 2017     

含金属氨络合离子的高浓度氨氮废水处理

对氨氮的质量浓度高达10 g/L以上的球镍废水采用空气吹脱技术进行处理,由于废水中氨氮浓度过高,且存在一定量的金属离子与氨形成金属氨络合离子,影响氨氮去除效果。采用延长吹脱时间和加入硫化钠破坏络合作用的方法,提高吹脱效率。试验证明,在反应进行至8～10 h后,加入适量硫化钠,可提高氨氮去除效果,并且对废水中的金属络合离子具有一定的去除作用。反应进行到34 h后,氨氮去除率达到99.1%;进行至46h后,氨氮去除率达到99.98%,氨氮的质量浓度由初始的12 870 mg/L降至3 mg/L。处理后的出水氨氮和铜离子分别达到《污水综合排放标准》(GB8978-1996)的一级和二级排放标准。