活性氧化铝吸附除氟性能研究

活性氧化铝作为常用的除氟吸附剂,有专一的除氟性。选用粒径为2~4mm的活性氧化铝,通过静态吸附试验和动态连续流滤柱试验,探究了其吸附除氟性能的影响因素。结果表明:活性氧化铝除氟最佳pH值为5,吸附平衡时间为5h,SO_4^(2-)对活性氧化铝的静态吸附影响较大;增大滤速或降低滤料填充高度会使除氟效率降低,超标时间和滤柱穿透时间缩短。

铝改性赤泥吸附剂的制备及其除氟效能的研究

以铝工业废矿渣为原材料，通过铝盐改性及焙烧活化处理，制备了水中除氟吸附剂。研究考察了吸附剂吸附氟能力、反应时间、pH值以及投加量对吸附效果的影响。结果表明，铝改性赤泥吸附剂具有较好的除氟效果，未焙烧铝改性赤泥吸附剂及经过200℃焙烧活化赤泥吸附剂的饱和吸附量分别达到68．07和91．28mg·g^-1，远高于原状赤泥的饱和吸附量13．46mg·g^-1。经吸附后出水氟含量低于1mg·L^-1的国家饮用水标准。吸附规律符合Langmuir等温方程，溶液pH值显著影响除氟效果，在溶液pH值为7—8时达到最佳去除效果。

一步固相反应制备铝改性活性炭对矿井水中氟化物的超快去除

矿井水中(F^(−))超标已成为制约我国西部矿区煤炭绿色开发的主要挑战之一。针对该问题,开发了机械化学法一步固相反应制备Al改性活性炭(AC-Al)的方法,解决了常规水热法改性活性炭产生废液废渣、制备周期长的问题,并实现了矿井水中F^(−)的快速、高效去除。研究了Al添加量、pH、共存阴离子和有机物、吸附剂投加量及反应时间等对除氟性能的影响。AC-Al除氟性能与Al添加量成正比,添加量为0.32 g,吸附反应30 s时,水中F^(−)去除率达到80%以上。pH在3~10范围内,F^(−)去除率均大于80%,具有良好的水质适应性。吸附过程更符合Langmuir模型,即为单层吸附,理论饱和吸附量为1.47 mg/g。吸附过程符合准一级动力学模型。硫酸根离子、氯离子和碳酸氢根离子(1000 mg/L时)、腐殖酸对F^(−)去除没有影响,氯离子和碳酸氢根离子质量浓度为3000 mg/L时,除氟率分别降低约21%和11%。AC-Al投加量为10 g/L时,矿井水中F^(−)去除率达84.9%(30 s内),质量浓度从4.85 mg/L降低至0.73 mg/L,满足《地表水环境质量标准》(GB3838—2002)中F^(−)浓度限值(I、II、III类),矿井水中F^(−)吸附过程同样符合准一级动力学模型。元素面分布表明,Al均匀地负载于活性炭表面;F^(−)均匀吸附在AC-Al上,与Al分布特征相似,证明Al是F^(−)吸附潜在活性位点。X射线光电子能谱结果表明,F^(−)吸附前后,AC-Al表面的Al元素结合能从74.20 eV升高至74.28、77.80 eV等2种状态,说明Al与F结合形成了Al-FOH、Al-F化学键,是快速稳定除氟的直接原因。同时,AC-Al吸附剂上的Al溶出量很低(0.34μg/g)。机械化学法制备的Al改性活性炭除氟效果良好,可为除氟吸附剂制备提供新的普适性技术路径,同时为解决矿井水除氟问题提供技术支撑。

化学沉淀法处理除氟吸附剂再生尾液的试验研究

通过试验研究了投加石灰法、投加氯化钙法、石灰-氯化钙联合法、石灰-盐酸联合法4种化学沉淀法对除氟吸附剂再生尾液的处理效果和影响因素。结果表明:静置沉淀90min后,使用投加石灰法处理pH值为12、含氟浓度为2 000mg/L的除氟吸附剂再生尾液,处理后残余氟离子浓度大于50mg/L,使用投加氯化钙法,处理后残余氟离子浓度小于20mg/L,使用石灰-氯化钙联合法和石灰-盐酸联合法,处理后残余氟离子浓度均小于10mg/L;4种方法的最佳搅拌强度为150r/min,最佳反应pH值为12左右,最佳静置时间为90min;其中,采用石灰-盐酸联合法处理pH值为12、含氟浓度为2 000mg/L的高氟再生尾液,在石灰投加量超过理论量60%(即为6.231 6g/L),加入65.4mL/L 2M的HCl时,出水可以达到国家污水排放一级标准,且pH值在7左右。

