This work describes the potential of utilizing prepared activated carbon from apricot stones as an efficient adsorbent material for tartrazine (TZ) azo-dye removal in a batch and dynamic adsorption system. The results revealed that activated carbons with well-developed surface area (774 m 2 /g) and pore volume (1.26 cm 3 /g) can be manufactured from apricot stones by H 3 PO 4 activation. In batch experiments, effects of the parameters such as initial dye concentration and temperature on the removal of the dye were studied. Equilibrium was achieved in 120 min. Adsorption capacity was found to be dependent on the initial concentration of dye solution, and maximum adsorption was found to be 76 mg/g at 100 mg/L of TZ. The adsorption capacity at equilibrium (q e) increased from 22.6 to 76 mg/g with an increase in the initial dye concentrations from 25 to 100 mg/L. The thermodynamic parameters such as change in free energy (DG 0), enthalpy (DH 0) and entropy (DS 0) were determined and the positive value of (DH) 78.1 (K J mol-1) revealed that adsorption efficiency increased with an increase in the process temperature. In fixed-bed column experiments, the effect of selected operating parameters such as bed depth, flow rate and initial dye concentration on the adsorption capacity was evaluated. Increase in bed height of adsorption columns leads to an extension of breakthrough point as well as the exhaustion time of adsorbent. However, the maximum adsorption capacities decrease with increases of flow rate. The breakthrough data fitted well to bed depth service time and Thomas models with high coefficient of determination, R 2 C 94.

Decolourisation of wastewater, particularly from textile industries, is one of the major environmental concerns these days. Current methods for removing dyes from wastewater are costly and cannot effectively be used to treat wide range of such wastewater. This work describes the use of commercially available granular activated carbon (GAC) as an efficient adsorbent material for dyes' removal. Aqueous solutions of various concentrations of the basic dye Methylene Blue (MB) and the azo-dye Tartrazine at 5-20 mg.L -1 and 10-100 mg.L -1 , respectively, were shaken with certain amount of GAC to determine the adsorption capacity and removal efficiencies. The effects of adsorbent dose, initial pH, initial dye concentration, agitation speed, and contact time on dyes' removal efficiencies have been studied. Maximum dye concentration was removed from the solution within 60-90 min. after the beginning of every experiment. Adsorption parameters were found to fit well into Langmuir and Freundlich adsorption isotherm models with correlation coefficient (R 2 > 0.99) in the concentration range of MB and TZ studied.

The removal of dyes from colored effluents, particularly from textile industries, is one of the major environmental concerns these days. Current methods for removing dyes from wastewaters are costly and cannot effectively be used to treat wide range of such wastewaters. This work describes the use of commercial available activated carbon as an efficient adsorbent material for dye removal. Aqueous solutions of various basic dye Methylene Blue (MB) and azo-dye Tartrazine (TZ) concentrations 5-20 mg l -1 and 10-100 mg l -1 , respectively, were shaken with certain amount of adsorbents to determine the adsorption capacity. The effects of adsorbents dose, initial pH, initial dye concentration, agitation speed and contact time on dye removal have been studied. Maximum dye was removed from the solution within 60-90 min after the beginning of every experiment. Adsorption parameters were found to fit well into Langmuir and Freundlich adsorption isotherm models with correlation coefficient (R 2 > 0.99) in the concentration range of MB and TZ studied.

The kinetic and mechanistic study of the removal rate of tartarzine by adsorption onto activated carbon under the influence of shaking speed is presented in this work. Diffusion binding model (DB-model) and pseudo second order model (PSO-model) were applied for suggesting the dependency of surface-reaction (solute or active site) and to give the main outputs; adsorption rate constants and capacities. According to error evaluation of both models, it was found that DB-model is more representative for tartarzine activated carbon adsorption system than PSO-model and it is suggested that surface-reaction kinetic is dependent on tartrazine concentration not on active sites of adsorbent. In addition, DB-model showed that adsorption rate constants and capacities increase with shaking speed which agrees with the fact of enhancing some diffusion steps because of shaking. DB-model, as a diffusion model as well, was applied to investigate diffusion mechanistic and it was concluded that for static condition (shaking speed = 0 rpm), adsorption passes two stages, the first is controlled by bulk-diffusion and film-diffusion and the second is controlled by intraparticle-diffusion. For shaking speeds 25 rpm and 50 rpm, bulk-diffusion and filmdiffusion almost have no contribution in controlling overall rate and consequently intraparticle-diffusion is the controlling step. For shaking speeds from 75 to 125 rpm, intraparticle-diffusion is suggested to have strong contribution in controlling adsorption process.