Removal of Hexavalent Chromium from Aqueous Solutions Using Natural Zeolite Coated with Magnetic Nanoparticles: Optimization, Kinetics, and Equilibrium Studies

Table 1

Maximum discharge limits of some heavy metals in water and wastewater (mg/L).

Heavy metal	Maximum contaminant limit (mg/L)
	Water	Wastewater
Chromium	0.05	0.10
Mercury	0.001	0.00003
Arsenic	0.02	0.05
Cadmium	0.005	0.01
Lead	0.01	0.006
Nickel	0.02	0.20
Zinc	5.0	0.80
Copper	1.0	0.025