Adsorption of Titanium Industry Effluent Contaminated with Chromium Using Bird Bone

Bird bone was used as adsorbent to remove chromium from Titanium industry effluent which was located in Trivandram. Laboratory experimental investigation was carried out to identify the binding of chromium ions by bird bone was found to be mainly influenced by pH, with maximum sorption 14.45 ± 0.98 ppm found in the effluent after adsorption at pH 7. The metal uptake by bird bone particles was maximum (13.35 ± 0.75 ppm) at room temperature and increasing temperatures decreased the Cr ion uptake.


Experimental design
The experimental was designed to analyze the adsorptive potential of cheap bioresource, capable of entrapping Cr and ion in the aquatic and semi aquatic media. The powdered adsorbents were mixed with the two different types of effluents (raw and treated effluent) in 5 different concentration of 1, 2, 3, 4 and 5 mg/l. The medium was separately maintained at six different pH levels (0. 5, 2, 4, 7, 8 and 9). The adsorbent were thoroughly mixed with the toxicant solution and the mixture was agitated once in 2 h. The initial concentrations of Cr was estimated in the two different effluents. The treatment was run for a period of more than 60 days. The Cr content of the effluents was estimated after 60 days of interaction with the adsorbents. The difference between the initial and final metal levels indicated the quantity adsorbed by the bioresource used.
The effect of temperature on the adsorptive potential of the materials used was estimated at pH 7. For assessing the effect of temperature, the reaction mixtures were allowed to interact in a 250 ml Erhlen-Meyer flask. The flasks were placed inside separate incubators maintained at 42, 32 and 28°C. The experiments were continued for more than 60 days and the quantities of Cr was analysed in the treated effluent.

Estimation of heavy metal (Cr)
An Atomic Absorption Spectrophotometer (ELICO) model with Air-C2H2 flame type,with an average fuel flow rate between 0.8-4.0 L min-1 and the support gas flow rate between 13.5-17.5 L min-1 was used for sample analysis and operated as per the equipment manual .The single element hollow cathode lamps for respective metals were of ELICO Co.Ltd-L series. Calibration curves for various elements obtained from these standards were of first order reaction. The sample for Cr analysis was aspirated with the help of an Automatic sampler.

Results and Discussion
Maximum amount of bird bone powder adsorbed chromium at pH 7 and at 5g of adsorbent used, 14.45 ± 0.98 ppm of chromium found in the raw titanium industry effluent (after sludge off). At pH 0.5, at 5 g bird bone powder, 39.66 ± 0.53 ppm of chromium was found in the effluent (Table 1).
Similarly in the case of Table 2, maximum adsorption of Cr found at pH 7 and 10.00 ± 0.89 ppm of Cr has left in the effluent after adsorption by the bird bone powder at the dosage of 5 g/l and 41.94 ± 0.82 ppm of Cr found in the effluent after adsorption at pH 0.5 at the dosage of 1 g/l.
The highest amount of chromium was adsorbed at the adsorbent concentration of 5 g/l temperature of 28°C and the concentration of chromium left in the effluent after adsorption was 20.28 ± 0.70, 18.41 ± 0.42, 15.78 ± 0.85, 14.32 ± 0.86 and 13.35 ± 0.75 ppm at the adsorbent concentration of 1,2,3,4 and 5 g/l ( Table 2). The lowest amount of Cr adsorption occurred when temperature (42°C) was high (Table 3).
Highest adsorption was recorded at temperature (28°C) at the adsorbent dosage of 5 g/l as 8.83 ± 0.45 ppm (amount of Cr left in the effluent after adsorption) and lowest adsorption recorded at 42°C at the dosage of 1 g/l as 41.04 ± 0.38 ppm (amount of Cr left in the effluent after adsorption) Table 4.
Bird bone powder effectively adsorbed chromium from the titanium industry effluent. Higher dosages of the adsorbent removed more quantities of Cr compared to low dosages, indicating an additive effect. But the effectiveness of the adsorbent is more when administered in lower dosages. At pH 7, 1 g bird bone powder removed about 22.33 ppm of Cr while 5 g removed only 32.19 ppm, thus adsorption is not directly proportionate to the quantity of adsorbent used. Thus adsorption is not directly proportionate to the quantity of adsorbent used. The sites available for adsorption seemed to decrease when more quantities of the adsorbent are administered.
The pH influenced adsorption of Cr by bird bone powder. At acidic pH levels, the quantity of Cr adsorbed much less compared to neutral and alkaline pH levels. Thus pH plays a vital role in determining the quantity of Cr adsorbed from the medium by bird bone powder. The pH seemed to modify the adsorption potential of bird bone powder and the pH should be maintained at 7.0 to achieve maximum adsorption of Cr. Agarwal and Gupta [9] found out that animal bone charcoal acts as a low cost adsorbent for Cr(vi) from aqueous solution.
Zhu et al. [10] reported that fluorine removal efficiency increased from 21 to 95.80% with increase in adsorbent dose of 0 to 40 g/l of modified bone char. Olaniyi et al. [11]    Chojnacka [12] and Chen et al. [13] pointed out that cow bone charcoal is used as a microporous adsorbent, metals penetrate easily in to these pores, when the ionic size becomes small. Han et al. [14] and Jain et al. [15] pointed out that different chemical functional groups such as carboxyl, hydroxyl and amide are responsible for biosorption of metal ions. These functional groups are the potential sites for adsorption and the uptake of metal depends on various factors such as abundance of sites, their accessibility and affinity between the adsorption site and metal.
Temperature was another significant factor determining adsorption of heavy metals .At higher temperatures (42°C), even 1 g of adsorbent adsorbent removed 55.1 percent of Cr from the titanium industry effluent at the ideal pH of 7.
Ibrahim et al. [16] studied the effect of maximum metal ion concentration for the adsorption capacity of chromium and lead at 30°C and here cowbone charcoal was used as an adsorbent. Olaniyi et al. [11] found that at 30°C, cow bone reported the effect of temperature for the removal of metals using an immobilized sorbent obtained from poultry waste.