Removal of Zinc from Aqueous Solution by Optimized Oil Palm Empty Fruit Bunches Biochar as Low Cost Adsorbent

Table 1

Level of different factors.

Variables	Units	(−1) level	(+1) level	−alpha	+alpha
() HTT	(°C)	460.8095	639.1905	400	700
() HR	(°C/min)	7.026982	12.97302	5	15
() RT	(min)	60.40473	149.5953	30	180