xa0.R

text <- "Ammonium\xa0tetrathiomolybdate"
text <- iconv(text, from = "latin1", to = "UTF-8")
text <- gsub("\u00A0", " ", text)
print(text)

## [1] "Ammonium tetrathiomolybdate"

################method_2
text <- iconv(text, from = "latin1", to = "UTF-8", sub = " ")
text

## [1] "Ammonium tetrathiomolybdate"