改性粉煤灰吸附处理含重金属离子废水的研究

实用技术
改性粉煤灰吸附处理含重金属离子废水的研究
彭荣华,陈丽娟,李晓湘
(湖南科技大学化学化工学院,湖南　湘潭　411201)
[摘　要]　以热电厂产生的粉煤灰为主要原料,通过加入一定量的硫铁矿烧渣和适量的固体Na 2Cl ,在90℃下用硫酸废液搅拌浸取2.5h ,再在300℃下焙制,得到一种吸附性能优良的吸附剂———改
性粉煤灰。

在静态条件下,研究了改性粉煤灰对重金属离子的吸附性能,着重探讨了改性粉煤灰去除工
业电镀废水中重金属离子Cr 6+,Pb 2+,Cu 2+,Cd 2+的适宜条件。

结果表明,p H 值是影响改性粉煤灰对重金属离子吸附的重要因素,各金属离子都有其适宜的p H 值范围。

在室温、p H =8.0时,各重金属离
子含量小于50mg/L 的含Cr (Ⅵ)电镀废水经改性粉煤灰吸附、沉淀处理后,各重金属离子的去除率达
97.5%以上,达到国家排放标准。

[关键词]　废水处理;吸附;改性粉煤灰;重金属离子[中图分类号]　X781.1　[文献标识码]　B [文章编号]　1001-1560(2005)01-0048-03
[收稿日期]　20040901
0　引　言
吸附法处理含重金属离子废水,通常采用活性炭作吸附剂[1]
,它具有吸附能力强、去除效率高等
优点,但价格较贵,其应用受到一定的限制。

粉煤灰是一种工业废渣,是从烧煤粉的锅炉烟气中收集的粉状灰粒,它细度较小且有着较高的比表面积[2],具有一定的吸附能力,在废水处理方面的研究和应用也有文献[3,4]报道。

在研究中发现,粉煤灰经适当改性后对溶液中的铬等重金属离子具有良好的吸附性能,进而对用改性粉煤灰分别处理含重金属离子铬、铅、铜、镉废水的适宜工艺条件进行了试验研究,并将它应用到电镀废水的处理,处理后的废水达到了排放标准。

可见,利用粉煤灰对工业废水进行处理可谓以废治废,且费用低廉,处理效果好。

1　试验部分
1.1　原料及其组成
粉煤灰取自湘潭电厂,其主要化学成分见表1。

硫铁矿烧渣取自湘潭钢铁公司,其中含Fe 2O 367.
58%;硫酸废液取自湘潭某电镀厂废液池,其主要化
学成分见表2。

重金属离子标准试液:分别配制质量浓度为5g/L 的Cr 6+,Pb 2+,Cu 2+,Cd 2+溶液作为储备液,用时稀释到所需浓度。

表1　粉煤灰的主要化学成分
成分SiO 2Al 2O 3Fe 2O 3MgO CaO C 质量分数/%
50.72
24.88
12.15
1.42
4.68
6.15
表2　硫酸废液的主要化学成分
成　分
H +Fe 2+Fe 3+物质的量浓度/(mol ・L -1)
4.67
0.02
0.35
注:使用前预先向废液加入氧化剂使Fe 2+氧化成Fe 3+。

1.2　改性粉煤灰的制备
将粉煤灰在105℃下烘干至恒重,并筛分至120目。

称取经上述处理过的粉煤灰2000g ,400g 硫铁矿烧渣和100g NaCl ,置于装有搅拌装置的1000mL 烧杯中,加入适量的并经氧化处理过的硫酸酸洗废
液,在90℃下缓慢搅拌(转速120r/min )2.5h ,然后在300℃左右温度下通风焙制,待其自然冷却至室温即得到试验所需的改性粉煤灰。

1.3　静态吸附试验
取一定量已知浓度的重金属离子溶液放入烧杯
8
4Jan.2005Vol.38No.1Materials Protection
中,加蒸馏水至1000mL,再加入一定量的改性粉煤灰(或未改性粉煤灰),用NaOH或HCl溶液调p H值至所需值,室温下搅拌40min,静置沉淀30 min,过滤,用原子吸收分光光度法(PE-4000AA)测定滤液中重金属离子的残留量,计算粉煤灰的吸附容量或重金属的去除率。