含氟废水安全保障技术研究

许多行业产生的废水中都含有大量氟离子,电子元件生产、电镀和金属冶炼等行业排放的废水中都含有高浓度氟化物。而目前缺乏经济性好且适用性强的除氟方法,针对氟化物去除难度大、达标困难这一典型问题,采用不同的制备方法,制备了羟基氧化铁和两种铈基吸附剂,研究了吸附等温模型、吸附动力学以及pH对吸附的影响。结果表明:3种吸附剂在吸附过程中化学吸附起主要作用,整个吸附过程符合准二级反应动力学模型。与另外两种吸附剂相比铈吸附剂B去除效果更好,且pH在2~10范围内,氟离子去除率稳定在80%以上。

Preparation of 2D carbon ribbon/Al_(2)O_(3) and nitrogen-doped carbon ribbon/Al_(2)O_(3) by using MOFs as precursors for removing high-fluoride water

2D carbon ribbon/Al_(2)O_(3) was synthesized with two-dimensional metal organic frameworks 2D-MOFs as precursors using the solvothermal and calcination methods.Batch experiments of adsorption parameters such as pH,liquid/solid ratio,adsorption kinetics,adsorption thermodynamics,and anions competitions were investigated to understand the adsorptive behavior of fluoride on carbon ribbon/Al_(2)O_(3) and nitrogen-doped carbon ribbon/Al_(2)O_(3).The adsorption of fluoride on carbon ribbon/Al_(2)O_(3) could be described as the chemical and multilayer adsorption,while the adsorption of fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) followed the chemical and monolayer adsorption phenomenon.The fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) had a much faster adsorption rate of 3.1×10^(−7) m/s than carbon ribbon/Al_(2)O_(3),which was 1.2×10^(−7) m/s.The nitrogen-doping on carbon ribbon enhances structural defects and improves the adsorption performance of fluoride.Also,the diacetylene linkages(—C≡C—)and pyridinic-N were studied to understand their influences on removing fluoride.The result indicates that carbon ribbon and nitrogen-doped ribbon could serve as good adsorbents for removing fluoride.

Fluoride Removal by Lanthanum Alginate Bead: Adsorbent Characterization and Adsorption Mechanism

Lanthanum alginate bead is a new, highly active adsorbent. In the present study, we investigated its ad- sorption performance and its adsorption mechanism. The adsorption isotherm for fluoride onto lanthanum alginate b ead fits the Langmuir model well, and the maximum adsorption capacity is 197.2 mg·g-1. X-ray diffraction shows the amorphous nature of lanthanum alginate bead, which allows for better accessibility to fluoride and thus better activity. Infrared spectra of lanthanum alginate bead before and after adsorption confirm its stable skeletal structure. Scanning electron microscopy shows that the dense surface structure of the adsorbent appear cracks after adsorption. T he adsorption mechanism of lanthanum alginate bead is considered as an ion exchange between F- and Cl- or OH-, as verified from the adsorbent and the solution by pH effect, energy dispersive X-ray, and ion chromatography.

Development of a novel nano-biosorbent for the removal of fluoride from water

The study was designed to investigate the use of two sorbents namely(i) Fe3O4 nanoparticles immobilized in sodium alginate matrix(FNPSA) and(ii) Fe3O4 nanoparticles and saponified orange peel residue immobilized in sodium alginate matrix(FNPSOPR) as sorbents for fluoride removal from contaminated water. The synthesized nanoparticles were analyzed and characterized by dynamic light scattering, X-ray diffraction, vibrating sample magnetometry, and scanning electron microscopy with energy dispersive X-ray spectroscopy and Fourier transform-infrared spectrometry. The sorbent matrices were prepared in the form of beads and surface functionalized to enable enhanced sorption of fluoride ions. Batch sorption studies were carried out and the sorption isotherm and reaction kinetics were analyzed. Both the sorbents followed Langmuir model of isotherm and fitted well with Pseudo first order reaction. The maximum sorption capacity exhibited by FNPSA and FNPSOPR was58.24 mg·g-1and 80.33 mg·g-1respectively. Five sorption–desorption cycles exhibited 100%, 97.56%, 94.53%,83.21%, and 76.53% of regeneration of FNPSOPR. Accordingly, it is demonstrated that FNSOPR could be used as a promising sorbent for easy and efficient removal of fluoride from contaminated water with good reusability.The current work suggests a simple and effective method to remove fluoride from contaminated water.