Modeling the Sorption of Ni²⁺ and Co²⁺ on Saprist Peat Using the Response Surface Methodology

Table 4

Corrected predicted and actual % metals retained after 18 h contact/shaking time.

	Metal conc. (mg/L)	Peat dose (g/L)	Predicted	Actual	Predicted	Actual	Predicted	Actual	Predicted	Actual
			pH 3		pH 6		pH 8		pH 10
Ni^2+	50	5	82.4	66.9	102.9^*	86.5	86.6	72.4	48.2	32.6
	50	10	86.7	74.5	103.4^*	91.0	85.9	76.0	45.5	40.0
	50	15	90.2	83.7	103.7^*	96.4	84.2	77.1	41.8	40.5
	50	20	92.3	91.5	103.0^*	98.5	81.5	78.0	37.1	44.0
	100	5	68.7	56.2	88.3	73.5	72.8	57.2	34.5	22.0
	100	10	71.2	62.5	87.9	84.0	70.4	64.7	30.0	32.4
	100	15	72.7	64.0	86.4	88.2	66.9	69.5	24.5	34.3
	100	20	73.3	76.2	83.9	97.5	62.4	72.8	18.0	33.5
	150	5	54.9	42.5	74.6	58.6	59.1	49.0	20.7	15.9
	150	10	55.7	57.3	72.3	71.5	54.8	62.0	14.5	18.6
	150	15	55.5	72.5	69.1	83.8	49.6	66.1	07.2	21.1
	150	20	54.2	80.0	64.9	91.6	43.4	68.0	−1.0^**	22.8
Co^2+	50	5	46.5	46.0	47.8	50.0	53.3	54.0	62.4	62.6
	50	10	61.3	62.5	61.8	61.5	66.8	69.0	75.4	74.8
	50	15	73.5	73.1	73.3	76.0	77.8	80.1	85.9	91.0
	50	20	83.3	80.5	82.3	83.0	86.3	86.4	93.9	94.0
	100	5	39.5	40.2	42.3	43.2	48.7	57.2	58.8	60.0
	100	10	54.3	56.5	56.3	54.0	62.2	61.7	71.8	72.5
	100	15	66.5	67.3	67.8	58.0	73.2	71.5	82.3	80.8
	100	20	76.3	76.2	76.8	74.0	81.7	82.0	90.3	96.5
	150	5	34.2	42.5	38.4	38.5	45.8	47.0	56.8	59.5
	150	10	48.9	57.3	52.4	53.2	59.3	60.0	69.8	68.6
	150	15	61.2	72.5	63.9	63.5	70.3	71.1	80.3	75.5
	150	20	70.9	80.0	72.9	71.5	78.8	80.0	88.3	88.0
MAPE for Ni^2+, original				0.16		0.15		0.21		0.65
MAPE for Ni^2+, corrected				0.16		0.13		0.16		0.36
MAPE for Co^2+, original				0.07		0.09		0.06		0.06
MAPE for Co^2+, corrected				0.06		0.002		0.03		0.03

The model predicted >100% Ni²⁺ uptake.
^**The model predicted negative Ni²⁺ uptake.