<p class=\"MsoNormal\" style=\"text-align: justify; line-height: 150%; mso-layout-grid-align: none; text-autospace: none;\">The discharge of heavy metals into aquatic ecosystems has become a matter of concern in India over the last few decades. These toxic heavy metals are generated from operations involved in mining, sludge disposal, refining ores, metal plating, battery industries etc. An attempt was made to compare the effective removal efficiency of heavy metals such as chromium (VI) and Nickel (II) from aqueous solutions using Parthenium hysterophorus as adsorbent. Batch adsorption experiments were performed as a function of pH, contact time, solute concentration and adsorbent dosage. Maximum removal of Cr (VI) was achieved at pH 3&plusmn;0.5, whereas Ni (II) had an optimum pH of 5&plusmn;0.2. At pH higher than 7&plusmn;0.5 for both metals precipitation occurred, due to this reason adsorption was not studied beyond pH of 7&plusmn;0.5. The equilibrium time for Cr (VI) and Ni (II) were found to be 165 and 180 minutes respectively. The removal efficiency for Cr (VI) and Ni (II) using Parthenium hysterophorus powder as adsorbent are 80.43% and 81.54% respectively. The optimum dosage for maximum Cr (VI) and Ni (II) are 4 g and 3.5 g respectively. Experimental equilibrium adsorption data were tested for the Langmuir and Freundlich equations/isotherms but found that the Freundlich isotherm best fitted with experimental data for both Cr (VI) and Ni (II). Kinetics of adsorption for both Cr (VI) and Ni (II) was found to follow Lagergren first order model.</p>
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<p class=\"MsoNormal\" style=\"text-align: justify; line-height: 150%;\"><strong>Keywords:</strong> Adsorption, heavy metals, adsorbents, equilibrium isotherms, adsorption kinetics,&nbsp;Parthenium hysterophorus.</p>