Fitting parameters of the Langmuir and Freundlich equations for Cu(ii), Zn(ii) and Pb(ii) adsorption onto the prepared adsorbent PEI-RCSA in single system.

Isotherm model		Metal ion
		Cu(ii)	Zn(ii)	Pb(ii)
Experimental	q m,exp (mg g−1)	172.5	106.9	229.1
Langmuir	q m,cal (mg g−1)	177.1	110.2	234.2
	K L (L mg−1)	0.0355	0.0323	0.0442
	R 2	0.9992	0.9993	0.9993
	R L	0.0274–0.2731	0.0301–0.2925	0.0221–0.2317
Freundlich	K F	43.8595	32.6922	54.7670
	n	4.5910	5.4015	4.3018
	R 2	0.9340	0.9261	0.9412