Kapok fiber modified carbon nitride photocatalytic degradation of organic pollutants

doi:10.11949/0438-1157.20200304

Abstract

Abstract:

A kapok fiber (KF) modified graphite phase carbon nitride (g-C₃N₄) catalyst was prepared by a one-step pyrolysis method, and the photocatalytic degradation of organic pollutants was investigated. The structure and optical properties of KF-CN were characterized by XRD, UV-Vis DRS, TEM, PL, XPS, FT-IR and N₂ adsorption-desorption. The nitrogen adsorption-desorption isotherm results show that the presence of the mesoporous structure can improve the specific surface area of KF-CN. Elemental analysis characterization indicates the biochar modification is conductive to increase the C/N ratio of KF-CN. The XPS characterization also indicates that the introduction of carbon element can change the chemical environment of N element in the lattice of g-C₃N₄ and thus increases the electron density of N element. The photocatalytic degradation of phenol experiment was carried out to investigate the performance of as-prepared kapok fiber modified graphite carbon nitride photocatalysts by using high-pressure sodium lamp as visible light source. The results show the KF(5%)-CN(600) displayed the highest phenol degradation rate constant of 0.259 h^-1, which is 4.2 times of that of neat g-C₃N₄.The activity of KF(5%)-CN(600) does not decrease significantly after 5 cycles, hinting its excellent catalytic stability and structural stability. The possible reaction mechanism was proposed.

Key words: carbon nitride, kapok fiber, biomass, photocatalytic, degradation, catalyst

摘要：

采用一步热解法制备了木棉纤维（KF）改性的石墨相氮化碳（g-C₃N₄）催化剂，并考察了催化剂光催化降解有机污染物的性能。采用XRD、UV-Vis DRS、FT-IR、TEM、XPS、N₂吸附-脱附、PL表征对催化剂进行了结构、形貌、光学性能测试。结果表明，KF改性可以提高催化剂的比表面积，更大的比表面积可以提供更多的活性位点来参与光催化降解过程。UV-Vis DRS结果表明KF改性可以缩小催化剂的禁带宽度，提高催化剂对光能的吸收。在可见光下，KF改性的g-C₃N₄基催化剂对苯酚降解速率常数为0.259 h^-1，是纯g-C₃N₄的4.2倍，且具有优异的催化稳定性和结构稳定性。

关键词: 氮化碳, 木棉纤维, 生物质, 光催化, 降解, 催化剂

CLC Number:

TQ 028.8

LIU Shuai,LI Xuelei,LI Qimeng,WANG Yanjuan,ZHANG Jian,FENG Ruijiang,HU Shaozheng. Kapok fiber modified carbon nitride photocatalytic degradation of organic pollutants[J]. CIESC Journal, 2020, 71(12): 5530-5540.

刘帅,李学雷,李启朦,王彦娟,张健,封瑞江,胡绍争. 木棉纤维改性氮化碳光催化降解有机污染物[J]. 化工学报, 2020, 71(12): 5530-5540.

Figures/Tables 17

Table 1 The absorbance of different concentrations of phenol

浓度/(μg·g^-1)	吸光度
0	0
1	0.136
1.5	0.208
2	0.278
2.5	0.352
3	0.419
3.5	0.49
4	0.563

Fig.1 The standard curve of phenol

Fig.2 XRD pattern of different catalysts

Fig.3 FT-IR spectra of different catalysts

Fig.4 UV-Vis DRS spectra of different catalysts

Table 2 Elemental composition of as-prepared catalysts

Sample	C/% (mass)	N/% (mass)	H/% (mass)	C/N ratio
CN(600)	38.3	60.5	1.2	0.740
KF(1%)-CN(600)	38.8	59.9	1.3	0.755
KF(5%)-CN(600)	39.7	58.4	1.9	0.792
KF(10%)-CN(600)	41.3	56.3	2.4	0.858
KF(5%)-CN(550)	39.8	58.4	1.8	0.795
KF(5%)-CN(650)	40.6	57.4	2.0	0.826

Fig.5 N2 adsorption-desorption isotherms of as-prepared catalysts

Fig.6 TEM images of different catalyst

Fig.7 XPS spectra of CN(600) and KF(5%)-CN(600)

Fig.8 PL spectra of different catalysts

Fig.9 Phenol degradation performance of catalyst(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.10 The normalized rate constant ksuf of specific surface area degraded by phenol(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.11 The influence of calcination temperature of catalysts on the phenol degradation performance(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.12 Photocatalytic degradation rate of catechol and 2-chlorophenol over CN(600) and KF(5%)-CN(600)(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.13 Cyclic performance of KF(5%)-CN(600)(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.14 Capture agent’s effect on photodegradation of phenol(reaction conditions: 0.1 g catalyst, 30℃, atmospheric pressure, oxygen intake was 80 ml·min-1, 300 min)

Fig.15 Schematic diagram of mechanism of photocatalytic degradation of phenol by KF-CN

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