Analysis of the location of physical adsorption state of ammonium in diffusion double layer on the surface of clay minerals

doi:10.16085/j.issn.1000-6613.2024-1499

Abstract

Abstract:

Ammonium in a physically adsorbed state, resulting from the ammonium salt leaching of ionic rare earth ores, is the primary source of environmental ammonia-nitrogen pollution. The location of its adsorption on the surfaces of clay minerals influences its desorption behavior. Formulas for calculating the thickness of the shear plane and the ion occupancy between the shear plane and the Gouy plane in a single electrolyte system were derived based on the Gouy-Chapman double-layer theory. Experimental measurements were obtained for the adsorption/desorption of physically adsorbed ammonium by Xinfeng (XF) and Xunwu (XW) ore samples, as well as the changes in zeta potential (ζ-potential) following adsorption/desorption. The findings indicated that ① the thickness of the shear plane and the Gouy plane was influenced by the electrolyte concentration of the system, and as the electrolyte concentration increased, both the shear plane and the Gouy plane moved towards the surface of the clay particles, becoming thinner; ② at saturation adsorption of physical adsorption of ammonium, the experimental adsorption amount of XF tailings accounted for 98% of the theoretical storage between the Gouy plane and the shear plane, while XW tailings accounted for 96%. The first desorption amount of physically adsorbed ammonium in XF tailings reached 75%, and that in XW tailings reached 90%, suggesting that physically adsorbed ammonium was primarily located between the Gouy plane and the shear plane with a significant presence near the Gouy plane; and ③ as the desorption of physically adsorbed ammonium in tailings proceeds, the ζ-potential within the diffusion layer decreased. Intermittent leaching can increased the ζ-potential, promoting the desorption of physically adsorbed ammonium and offering a potential solution for the management of ammonia-nitrogen pollution in ionic rare earth mines.

Key words: ionic rare earth ores, double layer, physical adsorption state, adsorption, desorption, diffusion

摘要：

物理吸附态铵是离子型稀土矿铵盐浸矿后造成环境氨氮污染的主要来源，在黏土矿物表面的赋存位置影响其解吸行为。本文根据Gouy-Chapman双电层理论推导得到单一电解质体系中滑动面厚度、滑动面与Gouy面之间离子赋存量的计算公式，实验测得信丰（XF）和寻乌（XW）矿样吸附/解吸物理吸附态铵的量以及吸附/解吸后zeta电势（ζ电势）的变化。结果表明：①滑动面和Gouy面厚度受体系电解质浓度影响，电解质浓度增加，滑动面和Gouy面向黏土颗粒表面移动，厚度变薄；②物理吸附态铵饱和吸附时，XF尾矿实验吸附量占Gouy面与滑动面之间理论赋存量的98%，XW尾矿占96%，XF尾矿物理吸附态铵的一次解吸量达75%，XW尾矿达90%，表明物理吸附态铵在扩散层内的赋存位置为Gouy面和滑动面之间，且主要赋存在Gouy面附近；③随着尾矿物理吸附态铵的解吸，扩散层内ζ电势降低，通过间歇淋洗，能增大ζ电势，促进物理吸附态铵的解吸，为离子型稀土矿山氨氮污染治理提供了解决思路。

关键词: 离子型稀土矿, 双电层, 物理吸附态, 吸附, 解吸, 扩散

CLC Number:

TD983

LIN Fuming, WANG Guanshi, QIN Lei, PENG Chenliang. Analysis of the location of physical adsorption state of ammonium in diffusion double layer on the surface of clay minerals[J]. Chemical Industry and Engineering Progress, 2025, 44(10): 6093-6101.

林福明, 王观石, 秦磊, 彭陈亮. 黏土矿物表面扩散双电层中物理吸附态铵赋存位置分析[J]. 化工进展, 2025, 44(10): 6093-6101.

Figures/Tables 11

References 29

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矿样	初始铵浓度/mg·L^-1	Gouy面厚度/nm	滑动面厚度/nm	厚度差/nm
XF	8	5.36	4.48	0.88
XF	9	4.98	3.94	1.04
XW	5	5.28	2.78	2.50
XW	6	4.71	2.06	2.65

矿样	初始铵浓度/mg·L^-1	Gouy面厚度/nm	滑动面厚度/nm	厚度差/nm
XF	8	5.36	4.48	0.88
XF	9	4.98	3.94	1.04
XW	5	5.28	2.78	2.50
XW	6	4.71	2.06	2.65

矿样	初始铵浓度/mg·L^-1	滑动面厚度/nm	理论赋存量/mg·g^-1	实验吸附量/mg·g^-1
XF	20	0.69	0.10	0.06
	40	0.48	0.14	0.10
	60	0.39	0.16	0.13
	200	0.21	0.30	0.28
	400	0.15	0.42	0.40
	600	0.12	0.49	0.48
XW	20	0.12	0.07	0.02
	40	0.07	0.10	0.05
	60	0.06	0.12	0.07
	200	0.05	0.21	0.19
	400	0.05	0.22	0.20
	600	0.04	0.27	0.26

矿样	初始铵浓度/mg·L^-1	滑动面厚度/nm	理论赋存量/mg·g^-1	实验吸附量/mg·g^-1
XF	20	0.69	0.10	0.06
	40	0.48	0.14	0.10
	60	0.39	0.16	0.13
	200	0.21	0.30	0.28
	400	0.15	0.42	0.40
	600	0.12	0.49	0.48
XW	20	0.12	0.07	0.02
	40	0.07	0.10	0.05
	60	0.06	0.12	0.07
	200	0.05	0.21	0.19
	400	0.05	0.22	0.20
	600	0.04	0.27	0.26