Elsevier

Journal of Hazardous Materials

Volume 186, Issue 1, 15 February 2011, Pages 526-532
Journal of Hazardous Materials

Study of oil sorption behavior of filled and structured fiber assemblies made from polypropylene, kapok and milkweed fibers

https://doi.org/10.1016/j.jhazmat.2010.11.031Get rights and content

Abstract

This article reports on oil sorption behavior of fiber assemblies made up of single natural and synthetic fibers as well as blend of natural and synthetic fibers when tested with high density oil and diesel oil. A series of filled fiber assemblies were prepared from 100% polypropylene, kapok, and milkweed fibers and another series of bonded structured fiber assemblies were prepared from a 70/30 blend of kapok and polypropylene fibers and a 70/30 blend of milkweed and polypropylene fibers. It was observed that the porosity of the fiber assemblies played a very important role in determining its oil sorption capacity. The polypropylene fiber assembly exhibited the highest sorption capacity (g/g) followed by the kapok and milkweed fiber assemblies at porosity <0.98. At higher porosities (above 0.98), polypropylene filled fiber assembly has poor sorption capacity due to large sized inter fiber pore. The kapok and milkweed fibers have intra fiber porosities of 0.81 and 0.83, respectively. All the fiber assemblies showed higher oil sorption capacity with the high density oil as compared to the diesel oil. As the kapok and milkweed fiber have low cellulose content, hence their slow degradation is an advantage in fresh and marine water applications. The good sorption capacity of kapok and milkweed fiber assemblies along with their bio-degradable nature offer great scope for structuring them into fiber assemblies with large porosity and uniform pores to have efficient oil sorbents.

Research highlights

▶ In this study, we compare the oil (high density oil and diesel oil) sorption behaviour of filled and structured fiber assemblies made from single natural (kapok and milkweed) and synthetic fibers (polypropylene) as well as blends of natural and synthetic fibers. ▶ We analyze the results in terms of porosity and hydraulic pore diameters of the fiber assemblies and concluded that higher is the porosity higher is the oil sorption capacity. ▶ The natural fiber assemblies are found to have good sorption capacity, but this is lower as compared to that of polypropylene, especially when the porosity is less than 0.98. ▶ The natural fibres have low cellulose content which offers them slow biodegradability and they might be found as interesting sorbents for marine and freshwater applications.

Introduction

Oil is known to be one of the most important sources of energy in the modern industrial world. It is also used as a raw material for many chemicals and synthetic polymers worldwide [1], [2], [3]. It is a naturally occurring substance. The organic residues from the decay of plants and animals are converted by heat and pressure into petroleum, migrating upwards, sometimes over extensive areas, either to reach the surface or be occasionally trapped in what are to become oil reservoirs [4]. During production, transportation, storage, and usage of oil there is always a risk of oil spillage. Oil spill occurs over the seas, water bodies and land surfaces due to tanker disasters, wars, operation failures, equipment breaking down, accidents, and natural disasters. Oil spills into land, river or ocean impose a major problem on the environment [2], [5], [6], [7], [8], [9], [10]. The impact of marine oil spills to coastal environments and marine resources has over the past decades created increased public and government awareness and concern to preserve and protect the marine environment [11]. When oil comes in contact with water, it forms oil-in-water emulsion or floating film that needs to be removed before it is discharged into the environment. Even very low concentrations of oils can be toxic to microorganisms responsible for biodegradation in conventional sewage processes [12]. The volatile components evaporate quickly. Some of the medium-sized polycyclic aromatic hydrocarbons are slightly soluble. Some of the products, which are degraded by sun and microorganisms, are highly soluble. The polycyclic aromatic hydrocarbons are known to affect a variety of biological processes and can be potent cell mutagens and carcinogens [3]. It is therefore necessary to clean the water or land immediately after the oil spill. The removal of crude oil and petroleum products that are spilled at sea is a serious problem of the last few decades. There are some oil spill remediation products available including but not limiting to dispersants, absorbents, bioremediation agents and other miscellaneous products like surface cleaners, gelling agents, demulsifiers, solidifiers, etc. that can be used to clean up oil spill. Of them, the polypropylene fiber based oil sorbent products have been found to be mostly used to clean up oil spill. Polypropylene is however not biodegradable, hence possess environmental problems. Instead the natural fiber based oil sorbents could be an interesting alternative to the synthetic oil sorbents.

Abdullah et al. studied the physicochemical and sorption characteristics of Malaysian kapok with diesel and engine oil. Kapok exhibited high hydrophobic–oleophilic characteristics, attributed to hollow lumen and its waxy surfaces. Kapok also found to have high oil retention and re-usability [13]. Milkweed floss has been reported to have hollow structure that provides large interspatial area to trap and retain oil [14]. Kapok fibers typically comprise of 64% cellulose, 13% lignin [15] and milk weed fiber comprise of 55% cellulose, 18% lignin [16]. Besides these constituents, they also contain waxy cutin on the fiber surface which makes them water repellent notwithstanding they are mainly composed of cellulose. Suni et al. have studied the oil sorption characteristics of cotton grass fiber. Cotton grass fibers and mats exhibited high sorption capacity of different oils than synthetic sorbent. Because of slow bio-degradability of these fibers, it would be easy to dispose the used sorbent either by composting or burning [17]. In this work, an attempt has been made to develop fiber assemblies with different porosities made up of single natural (Kapok and Milkweed) and synthetic fibers (Polypropylene) as well as blends of natural and synthetic fibers to study the influence of porosity and types of fibers and oils on oil sorption behavior.

Section snippets

Materials

In this work, three different fibers namely kapok, milkweed and polypropylene were used. The oils used were high density oil and diesel oil. The density of the high density oil and diesel oil was 0.9 g cm−3 and 0.82 g cm−3, respectively. The surface tension of the high density oil and diesel oil was 3.1 × 10−2 cN cm−1 and 2.5 × 10−2 cN cm−1, respectively. The viscosity of the high density oil and diesel oil was 1.17 × 10−3 cN s cm−2 and 1.64 × 10−5 cN s cm−2 at 20 °C temperature. The kapok fiber was collected from

Fiber structure

The scanning electron microscopic images of the cross-section of kapok, milkweed, and polypropylene fibers are shown in Fig. 1. It can be observed that the kapok and milkweed fibers are hollow fibers. Similar observations were made earlier [20], [21]. The inner and outer diameters of the kapok fiber were measured as 20.7 μm and 23 μm, respectively. The same for the milkweed fiber were measured as 26.5 μm and 29 μm, respectively. The diameter of the polypropylene fiber was measured as 19 μm. The

Conclusions

The fiber assemblies made from kapok and milkweed have good oil sorption capacity but lower compared to that of polypropylene. Due to low cellulose content in these natural fibers, they might be interesting sorbent for marine and freshwater applications as they cannot easily degraded by cellulose degrading microbes. The porosity of a fiber assembly played a very important role in determining its oil sorption capacity. The higher is the porosity the higher is the oil sorption capacity. By

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