Figure 4: Effect of pH on adsorption of Pb(II), Cd(II) and Cu(II) onto raw wheat straw. (metal concentration: 50 mg/L; contact time: 15 min; agitation speed: 100 rpm; temperature: 303 K; dose: 0.4g/50mL for Pb(II), 0.6g/50mL for Cd(II) and Cu(II)).