Can somebody explain why normal diode(1N4001 or 1N4007) is used in rectifier bridge insteed of schottky diode

Traditional diodes are cheaper than schottky diodes and they can usually block a higher voltage in the opposite direction. In most power rectification applications like yours schottky diodes are used to limit voltage drop and power loss.

In your case whether or not you need a schottky diode depends if you need to limit voltage drop or power loss.

The high switching speed of Schottky diodes is not especially useful in rectification. "High frequency", in this context, means frequencies measured in MHz or GHz. 50-60 Hz is a low enough frequency that a normal P-N diode will function acceptably.