Research Article
Phosphate and Nitrate Removal from Coffee Processing Wastewater Using a Photoelectrochemical Oxidation Process
Table 2
Experimental statistical design [
22,
23].
| | Factor | Name | Units | Type | Minimum | Maximum | Coded low | Coded high | Mean | Std. dev. |
| | A | pH | | Numeric | 5.00 | 9.00 | -1 ↔ 5.00 | +1 ↔ 9.00 | 7.13 | 1.57 | | B | Time | min | Numeric | 20.00 | 50.00 | -1 ↔ 30.00 | +1 ↔ 50.00 | 40.00 | 10.50 | | C | Current | amp | Numeric | 0.2000 | 0.6000 | -1 ↔ 0.30 | +1 ↔ 0.50 | 0.4033 | 0.0928 | | D | Electrolyte | g | Numeric | 0.5000 | 2.50 | -1 ↔ 1.00 | +1 ↔ 2.00 | 1.50 | 0.4549 |
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Note: the arrow “↔” represents the range between lower and higher values.
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