Parameters Unit Range and levels (coded) -α -1 0 +1 +α pH   2.9 4.0 5.5 7.0 8.0 Adsorbent Dose g L-1 3.3 5.0 7.5 10 11.7 Time mins 27.44 30 33.75 37.5 40.06

Table 1: Experimental range and levels of independent parameters for RSM study.