Adsorption of Cd2+ from aqueous solution by modified corn straw biochar and peanut shell biochar
Biochars produced from corn straw and peanut shell were modified using KMnO4 solution.A laboratory experiment was conducted to investigate the adsorption of Cd2+ in simulated wastewater,and the effects of initial concentrations of Cd2 +,pH values,and contact time on adsorption.Under conditions of pH 6.0,initial Cd2+ concentration 100 mg·L-1,wastewater temperature 20℃,contact time 12 h,and biochar dosage of 1.0 g · L-1,modified corn straw biochar and peanut shell biochar achieved cadmium removal rates of 67.03％ and 46.10％,respectively.These removal rates were respectively 3.8 and 6.2 times those achieved with unmodified biochars.The adsorption process of modified corn straw biochar and peanut shell biochar can be fitted by Langmuir and Freundlich models.Using the Langmuir equation,the theoretical maximum adsorbance of modified corn straw biochar is 68.97 mg · g-1 and that of peanut shell biochar is 55.55 mg · g-1 The adsorption process of the two types of biochars could be well described by a pseudo-second-order reaction kinetics model,which indicated that the adsorption was mainly chemical.Cd2+ adsorbed onto the two types of biochar can be easily desorbed by using NaOH solution.After being recycled four times,the two biochars retained 31.40 and 24.10 mg · g-1 adsorption capacity for Cd2+.To summarize,corn straw biochar and peanut shell biochar modified by KMnO4 solution have high adsorption capacities for Cd2+ in solution and can beutilized repeatedly.
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