Chemical Modifications of Cassava Peel as Adsorbent Material for Metals Ions from Wastewater

Table 5

Multiple quadratic mathematical equations obtained from the response surfaces for adsorption of Cd(II), Pb(II), and Cr(III) by adsorbents based on cassava peels, chemically modified and in natura.

	Adsorbents	Equations
Cd	M. in natura	= 2.31392 − 0.00389216 + 0.00000183 + 0.0994207 − 0.00765268 − 0.00002575	0.970
	M. H2O2	= 2.22661 − 0.00391300 + 0.00000179 + 0.1135094 − 0.010198 − 0.0000021231	0.979
	M. H2SO4	= 2.09311 − 0.00367333 + 0.00000169 + 0.117596 − 0.0099065 − 0.00001022567	0.969
	M. NaOH	= 2.49556 − 0.00426238 + 0.00000195 + 0.106341 − 0.01022994 − 0.00000413033	0.969
Pb	M. in natura	= 2.42402 − 0.00410920 + 0.00000188 + 0.091384 − 0.00873871 − 0.00000392186	0.973
	M. H2O2	= 2.40349 − 0.00408627 + 0.00000186 + 0.090141 − 0.0092527 + 0.0000022304	0.975
	M. H2SO4	= 2.20750 − 0.00386993 + 0.00000182 + 0.108006 − 0.008937 − 0.0000172072	0.969
	M. NaOH	= 2.44355 − 0.00408057 + 0.00000187 + 0.0706209 − 0.006958 − 0.0000014771	0.974
Cr	M. in natura	= 2.60020 − 0.00422655 + 0.00000173 + 0.04990993 − 0.015409 + 0.00008415263	0.964
	M. H2O2	= 2.49313 − 0.00414079 + 0.00000176 + 0.08114590 − 0.015967 + 0.00005636427	0.965
	M. H2SO4	= 2.46274 − 0.00418541 + 0.00000178 + 0.10776064 − 0.0177875 + 0.0000522846	0.977
	M. NaOH	= 2.92410 − 0.00392245 + 0.00000163 − 0.149982207 + 0.005562 + 0.00006738493	0.986

= adsorbent mass (mg); = pH of the contaminant solution; = adsorbed quantity (mg g⁻¹).