Thermodynamic and Kinetic Adsorption of Cr(Ⅵ) on Hydrochars and the Effect of Hydrothermal Time

Abstract

Abstract:

The agricultural wastes of peanut shells were used as carbonaceous material precursors, which were heated under the hydrothermal temperature of 200 ℃ and kept for the desired time duration of 1 h, 5 h or 10 h to prepare the hydrochars for the removal of Cr(Ⅵ) from aqueous solution. According to FT-IR spectrum, elemental analysis and SEM characterization of hydrochar samples, the results showed that hydrothermal carbonization method is feasible for porous carbon-based hydrochars, and the aromaticity increases with hydrothermal time, while the yield and the polar functional groups decrease.These properties would affect the adsorption performance of hydrochars. The batch experiments showed that the adsorption kinetics of Cr(Ⅵ) on hydrochars followed the pseudo-second-order model and the Freundlich model well fitted the isothermal adsorption. According to thermodynamic study, such sorption behavior belongs to a preferential easy process, which is also a spontaneous, endothermic and physical adsorption. The adsorption capacity of Cr(Ⅵ) on hydrochars were enhanced with the hydrothermal time on biomass of peanut shells. Therefore, hydrochars could be applied as an economic adsorbent in water remediation. The present study could also provide an important practical value for the comprehensive utilization of agricultural wastes.

Key words: biomass, hydrochar, hydrothermal time, adsorption, Cr(Ⅵ)

CLC Number:

P595
X142

LIU Yuyan, ZHOU Jingyao, MA Shaoqiang, CHEN Jiawei. Thermodynamic and Kinetic Adsorption of Cr(Ⅵ) on Hydrochars and the Effect of Hydrothermal Time[J]. Geoscience, 2017, 31(05): 1039-1045.

Figures/Tables 9

Fig.1 Product yield and morphology of hydrochars (A) Effect of hydrothermal time on the yield; (B) SEM image of the sample HC(5 h)

Fig.2 Elements analysis of peanut hull biomass and hydrochars (A) Elemental composition;(B) H/C-O/C atomic ratio

Fig.3 FTIR characterization of samples (A) Biomass and hydrochars; (B) HC(5 h) before and after adsorption of Cr(Ⅵ)

Fig.4 Sorption kinetics of Cr(Ⅵ) on hydrochars (A)Pseudo-first-order model; (B) Pseudo-second-order model

Table 1 Pseudo-first-order and pseudo-second-order kinetic parameters for the sorption of Cr(Ⅵ) on hydrochars

水热炭	平衡吸附量	准一级动力学方程					准二级动力学方程
水热炭	平衡吸附量	q_e	k₁		R²		q_e	k₂	R²
HC(1 h)	4.14	3.827		0.280		0.818	4.61	0.037	0.981
HC(5 h)	9.42	8.411		0.757		0.847	9.90	0.03	0.992
HC(10 h)	10.35	8.835		0.962		0.838	10.00	0.031	0.992

Fig.5 Isothermal adsorption of Cr(Ⅵ) on hydrochars (A) Freundlich model; (B) Langmuir model

Table 2 Model parameters of isothermal adsorption of Cr(Ⅵ) on hydrochars

水热炭	Freundlich				Langmuir
水热炭	k_f	n	R²		q_m		b		R²
HC(1 h)	1.420	0.496	0.980	54.632		0.002 87		0.923
HC(5 h)	2.379	0.429	0.980	50.46		0.004 64		0.904
HC(10 h)	4.789	0.343	0.946	51.21		0.008 07		0.873

Fig.6 Isothermal adsorption of Cr(Ⅵ) on sample HC(5 h) at different temperatures

Table 3 Thermodynamic parameters for adsorption of Cr(Ⅵ) on sample HC(5 h)

