In low grade copper, copper is present in very less amount. It can be extracted by using acid. In presence of acid copper goes into solution in the form of Cu2+ ions.
2Cu() + 2H2SO4(aq) + O2(g) → 2CuSO4(aq) + 2H2O(l)
or
Cu() + 2H+(aq) + (\frac { 1 }{ 2 }) O2(g) → Cu2+(aq) + H2O(l)
