碳化温度对稻壳生物炭的影响及其对Cr(Ⅵ)的吸附性能

以稻壳为原料,在不同的温度(300,500和700℃)下采用限氧碳化法制备了生物炭,并利用扫描电镜(SEM)和红外光谱(FTIR)表征了生物炭的结构和性质,同时考察了pH值对生物炭吸附的影响,初步探讨了吸附机理。结果表明,制备的生物炭官能团种类和总量相近,均含有烷基、芳香基及一些含氧官能团,随着碳化温度的升高芳香族化合物增加,芳香化程度增强。试验条件下稻壳生物炭(RH700)对Cr(Ⅵ)的饱和吸附量达到16.68 mg/g,降低pH值有利于对Cr(Ⅵ)的吸附。稻壳生物炭等温吸附曲线更符合Langmuir模型,对吸附过程中焓(△H)、熵(△S)和吉布斯自由能(△G)的计算表明,稻壳生物炭对Cr(Ⅵ)的吸附是自发的吸热反应,其吸附行为更符合伪二级动力学模型,拟合的qe值与实测值相差小于0.38 mg/g。颗粒内扩散表明膜扩散和颗粒内扩散共同控制着吸附过程。     

The effects of alkalinity and acidity of process water and hydrochar washing on the adsorption of atrazine on hydrothermally produced hydrochar

Hydrothermal carbonization of simulated food waste was performed at 250 °C for 20 h using deionized water (DI) and 0.01 N solutions of HCl, NaCl, and NaOH. The hydrochars produced were washed with acetone and the adsorptive capacity of the washed and unwashed hydrochars for atrazine were characterized. Using a generalized linear model, it was shown that the adsorptive capacity of the washed hydrochar was significantly higher than that of the unwashed hydrochars. The HCl processed unwashed hydrochar has a slightly higher adsorptive capacity compared to the DI processed hydrochar while both the NaOH processed washed and unwashed hydrochars were slightly lower than the corresponding DI processed hydrochars. ¹³C solid-state NMR results showed no discernible differences in surface functional groups among the washed hydrochars and among the unwashed hydrochars. A clear decrease in alkyl groups and an increase in aromatic/olefinic-C groups were observed after acetone washing. ¹H liquid-phase NMR showed carbon alkyl chains were present in the acetone wash. Interaction energies calculated using dispersion corrected density functional theory show that atrazine is more strongly adsorbed to surfaces without weakly associated alkyl groups.     

Resembling a “natural formation pattern” of chlorinated dibenzo-p-dioxins by varying the experimental conditions of hydrothermal carbonization

Until several years ago dioxins were considered as just an unwanted by product of anthropogenic activities and stigmatized as the symbol of man-made environmental pollution. Natural processes, such as forest fires, can emit dioxins, but compared to industrial processes, usually very low quantities are emitted. However after a case of food contamination occurred in the United States of America in 1996 caused by kaolinitic clay a discussion on the provenience started. Besides the relatively high concentration also an unusual PCDD/F distribution pattern was found in these ball clay samples. This specific pattern related to none of the known anthropogenic sources for these contaminants and, in relation to a supposed natural formation, later it was named “natural formation pattern”. Hydrothermal carbonization (HTC) can transform biomass within hours into a brown coal-like product which resembles naturally occurring coal formation. HTC can also transform an already present PCDD/F contamination in a way to obtain a “natural formation pattern” characterized by an unusual high ratio between 1,2,3,7,8,9-HxCDD and 1,2,3,6,7,8-HxCDD and the absence of almost all chlorinated dibenzofurans. By varying the experimental conditions of the HTC process applied to sewage sludge samples contaminated with PCDD/Fs from anthropogenic sources, beside the “natural formation pattern” at a temperatures of 255 °C, a remarkable increase of the toxicity based on WHO–TEQ was observed.     

不同Cu交换分子筛脱除柴油机尾气中的NOx

以BEA、ZSM-5和SAPO-34分子筛为载体,采用离子交换法制备了用于柴油机尾气中氨选择性催化还原(NH3-SCR)NOx的Cu改性分子筛催化剂.采用XRF、ICP、H2-TPR、和NH3-TPD等表征对催化剂样品的理化特性进行了分析.结果表明,分子筛类型影响铜交换量和铜物种的存在状态.借助H2-TPR和UV-Vis分析可以清晰地看出,在不同类型的分子筛上Cu的还原能力和配位环境明显不同.铜元素引入后,3类分子筛的SCR活性都有明显的改善.3种Cu-交换分子筛的抗高温水热老化能力却明显不同:老化的Cu-SAPO-34依然保持良好脱硝性能而老化的Cu-ZSM-5严重失活.     

