Abstract
Rice straw, an agricultural waste product generated in huge quantities worldwide, is utilized to remediate diesel pollution as it possesses excellent characteristics as a natural sorbent. This study aimed to optimize factors that significantly influence the sorption capacity and the efficiency of oil absorption from diesel-polluted seawater by rice straw (RS). Spectroscopic analysis by attenuated total reflectance infrared (ATR-IR) spectroscopy and surface morphology characterization by variable pressure scanning electron microscopy (VPSEM) and energy-dispersive X-ray microanalysis (EDX) were carried out in order to understand the sorbent capability. Optimization of the factors of temperature pre-treatment of RS (90, 100, 110, 120, 130 or 140 °C), time of heating (10, 20, 30, 40, 50, 60 or 70 min), packing density (0.08, 0.10, 0.12, 0.14 or 0.16 g cm−3) and oil concentration (5, 10, 15, 20 or 25% (v/v)) was carried out using the conventional one-factor-at-a-time (OFAT) approach. To eliminate any non-significant factors, a Plackett–Burman design (PBD) in the response surface methodology (RSM) was used. A central composite design (CCD) was used to identify the presence of significant interactions between factors. The quadratic model produced provided a very good fit to the data (R2 = 0.9652). The optimized conditions generated from the CCD were 120 °C, 10 min, 0.148 g cm−3 and 25% (v/v), and these conditions enhanced oil sorption capacity from 19.6 (OFAT) to 26 mL of diesel oil, a finding verified experimentally. This study provides an improved understanding of the use of a natural sorbent as an approach to remediate diesel pollution.
Highlights
Sorbents are either adsorbent or absorbent materials
The current study focused on the use of rice straw (RS) as a natural sorbent to remediate dieselpolluted seawater in a designed filter system, optimizing the conditions of its use through the conventional one-factor-at-a-time (OFAT) approach followed by the response surface methodology (RSM)
The analyses carried out identified that various factors could enhance the effectiveness of RS as a natural sorbent
Summary
Sorbents are either adsorbent or absorbent materials. Their purpose is to bind target substances, such as liquid oil, in a solid or semisolid matrix. Sorbents can be classified as natural or synthetic materials. Synthetic sorbents are mostly made from polypropylene fibers that are not environmentally friendly and often lead to secondary contamination [1]. Natural organic materials such as moss, straw, sawdust, coco peat, cogon grass, cotton and hay can be used as sorbents [2,3,4,5]. The high levels of generation of agricultural wastes strengthen the relevance of using natural sorbents to remediate contaminated sites, in the case of diesel contamination
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