Many articles claim that coriander juice (a.k.a. cilantro) has chelation properties and help in excrement of toxic metals.
For example: Raw Food Hypocrite:
A recent study by Dr. Yoshiaki Omura from the Heart Disease Research Foundation, New York, has discovered that the herb cilantro will detoxify mercury from neural tissue*., is used to help stimulate the appetite and relieves minor digestive irritation.
Is this scientifically validated?
There is no limited evidence of it working, and some evidence that it doesn't work.
I didn't have to go far. You defined "chelation properties" with a link to:
It is a review of the evidence. It covers cilantro:
(iv) Cilantro (leaves of Coriandrum sativum), a popular culinary and medicinal herb, gained attention when a soup was reported to enhance mercury excretion following dental amalgam removal and remains popular despite limited evidence [46]. In animals, it decreased lead absorption into bone and inhibition of the delta-aminolevulinic acid dehydratase (ALAD) enzyme [47]. Less encouragingly, in a recent trial in 3- to 7-year old children exposed to lead, a cilantro extract was as effective as placebo in increasing renal excretion (improvements across treatment and placebo groups were ascribed to improved diet during the intervention) [48].