The Mayor of the District of Columbia, upon the nomination of the Board, is hereby authorized to appoint a Director of Public Welfare, which position is hereby authorized and created, who shall be the chief executive officer of the Board and shall be charged, subject to its general supervision, with the executive and administrative duties provided for in this act. The Director shall be a person of such training, experience, and capacity as will especially qualify him or her to discharge the duties of the office. The Director of Public Welfare may be discharged by the Mayor of the District of Columbia upon recommendation of the Board. The Mayor of the District of Columbia is authorized, upon the nomination of the Board, to appoint such personnel as may be necessary for the efficient performance of the duties of the Board.