#Outlier Removal Function
remove_outliers <- function(dataframe, column, na.rm = TRUE) {
  Q1 <- quantile(column, .25)
  Q3 <- quantile(column, .75)
  IQR <- IQR(column)
  dataframe <- subset(dataframe, column> (Q1 - 1.5*IQR) & column< (Q3 + 1.5*IQR))
}

#Not looping
df_1 <-remove_outliers(df_1,df_1$Column1)

#Loop through a list of column names
for(i in Column_List){
  df_1 <- remove_outliers(df_1, df_1[[i]])
}