%0 Journal Article
%T Equilibrium Isotherm Studies of Adsorption of Pigments Extracted from Kuduk-kuduk (Melastoma malabathricum L.) Pulp onto TiO2 Nanoparticles
%A N. T. R. N. Kumara
%A Nurulhayah Hamdan
%A Mohammad Iskandar Petra
%A Kushan U. Tennakoon
%A Piyasiri Ekanayake
%J Journal of Chemistry
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/468975
%X The adsorption of natural pigments onto TiO2 nanoparticles was investigated. The pigments were extracted from the dark purple colored pulp of the berry-like capsule of Kuduk-kuduk (Melastoma malabathricum L.). The Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models were used to analyze the equilibrium experimental data. Data correlated well with the Sips isotherm model, where the heterogeneity factor ( ) indicated heterogeneous adsorption characteristics, with a maximum adsorption capacity of 0.0130£¿mg/g. The heterogeneous adsorption character was further supported by results obtained from zeta-potential measurements. When a dye-sensitized solar cell (DSSC) was sensitized with the extracted pigment, the photo-energy conversion efficiency was measured to be 0.83%, thus proving the suitability of Kuduk-kuduk fruit pulp as a sensitizer in DSSCs. 1. Introduction Commercially, the quality of a product depends on the product value and acceptability. However, consumers are also attracted to the physical appearances of the product, especially to its colors. In food, beverages, and textile industries, the pigments are employed as coloring agents and for dyeing purposes. Natural colorants extracted from plants have been used for centuries before the first synthetic colorant was introduced. Low cost and ease of application have driven the drift from natural colorants to synthetic. However, due to environmental and health concerns associated with the applications of synthetic colorants the interest of using natural and organic sources as colorants has increased lately. Anthocyanins are natural, water-soluble, and nontoxic pigments which are responsible for the red, orange, pink, blue, or purple color of plants. The resultant color variation depends on the relative pH of the respective plant [1]. The anthocyanin pigments are expressed as red or pink under acidic media, purple in neutral media, and blue, green, or yellow in alkaline media. It turns colorless under extreme alkaline conditions [2]. Thus, anthocyanins also can be used as a pH indicator. Anthocyanins have been employed as additives or colorants in the food industry with limited usage due to its instability with varying pH levels [1]. In the alternative energy sector, natural dye extracts containing anthocyanins are integrated as sensitizers in dye-sensitized solar cells (DSSCs) because of their ability to absorb light [3, 4] and low cost associated with extraction procedures. Many researches had been conducted on analyzing the potential anthocyanins sensitizers extracted from natural
%U http://www.hindawi.com/journals/jchem/2014/468975/