Numerical modelling and laboratory studies on the removal of Direct Red 23 and Direct Red 80 dyes from textile effluents using orange peel, a low-cost adsorbent

Wastewater containing direct dyes discharged from various industries, in particular, textile industry often causes many environmental problems. Considering the possibility of the adsorption process of synthetic dyes and their removal from aqueous solutions using orange peel as an eco-friendly and low-cost adsorbent before discharging to the receiving environment is the most important task. This paper presents a numerical finite element model to simulate the removal of dissolved textile synthetic dyes from wastewater taking into consideration both linear and the Langmuir isotherms to describe adsorption process. The CTRN/W model was integrated with SEEP/W model and modified to solve mathematical equations describing the problem at hand. The modelling accuracy was first verified with an analytical equation for a reactive mass transport problem including advection, dispersion and linear adsorption processes through groundwater flow medium. The modelling results were then compared to those results obtained from experimental tests for the removal of Direct Red 23 and Direct Red 80 dyes from textile wastewater using orange peel adsorbent. The model predictions somewhat agree with the experimental measurements. It was found that the adsorption process by orange peel adsorbent could be well described by the Langmuir isotherm. Furthermore, a pseudo-second order kinetics showed to be well-suited with the rate of sorption. Although the generation of such wastewater by the different industries is nearly unavoidable, the results of model presented here can help to design an appropriate environmental management strategy to minimise the adverse impacts caused by industrial wastewater. (c) 2005 Elsevier Ltd. All rights reserved.