Dataset: pb2_walnut.csv Source: S. Saadat and A. Karimi-Jashni (2011). "Optimization of Pb(II) Adsorption onto Modified Walnut Shells Using Factorial Design and Simplex Methodologies," Chemical Engineering Journal, Vol. 173, pp. 743-749. Description/Variables 2^4 Factorial Experiment relating percent removal of Pb(II) ions from solution to 4 factors: pH(-1 = 2, +1 =10), walnut shell adsorbent dose (-1=1, +1=20), Initial metal concentration (-1=10, +1=90) Temperature (-1=15, +1=45). Variables Treatment condition (trt) pH (pH) walnut shell adsorbent dose in g/L (adsorb_dose) Initial metal concentration in mg/L (metal_conc) Temperature in Celsius (temp) Percent Pb(II) Removal (pb2_remove)