The Influence of Lead Concentration on Photocatalytic Reduction of Pb(II) Ions Assisted by Cu-TiO₂ Nanotubes

Table 1

The maximum contaminant level (MCL) standard for the most hazardous heavy metal [4].

Heavy metal	Toxicities	MCL (ppm)
As	Skin manifestations, visceral cancers, vascular disease	0.050
Cd	Kidney damage, renal disorder, human carcinogen	0.01
Cr	Headache, diarrhea, nausea, vomiting, carcinogenic	0.05
Cu	Liver damage, Wilson disease, insomnia	0.25
Ni	Dermatitis nausea, chronic asthma, coughing, human carcinogen	0.20
Zn	Depression, lethargy, neurological signs, and increased thirst	0.80
Pb	Damage the fetal brain, diseases of kidney, circulatory system, and nervous system	0.005
Hg	Rheumatoid arthritis and diseases of kidneys, circulatory and nervous system.	0.00003