Enhancing Photocatalytic Degradation of Methylene Blue Using ZnO/Carbon Dots Nanocomposite Derived From Coffee Grounds
Akhiruddin Maddu 1  
,   Reny Meliafatmah 1  
,   Erus Rustami 1  
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Department of Physics, Bogor Agricultural University (IPB University), Jl. Meranti, Gedung Wing S, Kampus IPB Dramaga, Bogor 16680, Indonesia
Akhiruddin Maddu   

Department of Physics, Bogor Agricultural University, Jalan Meranti, Kampus Dramaga, 16680, Bogor, Indonesia
Submission date: 2019-12-09
Final revision date: 2020-02-23
Acceptance date: 2020-04-06
Online publication date: 2020-07-31
Publication date: 2020-10-05
Pol. J. Environ. Stud. 2021;30(1):273–282
In this article, we report the enhancement of the photocatalytic activity of ZnO/carbon dots (CDs) nanocomposite in degrading methylene blue (MB) dye. Carbon dots (CDs) were synthesized by a hydrothermal method utilizing coffee grounds as a carbon source. ZnO/CDs nanocomposite was synthesized by a single-step and in-situ sonochemical process. The particle size of CDs measured by dynamic light scattering (DLS) was found at about 7.7 nm. The result of X-ray diffraction analysis confirmed that the hexagonal wurtzite structure of ZnO nanoparticle has a small crystal size and the lattice parameters decreasing due to CDs addition. The surface morphology images were taken by scanning electron microscopy (SEM) shows a very fine particle both for pure ZnO nanoparticle and ZnO/CDs nanocomposite. The result of Energy Dispersive X-Ray Spectroscopy (EDXS) analysis confirmed the presence of the carbon element in the ZnO/CDs nanocomposite indicated that the nanocomposite has been formed. The result of the photocatalytic test showed that the ZnO/CDs nanocomposite photocatalyst had significantly increased photocatalytic activity compared to the pure ZnO nanoparticle photocatalyst. ZnO/CDs nanocomposite photocatalyst resulted in a photodegradation rate three times higher than pure ZnO nanoparticle photocatalyst and nine times higher than the photolysis treatment (without photocatalyst). Whereas the degradation efficiency of MB using ZnO/CDs nanocomposite photocatalyst was twice higher than using pure ZnO nanoparticles and four times higher than photolysis treatment.