Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed‐bed column experiments

Abstract

This paper evaluates the potential use of a locally available organic soil amendment as a low-cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed-bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo-second-order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow-rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate-controlled pore diffusion was successfully performed. The adsorption process was reversed, regenerating the columns by eluting the cadmium using 0.1 mol dm −3 hydrochloric acid. The high retention capacity together with the favourable structural characteristics indicated that this material could be used as an effective and low-cost adsorbent for treatment of wastewaters containing heavy metals.  2006 Society of Chemical IndustryKeywords: cadmium; adsorption; fixed-bed column; Freundlich isotherm; kinetics; peat; intraparticle diffusivity INTRODUCTIONRemoval of heavy metals from aqueous wastes is a challenging task for the appropriate management of wastes. Heavy metals and other metal ions exist as contaminants in the wastewaters of many industries, such as tanning, mining and metal processing. Some metals associated with such activities are Pb, Hg, Cr and Cd. These metals are accumulated in living organisms and produce diseases and disorders.

Removal of cadmium from aqueous solutions by adsorption on granular red mud (GRM)

“…The statistical data have shown a fair goodness of correlation for pseudo-second-order kinetics (Fig. 5), which were reported previously for heavy metal adsorption by other low-cost adsorbents, such as peat and zeolite for the indication for a potential application in column water treatment [6,16]. After the application of the pseudo-second-order kinetics model, the results were listed in Table 4.…”

“…5. As shown from the plot, the major percent of cadmium adsorption process was completed in 8 h as for the different initial concentrations of GRM-cadmium system, which indicate itself a relatively moderate rate to reach adsorption equilibrium [6]. Fig.…”

“…However, cadmium is very difficult to remove because conventional methods employed for heavy metal removal such as chemical precipitation are either too expensive or unsuitable when confronted with the large discharge volume, low concentration waste water runoff [3].In this way adsorption method stand out for its effectiveness to remove cadmium even at low concentrations over a wide range of pH values [4]. Until now, many researches about cadmium adsorption have been conducted and the interest tends to be focused upon the use of low-cost, effective sorbents [5,6]. * Corresponding author.…”

Identification of potential soil adsorbent for the removal of hazardous metals from aqueous phase

“…Among the above-mentioned processes, adsorption plays a pivotal role in removing metals from the aqueous phase using various biomaterial sorbents, algae (Holan et al 1993), fungi, sugar cane bagasse (Cerino Córdova et al 2011;Peterlene et al 1999), rice husk, wheat barn (Nouri et al 2007), pine bark, olive cake (Doyurum and Celik 2006), coconut husk, chitin (Benguella and Benaissa 2002), ash, activated carbon (Jusoh et al 2007;Onundi et al 2011;Zavvar Mousavi and Seyedi 2011), etc. Clays, zeolite, calcite, manganese nodule residue (Agrawal and Sahu 2006;Tashauoei et al 2010), perlite (Hasan et al 2006) and peat (Gabaldon et al 2006) have also been employed to remove metals from the water phase. Also, low-cost natural clay/soil is used to develop highthroughput inorganic adsorbent as well as membrane filter in removing heavy metals from aqueous phase.…”

Sorption of copper by a highly mineralized peat in batch and packed‐bed systems

“…Several studies have also demonstrated removal capacities in column systems that are different from those predicted from batch equilibrium isotherms. 2,17,31,32 The discrepancies among batch and dynamic sorption data can be attributed to the type of metal-sorbent contact in column experiments, in which the sorbent-to-solution ratio is much higher than in batch mode and the feed solution is continuously pumped, so solutes present in the column are continuously replaced and, at equilibrium, concentration is equal to its respective feed value.…”