咖啡渣活性炭的制备、表征及其对Cr(Ⅵ)的吸附机制研究

doi:10.3969/j.issn.1673-5854.2020.04.001

摘要/Abstract

摘要：

以碘吸附值为评价指标，活化时间、活化温度和浸渍比为影响因素，采用响应面法试验设计对磷酸活化法制备咖啡渣活性炭的工艺条件进行优化，并通过静态吸附试验研究了不同吸附时间、溶液pH值和吸附温度条件下，活性炭对水溶液中Cr（Ⅵ）吸附性能的影响，最后利用Langmuir、Freundlich吸附等温方程、准一级动力学方程、准二级动力学方程和颗粒内部扩散方程进行拟合。试验结果表明，制备咖啡渣活性炭的最佳工艺条件为活化时间1 h、活化温度498℃、浸渍比1.72；在此条件下活性炭得率为30.4%，碘吸附值为（799±16）mg/g，比表面积为1 006 m²/g，孔容为0.779 cm³/g、微孔孔容为0.051 cm³/g、平均孔径为3.088 nm。较低pH值和较高温度能够促进活性炭对Cr（Ⅵ）的吸附；Langmuir等温方程能够更好地描述活性炭对Cr（Ⅵ）的吸附效果；活性炭对Cr（Ⅵ）的吸附分3个阶段：快速吸附阶段、慢速吸附阶段和吸附平衡阶段，10 min内可完成吸附总量的79%，360 min内达到吸附平衡，该吸附过程符合准二级吸附动力学方程。分析表明咖啡渣活性炭对Cr（Ⅵ）的吸附主要为单分子层的化学吸附。

关键词: 咖啡渣, 响应面, 活性炭, Cr(Ⅵ), 吸附性能

Abstract:

The preparation conditions of activated carbon from coffee grounds, including activation temperature, activation time and impregnation ratio, were studied by using the response surface methodology with iodine adsorption value as evaluation index. And the effects of adsorption time, initial pH value and temperature on the Cr(Ⅵ) removal by the obtained activated carbon were investigated. In addition, the kinetic data were fitted by pseudo-first-order equation, pseudo-second-order equation and infra-particle diffusion model, and the equilibrium data was analyzed by using Langmuir and Freundlich isotherm models. The experimental results showed that the activated carbon had the best performance under the optimum conditions of activation time 1 h, activation temperature 498℃ and impregnation ratio 1.72. Under these conditions, the yield of activated carbon was 30.4%, and the iodine adsorption value got up to (799±16) mg/g, the relative surface area could reach 1 006 m²/g, the total pore volume was 0.799 cm³/g, the t-Plot micropore volume was 0.051 cm³/g and the average pore size was 3.088 nm. The adsorption data fitted Langmuir isotherm model. Higher temperature and lower pH could promote the adsorption of Cr(Ⅵ) on activated carbon. The adsorption of Cr(Ⅵ) on activated carbon was divided into three stages:fast adsorption stage, slow adsorption stage and adsorption equilibrium stage, the total adsorption of 79% was completed in 10 min, the adsorption process could reach equilibrium in 360 min, and the pseudo-second-order equation generated the best agreement with the experimental data for the adsorption systems. The results showed that the adsorption of Cr(Ⅵ) on the obtained activated carbon was chemical adsorption with monomolecular layer.

Key words: coffee grounds, response surface methodology, activated carbon, Cr(Ⅵ), adsorption properties

中图分类号:

TQ35

任杰,万力,陈楠纬,杨帆,孙水裕,任随周. 咖啡渣活性炭的制备、表征及其对Cr(Ⅵ)的吸附机制研究[J]. 生物质化学工程, 2020, 54(4): 1-8.

Jie REN,Li WAN,Nanwei CHEN,Fan YANG,Shuiyu SUN,Suizhou REN. Preparation and Characterization of Activated Carbon from Coffee Grounds and Its Adsorption Mechanism for Cr(Ⅵ)[J]. Biomass Chemical Engineering, 2020, 54(4): 1-8.

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序号 No.	X₁ 活化时间/h activation time	X₂ 活化温度/℃ activation temperature	X₃ 浸渍比值 dipping ratio	碘吸附值iodine adsorption value/(mg·g^-1)
序号 No.	X₁ 活化时间/h activation time	X₂ 活化温度/℃ activation temperature	X₃ 浸渍比值 dipping ratio	实测值 actual value	预测值 expected value
1	1	350	1	543.31	543.00
2	0.5	450	1	678.57	686.78
3	1	450	1.5	769.72	775.13
4	0.5	550	1.5	762.08	757.72
5	0.5	350	1.5	508.72	501.23
6	1	350	2	576.72	580.57
7	1	450	1.5	780.00	775.13
8	1.5	350	1.5	603.39	607.75
9	0.5	450	2	701.54	705.18
10	1.5	550	1.5	711.39	718.88
11	1.5	450	1	699.05	695.40
12	1	550	1	724.62	720.77
13	1	450	1.5	763.212	775.13
14	1.5	450	2	772.43	764.23
15	1	550	2	769.32	770.03
16	1	450	1.5	783.61	775.13
17	1	450	1.5	779.14	775.13

方差来源 source	平方和 sum of squares	自由度 degree of freedom	均方 mean square	F值 F value	P值 P value	显著性¹⁾ significant
模型model	128612.70	9	14290.3	160.10	< 0.0001	**
X₁	2289.75	1	2289.75	25.65	0.0015	**
X₂	67574.07	1	67574.07	757.07	< 0.0001	**
X₃	3804.54	1	3804.54	42.62	0.0003	**
X₁X₂	5281.80	1	5281.80	59.17	0.0001	**
X₁X₃	635.54	1	635.54	7.12	0.0321	*
X₂X₃	31.85	1	31.85	0.36	0.5691
X₁²	5060.26	1	5060.26	56.69	0.0001	**
X₂²	37261.34	1	37261.34	417.46	< 0.0001	**
X₃²	3200.71	1	3200.71	35.86	0.0005	**
残差residual	624.80	7	89.26
失拟项lack of fit	341.92	3	113.97	1.61	0.3202
纯误差pure error	282.88	4	70.72
总和total	129237.5	16

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