ΔG⁰				ΔH⁰	ΔS⁰
290 K	300 K	310 K		25.98	0.1
-2.12	-2.17	-4.05		25.98	0.1

References 21

[1]	孙克静, 张海荣, 唐景春, 等. 不同生物质原料水热生物炭特性的研究[J]. 农业环境科学学报, 2014, 33(11): 2260-2265.
[2]	LEHMANN J, RILLIG M C, THIES J, et al. Biochar effects on soil biota-A review[J]. Soil Biology and Biochemistry, 2011, 43(9): 1812-1836. DOI URL
[3]	MARRIS E. Putting the carbon back: Black is the new green[J]. Nature, 2006, 442: 624-626. DOI
[4]	MALIK P K. Use of activated carbons prepared from sawdust and rice-husk for adsorption of acid dyes: a case study of Acid Yellow 36[J]. Dyes and Pigments, 2003, 56(3): 239-249. DOI URL
[5]	安增莉, 侯艳伟, 蔡超, 等. 水稻秸秆生物炭对Pb(Ⅱ)的吸附特性[J]. 环境化学, 2011, 30 (11): 1851-1857.
[6]	CHEN B L, CHEN Z M. Sorption of naphthalene and 1-naphthol by biochars of orange peels with different pyrolytic temperatures[J]. Chemosphere, 2009, 76(1):127-133. DOI PMID
[7]	JIANG J, XU R K. Application of crop straw derived biochars to Cu(Ⅱ) contaminated Ultisol: Evaluating role of alkali and orga-nic functional groups in Cu(Ⅱ) immobilization[J]. Bioresource Technology, 2013, 133: 537-545. DOI URL
[8]	HAN Y T, CAO X, OUYANG X, et al. Adsorption kinetics of magnetic biochar derived from peanut hull on removal of Cr (Ⅵ) from aqueous solution: Effects of production conditions and particle size[J]. Chemosphere, 2016, 145: 336-341. DOI URL
[9]	LIU Z G, ZHANG F S. Removal of lead from water using biochars prepared from hydrothermal liquefaction of biomass[J]. Journal of Hazardous Materials, 2009, 167:933-939. DOI PMID
[10]	BEESLEY L, MARMIROLI M. The immobilisation and retention of soluble arsenic, cadmium and zinc by biochar[J]. Environmental Pollution, 2011, 159(2): 474-480. DOI PMID
[11]	WILSON J A, PULFORD I D, THOMAS S. Sorption of Cu and Zn by bone charcoal[J]. Environmental Geochemistry and Health, 2003, 25(1): 51-56. PMID
[12]	SOLDATKINA L M, SAGAIDAK E V, MENCHUK V V. Adsorption of cationic dyes from aqueous solutions on sunflower husk[J]. Journal of Water Chemistry and Technology, 2009, 31(4): 238-243. DOI URL
[13]	吴艳姣, 李伟, 吴琼, 等. 水热炭的制备、性质及应用[J]. 化学进展, 2016, 28(1): 121-130. DOI
[14]	ZHAI Y B, LIU X M, ZHU Y, et al. Hydrothermal carbonization of sewage sludge: The effect of feed-water pH on fate and risk of heavy metals in hydrochars[J]. Bioresource Technology, 2016, 218: 183-188. DOI PMID
[15]	DONAR Y O, ÇAĞLAR E, SINAĞ A. Preparation and characterization of agricultural waste biomass based hydrochars[J]. Fuel, 2016, 183:366-372. DOI URL
[16]	曹茜, 陈家玮. 溶解氧对零价铁去除水中六价铬的影响[J]. 现代地质, 2013, 27(2):435-439.
[17]	SEVILLA M, FUERTES A B. Chemical and structural properties of carbonaceous products obtained by hydrothermal carbonization of saccharides[J]. Chemistry-A European Journal, 2009, 15 (16):4195-4203. DOI PMID
[18]	WIEDNER K, NAISSE C, RUMPEL C, et al. Chemical modification of biomass residues during hydrothermal carbonization-What makes the difference, temperature or feedstock?[J]. Organic Geochemistry, 2013, 54:91-100. DOI URL
[19]	CHINGOMBE P, SAHA B, WAKEMAN R J. Sorption of atrazine on conventional and surface modified activated carbons[J]. Journal of Colloid and Interface Science, 2006, 302 (2): 408-416. PMID
[20]	BANSAL M, SINGH D, GARG V K. A comparative study for the removal of hexavalent chromium from aqueous solution by agriculture wastes’ carbons[J]. Journal of Hazardous Materials, 2009, 171: 83-92. DOI URL
[21]	ZHANG J Y, WU C D, JIA A Y, et al. Kinetics, equilibrium and thermodynamics of the sorption of P-nitrophenol on two variable charge soils of Southern China[J]. Applied Surface Science, 2014, 298 (8): 95-101. DOI URL