To make the adsorption process more economic and environmental friendly, it is necessary to study desorption and reutilization of the adsorbents. In the present study, the effectiveness of natural pumice in removal of iron from aqueous solution was investigated in several sorption-desorption cycles. The desorption characteristics of previously adsorbed iron ions on natural pumice were tested by various desorbing agents such as HCl, NaOH and aquadest. Among them, HCl showed the highest desorption efficiency (37.89%) with 0.1 M of concentration and 60 min of contact time. The removal efficiency of iron ions in reused natural pumice could be maintained up to 90% in the third cycle of adsorption. The results indicate that although complete desorption was not achieved, natural pumice from Sungai Pasak, West Sumatra, Indonesia, can be sufficiently reused up to three cycles of adsorption-desorption.
Adsorption of iron from aqueous solution by using maize husk (Zea mays L.) as a low-cost adsorbent was studied. Batch experiments were carried out at ambient temperature, 0.075-0.250 mm of particle size and 100 rpm of agitation speed to determine the influence of initial pH, adsorbent dose, initial concentration and contact time on the removal of iron. Langmuir and Freundlich models were applied to describe the adsorption isotherm of iron by maize husk. The results showed that optimum condition of iron removal were 4 of pH solution, 20 g/L of adsorbent dose, 10 mg/L of Fe concentration and 15 min of contact time of adsorption with 0.499 mg Fe/g maize husk of adsorption capacity. Experimental data fitted well to Langmuir's adsorption equilibrium isotherm within the concentration range studied. This study demonstrated that maize husk, which is an agricultural waste, has potential for iron removal from groundwater or other polluted waters.
This study aims are toanalyze the spatial variation of electrical conductivity (EC) values, total suspended solids (TSS), and total dissolved solids (TDS) concentrations along the Batang Arau River. Water samples were collected from eight stations along the river at biweekly intervalsbetween March and May 2014. The results indicate an increasing trend in the value of three parameters from upstream to downstream, reflecting the effect of natural and anthropogenic activities along the river. The EC values were in the range of 173-5,097 μS/cm and had exceeded the water quality standard established by World Health Organisation (WHO) at the downstream. The TSS and TDS concentrations were in the range of 76-2,078 mg/L and 124-3,560 mg/L, respectively. The TSS concentrations at all stations had exceeded the river quality standard of class II established by Governor Regulation of West Sumatera, while the TDS concentrations had exceeded only at the downstream area. Significant spatial variation of the EC and TDS concentrations was observed between the upstream-midstream and the downstream but was not obtained along the river for the TSS concentrations. It indicates that the anthropogenic activities along the river affected the variability of EC and TDS, but not for TSS. Based on these results, reducing the number of sampling points into three stations could be performed for the EC and TDS, while TSS monitoring at only one station could be applied.
To investigate the potential of adsorption and regeneration of natural pumice from West Sumatera Indonesia for total chromium (Cr) removal from aqueous solution, batch experiments in multiple adsorption-desorption cycles were performed. The results indicated that the optimum condition of total Cr removal were 3 of pH solution, 0.3 g/L of adsorbent dose, 60 min of contact time of adsorption, <63 ?m of diameter of adsorbent, and 1 mg/L of total Cr initial concentration with 2.226 mg Cr/g pumice of total Cr uptake. The experimental data obtained were fitted with the Freundlich adsorption isotherm within the concentration range studied. Desorption efficiencies for total Cr ions by using 0.1 M HCl as desorbing agent were in the range of 31-32%. Although complete desorption were not attained, the natural pumice could be sufficiently reused up to 3 cycles of adsorption- desorption with increasing trend in total Cr uptake that may due to the surface modification of natural pumice caused by HCl. Overall results revealed that easy availability of natural pumice as local mineral in West Sumatra, Indonesia and its ability to adsorb and retain total Cr will create more interest to develop new natural adsorption method of pollutant removal from solution.
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