[1] Nnamdi Azikiwe Univ, Dept Pure & Ind Chem, Awka, Nigeria
[2] Fed Univ Petr Resources, Dept Mech Engn, Tori, Nigeria
[3] Univ Johannesburg, Dept Mech & Ind Engn, Johannesburg, South Africa
[4] Univ Nigeria Nsukka, Dept Pure & Ind Chem, Nsukka 410001, Nigeria
[5] UCL, Fac Math & Phys Sci, Dept Chem, London WC1E 6BT, England
[6] Univ Nigeria Nsukka, Dept Pure & Ind Chem, Nsukka 410001, Nigeria