Treatment of Batik Industry Waste with a Combination of Electrocoagulation and Photocatalysis

This study successfully investigated the treatment of batik industry waste with a combination of electrocoagulation and photocatalysis. The use of an aluminum plate as an anode, a stainless steel 316 plate as a cathode, and titanium dioxide (TiO₂) coated on aluminum plates, the main materials in this method, resulted in the simultaneous decolorization of Remazol Red dye, elimination of 2,4,6-trichlorophenol, and reduction of hexavalent chromium (Cr[VI]). For the TiO₂ coating, a TiO₂ suspension was applied to a sanded aluminum plate. Optimal performance of the combination of electrocoagulation and photocatalysis was achieved under operating conditions of 15 V DC electric voltage, an initial pH value of 7, and the use of an aeration flow. Under the operating conditions, 600 ml batik waste containing 5 mg/L 2,4,6-trichlorophenol, 3 mg/L Cr(VI), and 390 PtCo Remazol Red dye were eliminated simultaneously within 4 hours with conversions of approximately 58%, 100%, and 97%, respectively.

2,4,6-trichlorophenol; Cr(VI); Electrocoagulation; Photocatalysis; Remazol red

Because of the philosophy behind and meaning associated with Indonesian batik, this tradition is considered an intangible cultural heritage of humanity. Since this designation by the United Nations Educational, Scientific and Cultural Organization (UNESCO), Indonesian batik has been commanding high prices around the world. Along with the increasing popularity of Indonesian batik has been a significant growth in the number and types of batik industries: from small-scale home industries to large-scale factories. This has had a negative effect on the environment. Many of the rivers near batik factories are polluted from the disposal of improperly processed industrial batik waste (Zaenuri, 2014).

Yogyakarta and Pekalongan are examples of cities that are well known for their batik industries. In an analysis of the liquid waste from the Batik Indah Yogyakarta industry, Saptarini (2009) found color waste in the amount of 324 PtCo, which was in excess of the color quality standard limit (50 PtCo, KepMen LH No.51 MENLH 1995). Although dyes do not directly have toxic effects, their by products can be categorized as dangerous substances (Brosillon et al., 2005). The total phenol content in the Bremi River in Pekalongan was found to be 0.031 mg/L (Yustiara et al., 2014), and the total chromium (Cr) was found to be 0.09 mg/L (Wijayanti et al., 2014). Phenol itself is a toxic carcinogenic compound that is very harmful to humans (Wong et al., 2011). The concentrations of heavy metals such as Cr(VI), although small, should be of concern. Aquatic organisms can absorb some of the compounds in water, and these compounds can accumulate in their bodies in as much as 100 or 1.000 times higher than the moisture content found in water (Cowen & Bruland, 1985).

Because of its diversity (color, phenolic compounds, and Cr metals), batik waste needs to be treated through a simultaneous processing method for its. This study proposed the use of a combination of electrocoagulation and photocatalysis for the simultaneous treatment of batik waste. Electrocoagulation is a continuous coagulation process that uses direct current through electrochemical events and electrolyte decomposition, with one of the electrodes being aluminum or iron (Mkpenie & Abakedi, 2015). Photocatalysis is used for degrading organic compounds, e.g., phenolic compounds and hexavalent chromium (Cr[VI]), and reducing the content of the metal ions in batik waste simultaneously with the help of ultraviolet (UV) light. Titanium dioxide (TiO₂) in the form of nanoparticles is a commonly used semiconductor in photocatalysis (Slamet et al., 2007).

Electrocoagulation enables the degradation of various types of waste, such as dyes, organic compounds, and metals. However, a great deal of electrical energy is required for processing a large amount of pollutant in a short amount of time. This will certainly affect the cost of processing. Like electrocoagulation, photocatalysis has been analyzed for its ability to degrade various types of waste. That electrocoagulation requires only UV rays has attracted a great deal of attention because of the potential for lower processing costs (Jawad et al., 2016). However, a problem with photocatalysis is its ability to process waste in shaded conditions. In such a situation, the UV rays are unable to penetrate the waste to trigger photocatalytic materials (semiconductor materials such as titanium dioxide [TiO₂]). Given the advantages and disadvantages of each process, the combination of electrocoagulation and photocatalysis has the potential for achieving the cost-effective simultaneous degradation of waste containing dyes, organic compounds, and metals in a timely manner.

The combination of electrocoagulation and photocatalysis for the simultaneous treatment of plural types of waste (dyes, organic compounds, and metals) has been rarely studied. Jati and Aviandharie (2015) performed a combination of electrocoagulation and photocatalysis to reduce Cr(VI) metal waste. Electrocoagulation was performed first; then photocatalysis was done in different containers. Escobar et al. (2016) optimized total organic carbon (TOC) removal for the treatment of lithographic wastewater by a process of electrocoagulation followed by photocatalytic. In the current study, the simultaneous processing of batik waste containing dyes, organic compounds, and metals was achieved through a combination of electrocoagulation and photocatalysis. The study thus provides an effective, environmentally friendly, and relatively low-cost method for processing batik industry plural waste. 

The simultaneous processing of mixed waste containing 2,4,6-trichlorophenol, Cr(VI), and Remazol Red dye was achieved in this study. The use of an aluminum anode, a stainless steel 316 cathode, and TiO₂ coated on an aluminum plate as a photocatalyst under operating conditions of 15 V DC electric voltage, initial pH value of 7, and the use of aeration flow was found to be optimal for the process. Under these operating conditions, 600 ml batik waste containing 5 mg/L 2,4,6-trichlorophenol, 3 mg/L Cr(VI), and 390 PtCo Remazol Red dye was eliminated simultaneously within 4 hours with conversions of approximately 58%, 100%, and 97%, respectively.

The authors acknowledge Universitas Indonesia and Kementerian Riset, Teknologi, dan Pendidikan Tinggi (KEMENRISTEKDIKTI) Republik Indonesia through the Program Kreativitas Mahasiswa-Karsa Cipta (PKM-KC) in 2017 for the financial support provided for this study. The authors would also like to show our gratitude to Mr. Muhammad Ibadurrohman from Chemical Engineering Departement, University of Indonesia for comments that greatly improved the manuscript.

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