engleski

The influence of grain size of waste foundry sands on removal percentage of Copper ions

Foundry sand is used during the metal casting production. It consists of quartz sand (>90 %), binders (chemical or clay) and additives. Waste foundry sand (WFS) may be used in constructions and in recently for heavy metals removal from aqueous solutions by adsorption. Heavy metals, e.g. copper, may cause many diseases and for this reason they must be controlled in waste water. In this research the influence of grain size of chemical bonded (sodium-silicate) waste foundry sand (WFS-CHB) and clay bonded (bentonite) waste foundry sand (WFS-CB) on removal percentage of Cu(II)-ions was examined. Adsorption was performed with 1 g of WFS-CHB, as well as WFS-CB, and 50 ml Cu(II)-ions solution of concentration 100 mg/l at 25 C until equilibrium state (20 min). Sediments in form of discs were prepared with binder KBr for microscopic examination. Microstructure was observed by stereo microscope equipped with digital camera. Grain size was determined by Olympus GX51-Analysis software according to ASTM standard E112-96 and its effect on efficiency of adsorption was established as well. Validation of ions removal in this research was performed using light microscopy, as a part of adsorption research which is in a progress. Light micrograph of WFS-CHB shows that the mixture of binder and sand is not homogenous and that the adsorption occurred. The smallest average grains size was in sample of WFS which is clay bonded. After adsorption, diameter of grains was increased. Among the all samples the largest grains are in the sample of waste foundry sand - chemical bonded after adsorption. Sediment on the sand grains increased their average size. The percentage of Cu(II)-ions removal from solution is higher for sample of chemical bonded waste foundry sand compared to this for clay bonded sample probably due to simultaneously sedimentation and adsorption and assuming that in latter sample only adsorption is taken place. Microscopical observations in this research were proved removal potential of waste foundry sand. Since the difference in initial grains size in WFS-CHB and WFS-CB samples was measured as negligible, it is not a crucial for a good adsorption. According to grain size after bonding, Cu(II)-ions removal is better with chemical bonded than clay bonded WFS. Obtained results show that waste foundry sand is suitable for removal of Cu(II)-ions from aqueous solutions. Since there is a lack of literature data, this research will contribute to new insight of using the waste foundry sand as a quality and low-cost agent for removal of Cu(II)-ions.

Microstructure ; Grain Size ; Waste Foundry Sands ; Adsorption ; Heavy metals

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