Effect of organic flocculant on settling performance of iron-bearing minerals and its adsorption mechanism

doi:10.11949/0438-1157.20220405

Abstract

Abstract:

The effect of ammonium polyacrylate (PAAA), anionic polyacrylamide (APAM) and hydroxamic acid flocculant (HPAM/HCPAM) on the settling performance of hematite and goethite by simulating the Bayer red mud settlement was studied, and the particle size distribution and fractal dimension of flocs as well as the flocculation mechanism were analyzed by Fourier transform infrared spectroscopy. Among the different types of flocculants, the iron ore phase sedimentation rate is the fastest with the addition of hydroxamic acid flocculant, and the higher the hydroxamic acid content, the better the sedimentation performance; the ammonium polyacrylate and anionic polyacrylamide flocculants have little effect on the settling performance of iron-bearing minerals; under the same conditions, the settling velocity of hematite is much higher than that of goethite, and increasing the amount of flocculant helps to improve the settling velocity of goethite. Among the hematite flocs, the PAAA flocs have the largest particle size, while the HPAM flocs have the largest fractal dimension and the best compactness; among the goethite flocs, the APAM flocs have the largest particle size, while the HCPAM flocs have the largest fractal dimension and the best compactness. The hydroxamic acid flocculant forms a five membered ring chelate with a stable structure and strong adsorption capacity with hematite and goethite, which enhances the flocculation performance of hematite and goethite; PAAA is adsorbed with hematite through bidentate bridging, and adsorbed with goethite through monodentate coordination, the adsorption capacity of which is weaker than five-membered ring; APAM adopts the chemical adsorption with hematite and goethite with a poor settling performance.

Key words: sedimentation, adsorption, flocculation, particle size distribution, hematite, goethite

摘要：

通过模拟拜耳法赤泥沉降过程研究了聚丙烯酸铵(PAAA)、阴离子聚丙烯酰胺(APAM)和氧肟酸絮凝剂(HPAM/HCPAM)对赤铁矿和针铁矿沉降性能的影响规律和絮凝后絮体的粒径分布及分形维数，并利用傅里叶变换红外光谱探讨了絮凝剂与铁矿相的吸附机理。在不同类型絮凝剂中，添加氧肟酸絮凝剂铁矿相沉降速度最快，且氧肟酸含量越高，沉降性能越好；聚丙烯酸铵和阴离子聚丙烯酰胺絮凝剂对铁矿相沉降性能影响较小；同等条件下赤铁矿沉降速度要远高于针铁矿，增加絮凝剂添加量有助于提高针铁矿沉降速度。在赤铁矿絮体中，添加PAAA絮体粒径最大，HPAM絮体分形维数最大、致密性最好；在针铁矿絮体中，添加APAM絮体粒径最大，HCPAM絮体分形维数最大、致密性最好。氧肟酸絮凝剂与铁矿相形成结构稳定、吸附能力强的五元环状螯合物，增强了赤铁矿和针铁矿的絮凝效果；PAAA通过双齿桥接配位与赤铁矿表面发生吸附，通过单齿配位与针铁矿表面发生吸附，其吸附能力弱于五元环；APAM与赤铁矿和针铁矿表面发生化学吸附，沉降性能差。

关键词: 沉降, 吸附, 絮凝, 粒度分布, 赤铁矿, 针铁矿

CLC Number:

TF 803.23

Tongpeng LU, Xiaolin PAN, Hongfei WU, Yu LI, Haiyan YU. Effect of organic flocculant on settling performance of iron-bearing minerals and its adsorption mechanism[J]. CIESC Journal, 2022, 73(9): 4122-4132.

鲁统鹏, 潘晓林, 吴鸿飞, 李煜, 于海燕. 有机絮凝剂对铁矿相沉降性能影响及其吸附机理[J]. 化工学报, 2022, 73(9): 4122-4132.

Figures/Tables 13

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Flocculant type	Functional group
ammonium polyacrylate (PAAA)	—COO^-
anionic polyacrylamide (APAM)	—CONH₂，—COO^-
mixed hydroxamic acid (HPAM)	—CONHOH，—CONH₂，—COO^-
high content hydroxamic acid (HCPAM)	—CONHOH

Flocculant type	Functional group
ammonium polyacrylate (PAAA)	—COO^-
anionic polyacrylamide (APAM)	—CONH₂，—COO^-
mixed hydroxamic acid (HPAM)	—CONHOH，—CONH₂，—COO^-
high content hydroxamic acid (HCPAM)	—CONHOH

Iron-bearing mineral	Flocculant	v₁/(m·h^-1)	v₅/(m·h^-1)	Compression ratio/%	Supernatant turbidity/NTU
hematite	no flocculant	0.621	0.738	24.88	70.71
	PAAA	0.771	0.842	25.71	136.59
	APAM	0.481	0.718	26.83	114.53
	HPAM	4.434	1.716	21.46	327.76
	HCPAM	7.397	1.759	19.51	292.47
goethite	no flocculant	0.046	0.029	89.50	221.00
	PAAA	0.068	0.041	88.00	160.71
	APAM	0.025	0.026	92.00	88.94
	HPAM	0.246	0.211	62.50	32.47
	HCPAM	0.305	0.508	53.00	30.41

Iron-bearing mineral	Flocculant	v₁/(m·h^-1)	v₅/(m·h^-1)	Compression ratio/%	Supernatant turbidity/NTU
hematite	no flocculant	0.621	0.738	24.88	70.71
	PAAA	0.771	0.842	25.71	136.59
	APAM	0.481	0.718	26.83	114.53
	HPAM	4.434	1.716	21.46	327.76
	HCPAM	7.397	1.759	19.51	292.47
goethite	no flocculant	0.046	0.029	89.50	221.00
	PAAA	0.068	0.041	88.00	160.71
	APAM	0.025	0.026	92.00	88.94
	HPAM	0.246	0.211	62.50	32.47
	HCPAM	0.305	0.508	53.00	30.41

Iron-bearing mineral	Flocculant	D_(0.1)/μm	D_(0.5)/μm	D_(0.9)/μm	Specific surface area/(m²‧kg^-1)
hematite	no flocculant	0.06	3.91	11.80	32390
	PAAA	14.33	63.07	186.33	182.13
	APAM	11.40	42.38	186.00	223.73
	HPAM	13.00	36.63	80.87	236.47
	HCPAM	15.40	59.40	135.33	181.17
goethite	no flocculant	0.11	6.25	29.73	12230
	PAAA	13.10	43.60	125.00	83.27
	APAM	14.60	46.10	99.50	80.23
	HPAM	10.80	26.40	71.50	132.90
	HCPAM	12.40	33.50	106.00	87.70