Enhancement of saccharin removal from aqueous solution by activated carbon adsorption with ultrasonic treatment

doi:10.1016/j.ultsonch.2004.12.007

Ultrasonics Sonochemistry

Volume 13, Issue 1, January 2006, Pages 13-18

https://doi.org/10.1016/j.ultsonch.2004.12.007 Get rights and content

Abstract

This study investigates the use of ultrasonication as a pretreatment process and its effect on the adsorption characteristics of saccharin onto activated carbon (AC). Ultrasonic decomposition of saccharin was performed at a frequency of 500 kHz under argon and O₂/N₂ (20/80 vol%) atmospheres. Adsorption was carried out using a commercial activated carbon. The behavior of total organic carbon (TOC) during ultrasonication was investigated. Saccharin removal after 180 min of ultrasonication under Ar and O₂/N₂ atmospheres are 38% and 26%, respectively, while the amount of saccharin removed by activated carbon adsorption without US pretreatment is 40% after 16 h. After 16 h of AC adsorption with 180 min of ultrasonic pretreatment under Ar and O₂/N₂ atmospheres, both removal ratios increased to 75%. These results indicated that the pretreatment of sonication under O₂/N₂ leads to the increase in the amount of saccharin adsorbed on AC. On the other hand, the TOC removal by decomposition by ultrasound is not more than 5% in both Ar and O₂/N₂ atmospheres after 180 min ultrasonication. However, the TOC removal increased to 54% and 69% after 16 h of adsorption of saccharin pretreated by ultrasonication for 180 min under Ar and O₂/N₂ atmospheres, respectively. About 13% and 16% TOC removal in Ar and in O₂/N₂, respectively, were achieved due to adsorption of the by-products. It is considered that the improvement in TOC removal is also brought about by the formation of the by-products that were adsorbed onto AC.

Introduction

From the nickel plating process, plating wastewater is discharged after dragging out plating products or rinsing off residues on the surface of plating products. This wastewater contains harmful compounds such as boric acid (H₃BO₃) and nickel, and organics such as saccharin used as a brightener. In accordance with severe regulation for wastewater discharge in recent years, it is urgently required that the harmful chemical components are removed from wastewater discharged from the process. Instead of removing the harmful compounds from the wastewater discharged from the plating process, it is preferable to reuse the solution containing boron and nickel for plating. However, it is known that the presence of organics lowers the quality of products if reused. Before reusing the solution containing boric acid, nickel and organics such as saccharin, it is necessary to remove the organics from the solution. Various technologies have been employed for wastewater treatment containing organic components. These include biodegradation, chemical oxidation, wet oxidation, ultrasonic irradiation, ultraviolet irradiation, and adsorption over suitable materials such as activated carbon.

Ultrasonic irradiation is considered as one of the techniques in advanced oxidation processes (AOP) [1]. Ultrasonic degradation is augmented by thermal decomposition and mixing effect. Ultrasound, with frequencies roughly between 20 kHz and 10 MHz, has a drastic effect on chemical reactions. The mechanism that causes this effect is known as acoustic cavitation: formation, growth and collapse of cavitation bubbles in a liquid [2]. The application of ultrasound for the degradation of organic contaminants such as petroleum hydrocarbons, chlorinated hydrocarbons, and aromatic compounds has already been experimented and reported by several researchers [3], [4], [5], [6], [7], [8], [9], [10].

Activated carbon adsorption on the other hand, is an important separation technology [11] which is widely used for drinking water purification and is increasingly applied in industrial wastewater treatment [12]. Activated carbons have also been employed to remove organic contaminants from wastewater. Activated carbon is effective for adsorbing many types of chemicals but it is especially known for its power in adsorbing organic compounds due to its non-polar nature. For instance, the adsorption of phenol and substituted phenols from aqueous solution on activated carbons has been intensively investigated for decades [13], [14], [15]. Likewise, activated carbon adsorption has been widely utilized for the removal of dyes from aqueous solutions and from dyeing industry wastewater [12], [16], [17] and for the decolorization of wastewater from fermentation industry [18].

In this study, the combination of ultrasonication (US) and activated carbon (AC) adsorption is considered. The major advantage expected from this is increased efficiency of adsorption by reforming the chemical substance using ultrasound. Li et al. [19] and Hamdaoui et al. [20] investigated the effects of ultrasound on the adsorption of phenol on polymeric resin and p-chlorophenol on granular activated carbon, respectively. Their results indicated that the adsorption of the phenolic compounds determined in the presence of ultrasound is less than that in the absence of ultrasound. In their studies, ultrasound was applied after the adsorption system had reached a state of equilibrium. In our study, we performed pretreatment by ultrasonication of saccharin in aqueous solution and conducted further treatment by activated carbon adsorption. We compared the results with that of treatment of saccharin by activated carbon adsorption alone. Our main objective is to investigate the effect of ultrasonication as a pretreatment process on the removal of saccharin and organic by-products by activated carbon adsorption.

Section snippets

Materials

Commercial grade saccharin (C₇H₄NNaO₃S · 2H₂O; MW = 241.19 g/mole) was employed as a model pollutant and commercial activated carbon (Kintal WA) was used as adsorbent. The activated carbon, obtained from Cataler Corporation, is made from coconut shell and has a surface area of 1100 m²/g and 8–32 mesh. The activated carbon particles were sieved and particle size fraction less than 850 μm was used for the study. The saccharin was dissolved in distilled water to prepare 100 mg/l aqueous solution. All

Removal of saccharin

Ultrasonic treatment of 200 ml sample solution was done with a time range of 30–180 min. The HPLC chromatogram of the initial saccharin solution showed only one peak, which implies that there were no impurities. After each treatment, a small sample was taken for HPLC analysis. The saccharin peak decreased with increasing sonication time indicating the decrease in saccharin concentration in the solution. Fig. 2 shows the saccharin removal as a function of sonication time. The figure shows a

Conclusions

The effect of ultrasonic pretreatment on the removal of organics component such as saccharin by activated carbon adsorption was studied. At 180 min, only 4% TOC is removed when using ultrasonication alone in Ar and O₂/N₂ atmospheres, respectively, and 40% when using activated carbon adsorption alone. The amount of saccharin adsorbed onto AC increased to 49% after 16 h of adsorption with ultrasonication pretreatment in O₂/N₂ atmosphere. This is probably due to pH changes. When the sample solution

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Enhancement of saccharin removal from aqueous solution by activated carbon adsorption with ultrasonic treatment

Abstract

Introduction

Section snippets

Materials

Removal of saccharin

Conclusions

Ultrason. Sonochem.

Ultrason. Sonochem.

Ultrason. Sonochem.

Ultrason. Sonochem.

Ultrason. Sonochem.

Water Res.

Sep. Purif. Tech.

Chem. Eng. J.

Carbon

Carbon

Carbon