溴掺杂TiO_2光催化剂的制备与性能研究

以KBr和Ti(SO4)2为原料,通过水热法制备了高催化活性的溴掺杂纳米TiO2(Br-TiO2)光催化剂,利用XRD、XPS、TEM、BET和UV-Vis DRS等测试手段对其进行了表征。通过苯酚降解实验评价了Br-TiO2的光催化活性。结果表明,700℃焙烧、溴与钛的摩尔比为0.35∶1时,Br-TiO2具有最佳光催化活性。该催化剂为晶体发育完整的锐钛矿相TiO2,粒径平均大小为50 nm,比表面积为16.81 m2/g,在紫外区的吸收得到加强,光催化能力优于Degussa P-25。确定了降解苯酚的最佳条件:催化剂投加量为0.5 g/L,苯酚初始浓度为10 mg/L,pH值为6.0。     

H3PO4活化制备喜旱莲子草基活性炭及性能表征

为了解决喜旱莲子草入侵带来的环境污染和生态破坏问题,探索了综合利用其制备价廉、质优活性炭的可能性、在正交实验的基础上,对实验结果进行了单因素方差分析,结果表明,控制因素对活性炭得率和碘吸附值的影响大小均依次为:炭化温度＞炭化时间＞浸渍时间＞浸渍比,且前三者有显著影响、极差分析表明最佳制备工艺组合为:浸溃比4∶1、浸渍时间6h、炭化温度873 K和炭化时间1h.在最佳制备条件下制得的喜旱莲子草基活性炭得率和碘吸附值为:37.44％和752.36 mg/g;其比表面积、总孔体积、平均孔径和中孔率分别为:1 100.720 m2/g、0.610 cm3/g、2.216 nm、72.00％.红外光谱分析表明,活性炭形成了大量表面官能团,主要有以下几种:羧基、酚基、醚基等、正交实试和物理特性表征均表明,喜旱莲子草是良好的中孔活性炭制备原料.     

氧化镍纳米片光催化降解蒽醌染料B-RN的研究

采用水热法制备NiO纳米薄片,用XRD和TEM对样品的晶型及颗粒形貌进行了表征。以蒽醌染料B-RN为对象,紫外灯为光源,研究了催化剂热处理温度、催化剂用量、光照时间、染料的初始浓度等因素对染料脱色率的影响,以及催化剂的重复利用。结果表明:NiO薄片催化剂能显著的降解蒽醌染料B-RN,且能重复利用。     

水热改性棉铃壳对水中氟的吸附

采用水热法制备了改性棉铃壳吸附剂,通过比表面积分析仪、扫描电镜和红外光谱仪表征了棉铃壳改性前后表面结构和官能团变化,并通过批实验分析了改性棉铃壳对水中F-吸附动力学及热力学特征,考察了温度、pH对吸附性能的影响。结果表明,磷酸水热改性后棉铃壳比表面积为121.7 m2/g,是改性前的18.5倍;通过水热改性可以减少酸性基团数量,有利于吸附阴离子。氟离子吸附实验结果显示,吸附反应符合准二级动力学模型,Langmuir模型能更好地描述反应的单分子层吸附特征,分离因子R L在0~0.5之间。改性棉铃壳对F-的吸附属于自发进行的吸热反应。     

Eu掺杂ZnO光催化剂降解制药废水

以醋酸锌(Zn(CH3COO)2)和六水合硝酸铕(Eu(NO3)3·6H2O)为主要原料,氢氧化钠(Na OH)为沉淀剂,聚乙二醇(PEG2000)为矿化剂,柠檬酸为p H调节剂,采用水热法制备Eu掺杂Zn O复合纳米棒光催化材料粉体。用制备的粉体对制药废水进行光催化降解实验,并研究了反应温度、反应时间、光照条件和掺杂比对其光催化氧化效果的影响。用XRD、TEM和EDS等测试手段对粉体进行了表征。研究结果表明,水热反应温度为160℃,时间为6 h,制备的3%Eu掺杂Zn O复合纳米棒光催化材料的光催化效果较好,在365 nm的紫外灯照射下150 min后,制药废水的脱色率达38.8%,COD的降解率达57.5%。     

联碱厂碳化塔洗水制备磷酸铵镁

采用化学沉淀法,以模拟联碱厂碳化塔洗水为原料,制备磷酸铵镁,并采用SEM和XRD技术对产品的晶形和成分进行分析。通过正交实验和单因素优化实验确定较适宜的反应条件为：反应液pH 9.5,n（Mg）∶n（P）∶n（N）=1.2∶1.1∶1.0,反应温度25 ℃。在此条件下,处理氨氮质量浓度为7 500 mg/L的联碱厂碳化塔洗水,氨氮的利用率为97.4%,制备的磷酸铵镁产物晶形比较规则,呈斜立方正交结构。1 t氨氮质量浓度为7 500 mg/L的联碱厂碳化塔洗水可生产磷酸铵镁0.139 2 t,产品收益约为320.2 元,药剂成本为352.3 元,即废水的处理费用约为32.1 元/t。