Removal of phosphorus from aqueous solution using lignite fly ash

183-187Phosphorus (P) is an important element in making a major contribution to agriculture and industrial development. However, its release to surface waters leads to serious pollution. The development of technology for P removal offers the opportunity for abatement of environmental hazards and recycling. Fly ash is widely available and a cheap adsorbent and its alkaline properties make it interesting for use in waste water treatment through precipitation of phosphates. An attempt was made to study the P removal ability of lignite fly ash from Neyveli Lignite Corporation (Tamil Nadu). In order to determine the phosphate removal capacity of fly ash and the effect of adsorbent quantity (5 and 10g per 100mL), temperature (28 and 50°C), retention time (5 and 30 min) on P removal, sorption studies were conducted using phosphate solutions containing 20, 50, 100, 150 and 200 mg/L P. The results showed that the LFA was able to remove even 100% of 20 mg/L at 10g adsorbent with 30 min retention time at 28°C. The P removal capacity decreased with increase in P concentration, the removal was 86.51% at 200 mg/L P. The adsorbent quantity significantly influenced the P removal; the average removal was 94.81% at 5g and 97.5% at 10g. The data was also fitted into Langmuir and Freundlich adsorption equation. The Langmuir adsorption maximum was the highest for 5g fly ash-30 min equilibrium at 28°C (40.98 mg/kg). The adsorption maxima decreased with increase in temperature, however, the factor related to bonding energy has increased at 50°C. Altogether the study revealed that the LFA could be successfully used for instantaneous P removal at ambient condition, however other parameters like solid-liquid ratio, maximum carrying capacity, etc. need to be yet optimized