Potato Peels as an Adsorbent for Heavy Metals from Aqueous Solutions: Eco-Structuring of a Green Adsorbent Operating Plackett–Burman Design

Table 3

PBD matrix for coded and uncoded variables. Response is shown as observed and predicted % of removal of Cd (II) using BPP.

Run	Coded levels of variables				Uncoded variables				Response (Y, %)
	A^a	B^b	C^c	D^d	A^a	B^b	C^c	D^d	Obs.	Pred.	Pred.
1	+1	−1	+1	−1	9	10.0	3.00	5.00	34.82	45.39	52.50
2	+1	+1	−1	+1	9	200	0.10	60.0	98.50	87.54	98.65
3	+1	+1	+1	−1	9	200	3.00	5.00	97.00	88.66	96.49
4	−1	+1	−1	−1	3	200	0.10	5.00	90.00	97.14	99.19
5	−1	−1	−1	−1	3	10.0	0.10	5.00	70.00	67.66	69.63
6	0	0	0	0	6	105	1.55	32.5	95.65	85.65	86.60
7	+1	−1	+1	+1	9	10.0	3.00	60.0	40.00	41.06	42.57
8	−1	−1	+1	+1	3	10.0	3.00	60.0	40.00	46.32	42.57
9	+1	+1	−1	+1	9	200	0.10	60.0	98.40	100.0	98.65
10	−1	+1	+1	+1	3	200	3.00	60.0	96.14	85.59	95.89
11	−1	+1	+1	−1	3	200	3.00	5.00	97.00	93.93	96.49
12	−1	−1	−1	+1	3	10.0	0.10	60.0	74.30	63.32	67.28
13	+1	−1	−1	−1	9	10.0	0.10	5.00	71.43	62.39	69.64

A^a is the pH of the solution, B^b is the heavy metal concentration (HMC, ppm), C^c is the adsorbent dose (AD, g/L), and D^d is the contact time between adsorbent and HM solution (CT, min). Obs.: experimental values; Pred.: predicted values before response transformation: Y = 68.99 − 0.877 pH + 0.2277 HMC − 5.86 AD − 0.0789 CT + 9.66 Ct Pt; Pred.: predicted values after response transformation: .