2　结果与讨论
2.1　粉煤灰与改性粉煤灰对Cr6+去除效果的比较
按粉煤灰(或改性粉煤灰)质量∶w(Cr6+)(以下简称“灰铬比”)=50∶
1加入粉煤灰(或改性粉煤灰),调pH值至8.0左右,搅拌40min,静置沉淀30min,其余步骤同基本试验方法,结果见表3。

表3　两种粉煤灰处理含C r6+废水的对比试验结果
ρ(Cr6+)/(mg・L-1)510152025
去除率/%
粉煤灰
改性粉煤灰
64.5
99.7
65.3
99.7
64.9
98.9
59.7
98.8
45.8
98.7
ρ(Cr6+)/(mg・L-1)3035404550
去除率/%
粉煤灰
改性粉煤灰
42.5
98.6
37.8
98.6
36.7
97.9
35.3
97.5
34.2
96.3
粉煤灰中含有较多的碳,这部分残碳本身就类似于活性炭,通过用酸在较高温度下浸提后,其表面和微孔内就变得更加粗糙,比表面积显著增加,即粉煤灰通过改性后其表面被活化,使其吸附性能得到进一步提高[5];另外,改性粉煤灰中的金属元素氧化物(Al2O3和Fe2O3)与硫酸反应,生成硫酸铝、硫酸铁盐,使粉煤灰在改性后又具有混凝性能。

因此,在处理含重金属离子的废水时,使用改性粉煤灰比只具有单一吸附性能的粉煤灰的处理效果好。

由表3可以看出,未改性的粉煤灰在各种质量浓度下对Cr6+的去除率都不超过70%,而经过改性的粉煤灰对Cr6+具有优良的吸附效果;同时,改性粉煤灰与未改性的粉煤灰对Cr6+的去除率随着溶液中Cr6+质量浓度增加而逐渐降低。

2.2　pH值对去除率的影响
固定溶液中Cr6+质量浓度为
40mg/L,搅拌40 min,沉淀30min,改性粉煤灰用量为Cr6+含量的50倍,试验结果见图1。

加入粉煤灰的主要作用是吸附和沉淀,吸附和沉淀的好坏对去除率的影响很大。

由图1可以看出,p H值在8.0～9.0的范围内效果较好,能使大部分铬离子被吸附,且Pb2+, Cu2+,Cd2+等重金属离子也部分被吸附,未被吸附的Pb2+,Cu2+,Cd2+等其他有害重金属离子则被沉淀。

同时,试验结果也显示,p H值过高不利于吸附,过低则不利于沉淀。

图
1　p H值对Cr6+去除率的影响
2.3　改性粉煤灰的用量对去除率的影响
固定溶液中Cr6+质量浓度为40mg/L,搅拌40 min,沉淀30min,在p H值为8.0的条件下,着重考察了改性粉煤灰用量对Cr6+去除率的影响,结果见图2。

由图2可以看出,灰铬比越大,Cr6+的去除率越高,但当灰铬比大于50以后,曲线变化趋于平稳。

同时试验结果也显示,在灰铬比大于50后,Pb2+, Cu2+和Cd2+的去除率也无明显的变化。

因此,试验时改性粉煤灰的用量按灰铬比为50进行投加。

图2　粉煤灰用量对Cr6+去除率的影响
2.4　吸附温度对去除率的影响
固定溶液中Cr6+质量浓度为40mg/L,搅拌40 min,沉淀30min,在p H值为8.0,灰铬比为50的条件下,考察了吸附温度对Cr6+去除率的影响,结果见图3。

用改性粉煤灰吸附处理含铬废水是一个既有物理作用又有化学作用的复杂过程,温度对这些过程均有不同程度的影响。

由图3可以看出,随着温度升高,Cr6+的去除率逐渐降低,这是因为吸附过程总是放热的,温度升高,不利于吸附的进行。

但在温度不超过30℃的条件下,Cr6+的去除率达到97.5%以上,且温度对去除率的影响不明显;只有当吸附温度超过30℃后,温度对Cr6+去除率的影响较为显著,且Cr6+的去除率下降较快。

