Hexavalent chromium removal from aqueous solutions by using low-cost biological wastes: equilibrium and kinetic studies

Sesame leaf and stem, as a kind of useless agricultural waste, was used as a sort of low-cost biosorbent for the removal of cadmium ions from aqueous solutions in batch and continuous modes. The biomass was characterized by Fourier transform infrared spectroscopy, scanning electron microscope and energy-dispersive X-ray analysis before and after adsorption. There were hydroxyl group, carboxyl group, etc. on the surface of the adsorbent from Fourier transform infrared spectroscopy. A batch study was employed as a function of the initial concentration, adsorbent particle size, adsorbent dose, contact time and the pH of the solution. Maximum sorption was found to occur at an initial pH of 6. The equilibrium process was satisfactorily described by the Langmuir isotherm model with the maximum sorption capacity of 84.74 mg g -1 . Kinetic studies also indicated that both pseudo-first-order and pseudo-second-order kinetic models (with R 2 values of 0.9929 and 0.9952, respectively) were able to describe the process. A continuous study was carried out, and the maximum uptake of cadmium ions in a fixed-bed adsorption column was found to be 22.88 mg g -1 , where the initial concentration of cadmium ions, bed height, flow rate and pH were 60 mg L -1 , 2 cm, 2.5 mL min -1 and 5.5, respectively.

Section: Introductionmentioning

confidence: 99%

Adsorption of cadmium ions from aqueous solutions using sesame as a low-cost biosorbent: kinetics and equilibrium studies

Cheraghi

Ameri

Moheb

2015

“…However, these techniques have certain disadvantages such as incomplete removal, complicated treatment process, high cost, high energy requirement and operational cost, use of chemicals, and generation of toxic sludge or other waste products that again require disposal (Dubey and Shiwani 2012;Aliabadi et al 2012;Kumar et al 2012). Adsorption processes using natural adsorbents or agricultural waste products are becoming the new alternatives for the removal of fluoride from aqueous solution as they are cheap, simple, sludge-free, regenerable, environment friendly, involve small initial cost, and minimal chemical use (Saka et al 2012;Zhu et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Defluoridation of water by activated carbon prepared from banana (Musa paradisiaca) peel and coffee (Coffea arabica) husk

Tilahun

Hussen

Rao

2014

109

The defluoridation of ground water is regarded as one of the key areas of attention among the universal water community. The present investigation deals with fluoride removal from aqueous solution by thermally activated biosorbents prepared from banana (Musa paradisiaca) peel and coffee (Coffea arabica) husk. Fluoride ion selective electrode was used for the determination and monitoring of fluoride ion concentration. Batch experiments were conducted to establish the optimal conditions like pH, dose of the adsorbent, and contact time. The optimum pH was found to be 2 for both the adsorbents, and the optimum dose was found to be 24 g/ 250 mL at 13 h contact time for banana peel and 18 g/250 mL at 3 h contact time for coffee husk. The concentrations determined in real water samples of flour factory, poultry, and Lake Hawassa sites were 12.54, 11.02, and 6.72 mg/L, respectively. The prepared biosorbents were applied on these water samples under optimized conditions and found to be effective with removal efficiency ranging from 80 to 84 %. In terms of time and adsorbent dose required, coffee husk was observed to be much better than banana peel. The adsorption process obeyed Langmuir adsorption model. From the kinetic perspective, the fluoride adsorption followed the pseudo second-order reaction kinetics.

“…The equation for the pseudo-first-order kinetic model can be expressed as below (Aliabadi et al 2012):…”

Section: Pseudo-first-order Kinetics Modelmentioning

confidence: 99%

“…The pseudo-second-order kinetic model (Ho and McKay 1999;Aliabadi et al 2012) is described by the following equation:…”

Section: Pseudo-second-order Kinetics Modelmentioning

confidence: 99%

Nitrate removal using Purolite A520E ion exchange resin: batch and fixed-bed column adsorption modelling

Nur

Shim

Loganathan

et al. 2014

Removing excessive nitrate from water is essential because it causes eutrophication which in turn has a harmful effect on aquatic life, resulting in a reduction in biodiversity and posing a danger to people's health when the water is used for drinking. In this study, nitrate removal from aqueous solutions was studied using an ion exchange resin (Purolite A520E) in batch and fixed-bed column experiments. Batch adsorption kinetics was very well described by pseudo-first-order, pseudo-second-order and homogeneous surface diffusion models for resin doses 1.5 and 3.0 g/L at a nitrate concentration 20 mg N/L. Column kinetic data satisfactorily fitted to the empirical Thomas model and a numerical model based on advectiondispersion equation for filtration velocities 2.5 and 5.0 m/h at a column height of 12 cm and inlet concentration 20 mg N/L. The experimental and Thomas model predicted breakthrough adsorption capacity ranges for the two filtration rates were 12.0-13.5 and 8.2-9.7 mg N/g, respectively, whereas the maximum adsorption capacity determined using Langmuir adsorption isotherm model in the batch study was 32.2 mg N/g.