Abstract: Copper ion adsorption conditions by asparagus lettuce leaf residue were optimized through quadratic regression orthogonal design. A quadratic regression orthogonal model was established to express relationship between adsorption rate (Y) and five factors including addition amount (X1), concentration (X2), time (X3), pH (X4), and temperature (X5). The relationship was shown in the following equation: Y ＝85.45862＋11.80098X1－6.85546X2＋0.24918X3＋2.14203X4＋1.12124X5－4.75315X12－2.40953X22－2.23141X32－1.49228X42－3.40533X52＋3.84570X1X2＋0.61717X1X3－3.15888X1X4－0.26948X1X5－0.29760X2X3＋0.77899X2X4－0.01867X2X5－0.23965X3X4－1.45840X3X5＋0.94533X4X5. The factor order on Cu2＋ adsorption rate from strong to weak was addition amount, concentration, pH, temperature and time. According to this model, conditions under 0.9 g addition amount of asparagus lettuce leaf residue in 30 mg/L for 5 h using pH 3 and 40 ℃ revealed the highest adsorption, which was 98.40%. The experiment result was consistent with the theoretical result of 97.96%. The best solid to liquid radio of Cu2＋ adsorption by asparagus lettuce leaf residue is 12 g/L. In the low concentration of Cu2＋ solution, the adsorption of asparagus lettuce leaf residue is better than activated carbon.

Key words: asparagus lettuce leaf residue, Cu2＋, adsorption, optimization, quadratic regression orthogonal design, solid to liquid radio