因此,用改性粉煤灰吸附处理含铬等重金属离子废水时,可在
94
材料保护　2005年1月第38卷第1期
室温下进行吸附处理。

图3　吸附温度对Cr 6+去除率的影响
2.5　搅拌时间对去除率的影响
在其他试验条件相同的情况下,考察了搅拌时
间对Cr 6+去除率的影响。

结果表明,随着搅拌时间的延长,Cr 6+的去除率将逐渐升高,但在搅拌时间超过40min 以后,对Cr 6+去除率的影响不大。

因此,选择的搅拌时间为40min 。

2.6　改性粉煤灰处理不同重金属离子的试验
按照上述方法,室温下改性粉煤灰对各种重金属离子的吸附曲线见图4。

由图4可知,用改性粉煤灰分别吸附Cr 6+,Pb 2+,Cu 2+和Cd 2+,都有各自最佳的p H 值;当重金属离子浓度小于50mg/L 时,改性粉煤灰对Cr 6+,Pb 2+,Cu 2+,Cd 2+的吸附能力为Cr 6+>Cu 2+>Pb 2+>Cd 2+;改性粉煤灰对各种离子的吸附量与其浓度成正比,并随着重金属离子浓度的增大,吸附逐渐趋向饱和。

图4　改性粉煤灰对重金属离子的吸附曲线
Cr :p H =6.0　Cd :p H =7.0　Pb :p H =8.0　Cu :p H =9.0
2.7　改性粉煤灰处理电镀废水
取湘潭市某电镀厂的电镀废水500mL 放入烧
杯中,按灰铬比为50加入改性粉煤灰,用NaOH 和HCl 溶液调节水样p H 值为8.0左右,室温下搅拌40min ,静置沉淀30min 后,过滤,用原子吸收分光光度法分别测定滤液和原水样中各重金属离子的含
量,并计算各重金属离子去除率,结果见表4。

由表4可知,用改性粉煤灰处理电镀废水,处理效果较
好,各重金属离子的去除率较高,处理后的水样中各重金属离子的含量低于国家排放标准。

表4　改性粉煤灰对电镀废水的处理结果
金属离子
原液质量浓度/(mg ・L -1)
处理后质量浓度/
(mg ・L -1)
去除率/%
Cr 6+
35.400.4898.6Pb 2+28.400.6197.8Cu 2+23.600.4898.1Cd 2+
12.30
0.09
99.3
3　结　论
(1)改性粉煤灰较未改性粉煤灰去除废水中重
金属离子的效果要好,而且容易分离。

(2)p H 值对改性粉煤灰吸附处理含重金属离子的废水有较大影响,每一金属离子的去除都有一个自身适宜的p H ;在各自适宜的p H 值下,改性粉煤灰对重金属离子Cr 6+,Pb 2+,Cu 2+,Cd 2+的吸附能力为Cr 6+>Cu 2+>Pb 2+>Cd 2+。

