Kinetic study on phosphate removal from aqueous solution by biochar derived from peanut shell as renewable adsorptive mediaInternational Journal of Environmental Science and Technology

About

Authors
K.-W. Jung, M.-J. Hwang, K.-H. Ahn, Y.-S. Ok
Year
2015
DOI
10.1007/s13762-015-0766-5
Subject
Environmental Chemistry / Environmental Engineering / Agricultural and Biological Sciences (all)

Text

ORIGINAL PAPER

Kinetic study on phosphate removal from aqueous solution by biochar derived from peanut shell as renewable adsorptive media

K.-W. Jung • M.-J. Hwang • K.-H. Ahn •

Y.-S. Ok

Received: 31 July 2014 / Revised: 13 November 2014 / Accepted: 27 January 2015  Islamic Azad University (IAU) 2015

Abstract As an alternative strategy for phosphate removal, biochar (black carbon) has characteristics superior to those of widely used adsorptive media, from both economic and environmental points of view. In this study, various types of biochar derived from oak wood, bamboo wood, maize residue, soybean stover, and peanut shell were tested for evaluation of phosphate removal. After 24 h of reaction time, the phosphate removal was limited (2.0–9.4 %) in case of general adsorptive media. However, interestingly, among various biochars, peanut shell-derived biochar (PSB) exhibited the best performance, showing the highest phosphate removal rate, 61.3 % (3.8 mg PO4-P g

PSB-1). We attribute this high value to the proper structural properties of PSB, such as BET-specific surface area of 348.96 m2 g-1 and mineral/phosphorus ratio (Mg/

P = 3.46 and Ca/P = 47.6). Adsorption equilibrium and kinetics of phosphate at different temperature (10, 20, and 30 C) were well explained in the whole experimental region by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The maximum adsorption capacity of PSB was 6.79 mg g-1 for phosphate at 30 C.

These findings suggest that PSB has great potential as an alternative and renewable adsorptive media for phosphate removal.

Keywords Phosphate removal  Biochar  Black carbon 

Charcoal  Peanut shells  Mineral/phosphorus ratio

Introduction

It is well known that eutrophication is one of the critical environmental problems around the world today; this process is responsible for degradation of the quality of water ecosystems, global loss of biodiversity, and negative impact on the economy. These negative effects are due to the response in water to the over enrichment of point and nonpoint nutrient (nitrogen and phosphorus) loading from natural and manmade sources (urban and agricultural runoff, animal farming) (Mainstone and Parr 2002; Smith 2003). According to one report, a nitrogen/phosphorus ratio above eight and soluble reactive phosphorus concentration below 0.3 mg L-1 means that phosphorus is likely to be a limiting factor for part of the growing season (Mainstone et al. 1995). The average nitrogen/phosphorus ratio and phosphorus concentration of the water ecosystem in the

Republic of Korea are 19.7–92.4 and 0.12 mg L-1, respectively (Kim et al. 2007). This means that controlling the phosphorus concentration is a crucial solution for preventing eutrophication.

Up to now, even though conventional wastewater treatment systems have been used to remove phosphate, these systems have not yet sufficiently solved the problem of eutrophication in the water ecosystem. Especially, conventional chemical precipitation using Ca, Al, and Fe leaded to economic burden and generation of secondary pollutants (Clark et al. 1997). Thus, the effective control

Kyung-Won Jung and Min-Jin Hwang have contributed equally to this work.

K.-W. Jung (&)  M.-J. Hwang  K.-H. Ahn

Center for Water Resources Cycle Research, Korea Institute of

Science and Technology, Hwarangno 14-gil 5, Seonbuk-gu,

Seoul 136-791, Republic of Korea e-mail: kw512@kist.re.kr

Y.-S. Ok

Department of Biological Environment, Korea Biochar Research

Center, Kangwon National University, Chuncheon 200-701,

Republic of Korea 123

Int. J. Environ. Sci. Technol.

DOI 10.1007/s13762-015-0766-5 of phosphate has been attracting a great deal of attention in the last two decades. For phosphate removal, a large number of studies have used adsorptive media such as natural products, byproducts, and man-made products (Vohla et al. 2011). Most of the adsorptive media used in these studies have had a high content of Ca, Al, and/or Fe, which are elements with strong affinity for phosphorus binding (Westholm 2006). In addition, recently, biochar derived from agricultural residue has been employed as an alternative adsorptive media (Ahmad et al. 2014; Mohan et al. 2014). Although only a few studies have investigated the ability of biochar to remove nutrients from aqueous solution, the application of biochar derived from renewable biomass is a more suitable strategy, from environmental and economic points of view, to remove phosphate and to recycle waste (Roberts et al. 2010). In this sense, up to date, various agricultural residues and other waste have been proposed as good sources for biochar production (Cao and Harris 2010; Yand and Sheng 2003; Yao et al. 2011a; Yuan et al. 2011). However, the capacity of phosphate removal highly depends on their properties of raw material and biochar; therefore, a study of the potential for phosphate removal should be required before use.

Peanuts are a widely planted legume commodity crop worldwide; approximately 34.43 million tons of peanuts were produced in 2009. Peanuts are widely used for food, oil, and medicine; they have many other uses, as well (Zhang et al. 2013). However, the main problem is the generation of waste biomass, namely peanut shells, which constitute about 30 % of peanut production (Wu et al. 2013). Most peanut shells are discarded as solid waste or are burned off in stacks, resulting in lost resources and environmental pollution; thus, there is a need to convert these shells to useful and valuable products (Ahmad et al. 2012). Therefore, if biochar derived from peanut shells can be used to remove phosphate, such a material can play a dual role in reasonable solutions to both environmental and economic issues because biochar can act as an adsorbent, as a land application for carbon sequestration, and as a valuable nutrient supplier for crops. In light of this situation, therefore, the objective of this study was to examine the feasibility of biochar derived from peanut shell for phosphate removal. As a preliminary test, five different types of biochar, oak wood, bamboo waste, maize residue, soybean stover, and peanut shells, were selected. We found that peanut shell-derived biochar (PSB) possessed the highest phosphate removal potential. In addition to monitoring the physical, chemical, and microstructural properties of biochar, we also evaluated the adsorption equilibrium and kinetic of phosphate of PSB.