摘要
本文研究了高度风化的酸性红壤对Ｃｏ、Ｃｕ、Ｐｂ、Ｚｎ离子的吸附特性。用吸附曲线形状，吸附方程，分配系数，ｐＨ＿（５０）值等讨论了吸附亲和力特征及其影响因素和吸附反应的机理。结果表明，红壤粘粒吸附重金属离子主要由Ｆｅ、Ａｌ氧化物所控制。金属离子对红壤粘粒的吸附亲和力（以ｐＨ＿（５０）表示）主要决定于离子本身的化学性质，亲和力以Ｃｕ≥Ｐｂ＞ｚｎ＞Ｃｏ顺序减少，易水解的离子吸附亲和力较大，亲和力也受土壤组分及其表面性质影响，含Ｆｅ、Ａｌ氧化物多的粘粒其表面的反应活性也较大，对金属离子的亲和力较强。通过竞争吸附方程对吸附－ｐＨ曲线的描述和分配系数等的讨论，揭示出四种离子与红壤粘粒的反应机理并不相同，Ｃｕ、Ｐｂ离子以专性吸附反应为主，Ｚｎ、Ｃｏ则非专性吸附占一定比例。对专性吸附机理。
An experiment on the characteristics of Co,Cu,Pb and Zn adsorption
by sevenhighly weathered acid soils derived from different parent materials in different areasof
southern China was conducted to study affinity characteristics and factors affect-ing affinity as
well as the mechanism of adsorption reaction by using shapes of adsorpti-on curve,pH_(50)
values and competitive adsorption equations and distribution coeffici-ents.Clay fractions(<1μ
m)separated from red soils with different properties wereallowed to react with solutions of Co,
Cu, Pb and Zn in 25 ml 0.05 mol/L Ca(NO_3)_2as supporting electrolyte containing the desired
amount of adsorbate ion, respectively.The pH values of suspention were adjusted by adding
appropriate amounts of 0.1mol/LHNO_3 or saturated Ca(OH)_2 solution prior to metal addition
to obtain a criesof suspentions with various pn values. The results showed that the
adsorption-pH curves of metal ions by red soil clayshave very similar sigmoidal shapes which
differ mainly in displacement along thepH axis,suggesting that adsorption reactions of heavy
metal cations with the clayswere largely controiled by Fe or/and Al oxides, namely common
adsorption surfaces.Adsorption affinities(represented by pH_(50) values)of metal ions for all
red soil claysamples,which were mainly dependent upon the chemical properties of heavy
metalcations,decreased in the following order: Cu≥=pb>Zn>Co. The easily hydrolysedmetal
cations of relatively smaller p￣*K_1 have a higher affinity than those of largerP￣*K_1 . On
the other hand,adsorption affinity was also influenced by soil constituentsand their surface
properties.Surfaces of the clays dominated by Fe and Al oxidesstrongly adsorbed metal
cations because of much higher reactivity,so these claysshowed a greater affinity for metal
ions.Among properties of red soil,the principalfactors affecting adsorption affinity of heavy
metal cations on one adsorbent werethe content and form of Fe and Al oxides.etc.. Through fit
and description of competitive adsorption equation to the adsorpti-on-pH curves and discussion
of distribution coefficients,it was revealed that therewere a little differences in the mechanism
of reaction of the four metal cations wi-th red soil clays to some extent.Adsorption of Cu and Pb
cations appeared to bemainly controlled by specific adsorption mechanism,while Zn and Co
were thoughtto be adsorbed by mechanisms involving specific and non。specific
adsorption,suchas electrostatic adsorption。As to the specific adsorption mechanism,it was
reasona-ble to consider that there was a change from adsorption of the unhydrolysed metalion
and mono-hydroxo complex ion at low pH to the adsorption of the mono-hydro-xo complex at
higher pH.
出处
《土壤学报》
CAS
CSCD
北大核心
1995年第2期167-178,共12页
Acta Pedologica Sinica
基金
国家自然科学基金
关键词
酸性
红壤
重金属
吸附亲和力
吸附特性
Acid red soil,Heavy metal ions,Adsorption affinity.Adsorpti-on
Characteristics,Surface chemical properties