(3)利用工业废渣———粉煤灰处理含重金属离子的废水具有以废治废、原料来源广泛易得、价格低廉等优点。

改性粉煤灰在重金属离子吸附饱和后可以不进行再生处理,同时原料来源丰富,工业操作简单,具有明显的经济效益和社会效益。

因此,改性粉煤灰在工业水处理中有着广阔的应用前景。

[
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本技术相关链接:
1.《电镀与环保》,2004,24(4):35.
2.《电镀与涂饰》,2004,23(6):36.
5Jan.2005Vol.38No.1Materials Protection
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K ey words:electroless nickel plating;zinc alloy die castings; NaH2PO2
ChromiumνFree P assivation T echnology at Low T emperature and F ast Speed for Copper and Its Alloy
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K ey words:clean production;low pollution;chromiumνfree passivating;copper and copper alloy;B TA
Structure and Properties of R are E arth Alloy Coating E lectrode2 posited in Aqueous Solution
WAN G Lingνling,TAN G Liνming,HUAN G Guiνfang,HUAN G Weiνqing,PEN G J un(Department of Ap2 plied Physics,Hunan University,Changsha410082,China). Cailiao B aohu2005,38(1),40～43(Ch).A review was given about the current state of the study on the structures and proper2 ties of rare earth alloy coatings electrodeposited from aqueous so2 lutions,and the perspectives for their development were pro2 posed.Thus the microstructure,amorphous phaseνforming rules,crystallization dynamics,magnetic performance,electro2 catalysis for hydrogen evolution,corrosion resistance,and me2 chanical and optical properties of the electrodeposited rare earth alloy coatings wear summarized.It was pointed out that the rare earth alloy films electrodeposited under specific conditions in aqueous solutions had amorphous structure and excellent magnet2 ic behavior,electrocatalytic activity for hydrogen evolution,cor2 rosion resistance,mechanical strength,and optical absorption properties.This accounted for the wide application of the elec2 trodeposited rare earth alloy coatings in nonνplane electron de2 vices with large coatings,magnetic bubble memory components, highνtemperature superνconductive films,magnetoνopti2 cal recording materials,electrode materials,luminescent materi2 als,laser materials,hydrogen storage materials,and surface en2 gineering and technology fields.
K ey words:aqueous solution electrodeposition;rare earth alloy; structure;properties Development of Study on R adiation Curing T echnology
WAN GJ uanνjuan1,MA Xiaoνyan1,CHAO Xiaoνlian2 (1.Department of Chemical Engineering,Northwestern Poly2 technical University,Xi’an710072;2.School of Chemistry and Material,Shanxi Normal University,Xi’an710062,China). Cailiao B aohu2005,38(1),44～47(Ch).With a view to the advantages including high efficiency,energy saving,pollution free,and excellent physical properties,and the fast growing worldwide,of radiation curing technology as a kind of green technologies,the development of radiation curing technology in recent years was reviewed.Thus a summarization was made on the dilute monomer and prepolymer,waterνbased ultraviolet νelectron beam(UV/EB)curing,cation photoνcuring,ra2 diationνcured powder coatings,composite curing system,UV νcured nano coatings,photoinitiator,and computer direct plate νmaking.At the same time,the market of radiation curing in China was investigated,and the development trend of the radia2 tion curing technology was forecasted.
K ey words:radiation curing;photoνcuring;UV/EB curing; ultraviolet
Adsorption of W astew ater Containing H eavy Metal Ions by Modif ied Fly Ash
PEN G Rongνhua,CHEN Liνjuan,L I Xiaoνxiang (School of Chemistry and Chemical Engineering,Hunan Univer2 sity of Science and Technology,Xiangtan411201,China). Cailiao B aohu2005,38(1),48～50(Ch).A modified fly ash absorbent with excellent adsorbability was prepared using the fly ash from a thermal power plant as the major raw materials.Thus the fly ash was mixed with a given amount of pyrite cinder and NaCl,stirred and immersed with waste sulfuric acid at90℃for 2.5h,and dried at300℃,to allow the generation of the target modified fly ash.The adsorption capability of the modified fly ash to various heavy metal ions was examined under static state condition,with an emphasis being placed on determining the suitable conditions for the removal of the heavy metal ions such as Cr6+,Pb2+,Cu2+,and Cd2+in industrial electroplating wastewater by the modified fly ash.The results showed that the adsorption capability of the modified fly ash to heavy metal ions was greatly dependent on the p H value of the wastewater to be treated,and the suitable p H value ranges varied for different metal ions.After absorbed by the modified fly ash at room tem2 perature and p H=8.0,the heavy metal ions in the Cr(V I)νcontaining electroplating wastewater with every individual heavy metal ion content below50mg/L was removed at a rate over97. 5%,and the treated wastewater passed the corresponding na2 tional discharge standard.
K ey words:wastewater treatment;adsorption;modified fly ash;heavy metal ion
Preparation of an E nvironmentally Acceptable W aterνB ased Anticorrosive Coating
HE Xinνkuai1,2,CHEN Baiνzhen1,2,CHEN Hong1, ZHOU Ningνbo1(1.School of Packaging and Printing, Zhuzhou Institute of Technology,Zhuzhou412008;2.Institute of Metallurgical Physical Chemistry and Material Chemistry, Central S outh University,Changsha410083,China).Cailiao B aohu2005,38(1),51～53(Ch).An environmentally accept2 able waterνbased anticorrosive coating was successfully devel2 oped in pursuing a universal antiνcorrosion coating applicable to the surfaces contaminated with rust,water,and oil,by re2 spectively preparing rust conversion solution and organic film forming solution.The formula and process of the titled coating were investigated,with an emphasis being placed on the effect of the coating components on its properties.It was found that the surfactant synthesized at our lab was able to strengthen the solu2 bility and dispersivity of the target coating,and the penetration accelerator acted to increase the adhesion between the coating and the substrate and the rigidity of the coating as well.The tar2 get coating was characterized by strong adhesion to the sub2 strate,fast speed for drying,excellent resistance to weathering,。