This　study　focused　on　the　competitive　biosorption　of　Yellow　2G　(Y2G)　and　Reactive　Brilliant　Red　K-2G　(RBR)　by　inactive　aerobic　granules　in　binary　solutions.　A　first-order　derivative　spectrophotometric　method　for　the　simultaneous　determination　of　Y2G　and　RBR　in　binary　solutions　was　developed.　Dubinin-Raduskevich　(D-R)　isotherm　successfully　predicted　the　biosorption　of　Y2G　and　RBR　in　both　single　and　binary　solutions.　However,　none　of　the　tested　binary　adsorption　isotherms　could　realistically　represent　the　biosorption　equilibrium　data.　Maximum　biosorption　capacity　calculated　from　D-R　isotherm　for　Y2G　and　RBR　in　single　solution　was　58.50　and　66.18　mg　g(-1),　respectively;　in　binary　solutions,　for　Y2G　it　decreased　to　40.38　mg　g(-1),but　for　RBR　it　increased　to　171.21　mg　g(-1),　their　synergism　and　antagonistic　interactions.　The　FTIR　results　indicated　the　main　functional　groups　on　aerobic　granules　for　biosorption　of　Y2G　and　RBR　would　be　amine,　hydroxyl,　carboxyl　and　either.　(C)　2010　Elsevier　Ltd.　All　rights　reserved.