Fe(III) ion cross-linked alginate-carboxymethyl cellulose composite beads (Fe@(Alg-CMC)) were prepared and used as a novel photocatalyst for the degradation of malachite green (MG) dye. Fe (III) ions bound to the carboxyl groups of the biopolymer composite provided reactive radicals under UV light, and degradation of the dye in an aqueous solution occurred at a high percentage and in a short time. Unlike Fenton's reaction, effective degradation of the dye was carried out without adding H2O2 to the medium. Optimum conditions of dye degradation were investigated. Under UV-A light, 98.8%+/- 0.7% dye degradation was achieved at pH 4 of 10 ppm MG solution with 0.1 g of Fe@(Alg-CMC) beads in 30 min. Experimental results fitted Langmuir-Hinshelwood kinetic modeling, which explains the kinetics of the heterogeneous catalytic processes. A rate constant (k) of 0.115 +/- 0.001 min(-1) and correlation coefficient (R2) of 0.9628 was obtained. Hereby, we offer Fe@(Alg-CMC) beads as a promising, environmentally friendly, easy to prepare, and low-cost catalyst for the degradation of dyes and organic substances under UV light.