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.
To obtain information that can be used as reference for improving the environment inside and surrounding the open channels receiving johkasou effluent, the formation and correlation of sediment bed bacterial density with water quality were evaluated with multivariate statistical analysis based on measured data for water and sediment samples collected for 8 times from 6 sites of an open channel that receives johkasou effluent in a residential area of Gifu Prefecture, Japan. Statistical analysis included principal component and factor analysis (PCA/FA), cluster analysis (CA) and correlation analysis. The PCA/FA results showed that 3 dominant factors were responsible for the water quality data structure, accounting for 85.12% of the total variance in the dataset. Hierarchical cluster analysis grouped 6 study sites into 3 statistically significant clusters, reflecting different characteristics and pollution levels of the sites. Correlation analysis revealed statistically significant relationships of the sediment bed bacterial density with BOD, total nitrogen and total phosphorus in the water of the channel receiving johkasou effluent.
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.
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