Elsevier

Powder Technology

Volume 326, 15 February 2018, Pages 181-189
Powder Technology

Net-like porous activated carbon materials from shrimp shell by solution-processed carbonization and H3PO4 activation for methylene blue adsorption

https://doi.org/10.1016/j.powtec.2017.12.034Get rights and content

Highlights

  • Net-like porous of PS-Ac was developed by carbonization and H3PO4 activation.

  • The surface of PS-Ac possessed abundance of phosphate, hydroxyl and carboxyl groups.

  • PS-Ac exhibited excellent effect for MB dyes with qmax of 828 mg g 1.

  • Mechanism for MB adsorption on PS-Ac was elucidated.

Abstract

In this work, shrimp shell waste was used as a novel precursor for the production of a net-like porous activated carbon by solution-processed carbonization and chemical activation with phosphoric acid (H3PO4). The H3PO4 activation of activated carbon from shrimp shell (PS-Ac) was characterized in terms of textural, surface and morphological properties by N2 sorption, Raman, HR-TEM and SEM-EDS analyses. It showed that PS-Ac was a net-like porous material with mesoporous structures. The average pore size and BET surface area were 4.5 nm and 560.6 m2 g 1, respectively. The obtained PS-Ac was then employed for the adsorption of methylene blue (MB) dyes and systematically investigated the effect of solution pH, initial concentration, contact time and temperature for MB adsorption. Experimental data were well described by the Langmuir isotherm and the pseudo-second order model with the maximum adsorption capacity of 826 mg g 1(MB), which showed to be high compared to other ACs reported in the literature. Thermodynamic parameters indicated that PS-Ac for MB adsorption process was spontaneous and endothermic. Moreover, coupled with experimental results, FT-IR and XPS analysis suggested that the adsorption mechanism of MB onto PS-Ac was possible attributed to electrostatic interaction between the surface of functional groups (single bondPO43 , single bondCOO, single bondOsingle bond) on adsorbent and the cation ions MB-N+ in the basic solution.

Introduction

Activated carbon is a remarkably adsorbent material with a large number of applications in the remediation of contaminated groundwater and industrial wastes because of its high porosity and surface area, wonderful structures and easy availability [1], [2]. A major challenge of adsorption process is the high production cost of activated carbons, which has resulted to a growing research at reducing the production cost. Recently, low cost alternative precursors have been paid much attention to produce carbonaceous materials from the viewpoint of economic, environmental and societal issues, such as biomass, agricultural residues and shells [3], [4], [5]. Among of those precursors, shrimp shell is an attractive resource since these industries have undergone a dramatic increase in recent years and enormous amount of shrimp shell waste is produced in the processing of shrimps [6]. The exoskeleton and cephalothorax from the shrimp shell waste, accounts to the 50–70% of the total weight, are known to contain high biological value components such as protein, chitin and astaxanthin [7]. However, a small part of the waste is used as chicken feed and for recovery of bioactive compounds [8]. Moreover, the chitin, as the main components in shrimp shell, is the second most important natural long-chain polymer in the world and can be easy formed net-like structure materials by cross-linking reaction [8]. Therefore, research on the use of shrimp shell waste for the production of a novel activated carbon is a welcome development as it would be served as a cheap alternative precursor as well as solving the problem of environmental sustainability and reducing the cost of waste management.

The adsorptive properties of activated carbon depend on their high surface area, well-developed internal pore structure and surface chemical functional groups located at the outer and inner surfaces. These properties lie on the preparation method as well as the precursor material. Contrary to conventional carbonization process achieved by high-temperature heating treatment in inert atmosphere, solution-processed carbonization is more favorable to tailor the surface chemistry of resultant products due to its lower temperature, easier to obtain small molecules and carbon rich solid product [9]. On the other hand, in contrast to physical activation, chemical activation achieved by using activating agents is a double-step, controllable and effective method for activated carbons with developed porosity [10]. Among many activated agents, phosphoric acid has been widely employed for preparing of activated carbons materials by many researchers since the presence of H3PO4 in the interior of the precursor not only can restrict the formation of tar species and inhibit the shrinkage of the particle but also supply abundant phosphorus groups on the surface of activated carbons [11], [12].

Therefore, in this study, a synthetic procedure for the preparation of activated carbon from shrimp waste was designed by solution-processed carbonization and H3PO4 activation (PS-Ac). The resultant PS-Ac material was characterized by N2 sorption, Raman, HR-TEM, SEM-EDS, FT-IR and XPS. The efficiency of the prepared PS-Ac was carried out by using methylene blue (MB) as the model adsorbate. Adsorption experiments for the effect functions on the adsorption capacity of MB, including pH, contact time, initial concentration and temperature, were systematically investigated. The data of these experiments were evaluated and fitted by various adsorption kinetic and isotherm models.

Section snippets

Materials

Shrimp shell was provided by Shanghai Weikang Biological Co. Previous to phosphorylation process, shrimp shell was washed thoroughly with deionized water to remove adhering dust, salt and parts of metal impurities. After drying at 110 °C, these precursors were finely ground into small pieces. Methylene blue (MB), which is a cation dye, used to investigate the adsorption capacity of the prepared PS-Ac was purchased from Sigma-Aldrich. Dye stock solution (1000 mg L 1) was prepared by dissolving 0.10 

Texture properties of PS-Ac

The N2 adsorption-desorption isotherms and the pore size distribution for PS-Ac at 77.4 K were presented in Fig. 1A. As can be seen in Fig. 1A, (i) the adsorption isotherms demonstrated a sharp rise and convex curve at low relative pressure ratios because of the strong interactions on the adsorbates surfaces; (ii) Immediately, it was appearance of isotherm inflection point and a monolayer adsorption; (iii) Then, the multilayer adsorption gradually formed and saturated vapor pressure with the

Conclusion

Activated carbons with a net-like porous and excellent MB adsorption performance have been prepared from the shrimp shell waste through coupling with low temperature carbonization and H3PO4 activation. Kinetic and isotherm model analysis the adsorption of MB on PS-Ac indicated that the experimental data were well described by the pseudo-second order model and Langmuir isotherm with the remarkable maximum adsorption capacity of 826 mg g 1; and the adsorption process was spontaneous and

Acknowledgement

We are grateful for the financial support by National Natural Science Foundation of China (Grant No. 21407050) and the Fundamental Research Funds for the Central Universities (Grant No. 22A201514019).

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