Synthesis of nickel pigments using waste foundry sand as a silica source

Martin, A. C.; Schabbach, L. M.; Folgueras, M. V.

doi:10.1590/0366-69132019653762756

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Articles • Cerâmica 65 (376) • Oct-Dec 2019 • https://doi.org/10.1590/0366-69132019653762756 copy

Synthesis of nickel pigments using waste foundry sand as a silica source

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Pigments of Zn_2-xNi_xSiO₄ system were synthesized varying molar ratio of zinc and nickel, starting from willemite (Zn₂SiO₄) to olivine (Ni₂SiO₄) structure, using waste foundry sand (WFS) and commercial silica as sources of SiO₂. WFS was characterized by chemical analysis and XRD. The synthesis of pigments was performed by ceramic route with x = 0, 0.5, 1, 1.5 and 2.0 mol and calcination at 1200 ºC. They were characterized by XRD and colorimetric measurements. Results showed that, despite the presence of alumina and iron traces in the WFS composition, the crystalline phases of pigments and their colors were similar for both silica sources. Also, lower additions of nickel favored the willemite formation, while higher ones favored the olivine formation. The brown color was noticed when the pigments were dispersed in two types of ceramic glazes and fired in a semi-industrial oven; as a result, instability was identified. However, the feasibility of obtaining pigments by replacing commercial silica with WFS was confirmed.

Keywords:
solid residues; ceramic pigments; chromatic stability

Tabela I Nomenclatura utilizada para identificar os pigmentos obtidos.

X	Composto de interesse	Sílica comercial	Resíduo
0	Zn₂SiO₄	Z₂S	Z₂R
0,5	Zn_1,5Ni_0,5SiO₄	N_0,5S	N_0,5R
1,0	Zn₁Ni₁SiO₄	N₁S	N₁R
1,5	Zn_0,5Ni_1,5SiO₄	N_1,5S	N_1,5R
2,0	Ni₂SiO₄	N₂S	N₂R

Tabela II Composição química (% em massa) da areia descartada de fundição.

	SiO₂	Al₂O₃	Fe₂O₃	SO₃	K₂O	CaO	TiO₂	Outros	PF	Total
ADF1	85,95	9,35	1,11	1,38	0,79	0,43	0,38	0,31	0,30	100,00
ADF2	85,05	9,70	1,11	1,25	0,78	0,42	0,38	1,02	0,30	100,00
ADF3	85,90	9,59	1,16	1,15	0,79	0,43	0,38	0,30	0,30	100,00
Média	85,63	9,55	1,13	1,26	0,78	0,43	0,38	0,54	0,30	100,00

Tabela III Parâmetros L*a*b* dos pigmentos na forma de pó.

Amostra	L*	a*	b*	ΔL	Δa	Δb
Z₂S	26,33	0,20	-0,73	15,47	-0,32	0,26
Z₂R	41,80	-0,12	-0,47	15,47	-0,32	0,26
N_0,5S	68,94	-14,63	-5,32	11,52	5,12	29,22
N_0,5R	80,46	-9,51	23,90	11,52	5,12	29,22
N₁S	79,31	-16,55	16,57	-7,22	6,44	0,29
N₁R	72,09	-10,11	16,86	-7,22	6,44	0,29
N_1,5S	74,15	-12,14	28,98	4,28	6,10	1,94
N_1,5R	78,43	-6,038	30,92	4,28	6,10	1,94
N₂S	89,79	-17,15	24,08	-9,33	7,64	-0,18
N₂R	80,46	-9,511	23,90	-9,33	7,64	-0,18

Tabela IV Parâmetros L*a*b* para esmalte mate/opaco com 3 wt% dos pigmentos sintetizados.

Amostra	L*	a*	b*	>ΔL	>Δa	>Δb	>ΔE
Z₂S	91,03	-0,68	7,18	0,45	0,02	0,18	0,49
Z₂R	91,48	-0,66	7,36	0,45	0,02	0,18	0,49
N_0,5S	71,78	3,20	15,26	0,50	-0,16	-0,17	0,55
N_0,5R	72,28	3,04	15,09	0,50	-0,16	-0,17	0,55
N₁S	66,64	3,81	15,72	0,00	-0,05	0,51	0,51
N₁R	66,64	3,76	16,23	0,00	-0,05	0,51	0,51
N_1,5S	63,90	3,89	15,59	-0,16	-0,07	1,10	1,11
N_1,5R	63,74	3,82	16,69	-0,16	-0,07	1,10	1,11
N₂S	65,08	3,94	16,58	-2,70	-0,77	-0,11	2,81
N₂R	62,38	3,17	16,47	-2,70	-0,77	-0,11	2,81

Tabela V Parâmetros L*a*b* para o esmalte transparente brilhante com 3 wt% dos pigmentos sintetizados.

Amostra	L*	a*	b*	ΔL	Δa	Δb	ΔE
Z₂S	84,21	-1,58	9,18	-0,97	0,11	0,25	1,01
Z₂R	83,24	-1,47	9,43	-0,97	0,11	0,25	1,01
N_0,5S	44,56	7,05	16,32	2,66	-0,45	-2,65	3,78
N_0,5R	47,22	6,60	13,67	2,66	-0,45	-2,65	3,78
N₁S	40,82	6,60	13,67	0,69	-0,02	0,25	0,73
N₁R	41,51	6,58	13,92	0,69	-0,02	0,25	0,73
N_1,5S	44,41	5,44	14,84	-1,48	0,23	-1,17	1,90
N_1,5R	42,93	5,67	13,67	-1,48	0,23	-1,17	1,90
N₂S	51,90	4,33	17,79	-3,74	0,39	-1,18	3,94
N₂R	48,16	4,72	16,61	-3,74	0,39	-1,18	3,94

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