split multiple columns in pandas dataframe by delimiter

We can use list comprehension with add_prefix, then we use pd.concat to concatenate everything to your final df:

splits = [df[col].str.split(pat='/', expand=True).add_prefix(col) for col in df.columns]
clean_df = pd.concat(splits, axis=1)

     q10  q20  q21    q22 q30 q31 q32
0    one  one  two  three   a   b   c
1    two    a    b      c   d   e   f
2  three    d    e      f   g   h   i

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If you actually want your column names to be suffixed by a letter, you can do the following with string.ascii_lowercase:

from string import ascii_lowercase

dfs = []
for col in df.columns:
    d = df[col].str.split('/', expand=True)
    c = d.shape[1]
    d.columns = [col + l for l in ascii_lowercase[:c]]
    dfs.append(d)
    
clean_df = pd.concat(dfs, axis=1)

     q1a  q2a  q2b    q2c q3a q3b q3c
0    one  one  two  three   a   b   c
1    two    a    b      c   d   e   f
2  three    d    e      f   g   h   i