A low pressures, the compression factor of CO₂ having constant value of molar volume

According to van der Waals equation,
(P+aV²)(V−b)=RT
At very low pressure, volume (V) is very large. Hence, a / V² is so small that it can be neglected. Similarly, volume correction term .b can also be neglected in comparison to V. Thus, the above equation reduces to PV = RT. Hence, at very low pressure a real gas behaves like ideal gas.

therefore volume increases with increase in temperature.