Environmentally Benign Adsorption Materials for Removing Arsenic from Aquatic Environment

Adsorptive removal of arsenic using adsorption gels prepared from orange and apple juice residues was reviewed by summarizing the authors’ previous papers. Orange and apple juice residues contain a large amount of pectin, partly methyl-esterified pectic acid, which exhibits high affinity for high-valent metal ions such as iron(III), rare earths(III) and zirconium(IV). Anionic species of arsenic(III, V) are effectively and selectively adsorbed on pectic acid gel via loading these high-valent metal ions. Raw orange juice residue was saponified using calcium hydroxide to improve the loading capacity for these metal ions. It was found that zirconium(IV) exhibits the most suitable adsorption behaviors for arsenic(III, V). Similar result was obtained also for apple juice residue. An actual sample of acid mine drainage from the Horobetsu mine which contained a high concentration of iron and low concentration of arsenic, was tested using the adsorption gel prepared from orange juice residue and the results were compared with those from the current treatment process based on coprecipitation with iron hydroxide. The new process using the above- mentioned adsorption gel was proposed for treatment of such acid mine drainage.

Surface Modification of the Biowaste for Purification of Wastewater Contaminated with Toxic Heavy Metals—Lead and Cadmium

The surface of a biowaste was modified by introduction of amino group for the purification of wastewater contaminated with heavy metals. In this study waste tea leaf was used as a biowaste which was an economic and efficient bioadsorbent. The aminated tea leaves were characterized by spectral and elemental analysis. The adsorption capacity of the surface modified biosorbent was studied as the function of solution pH, concentration of metal ions and contact time of adsorption. The applicability of Langmuir isotherm was tested. The adsorption capacities were found to be 83.04 mg/g and 57 mg/g for Pb (II) and Cd (II), respectively. The biosorbent was regenerated by desorption of the metal loaded adsorbent with 0.1 M HNO3. These results showed that the aminated tea leaves may be an attractive alternative for treatment of wastewater contaminated with heavy metals.

Adsorptive Removal of Heavy Metals from Aqueous Solution with Environmental Friendly Material—Exhausted Tea Leaves

In this study adsorptive removal of Pb(II) and Cu(II) from aqueous solution by using environmental friendly natural polymers present in exhausted tea leaves has been studied. The biosorbent was modified with dimethylamine to introduce N-functional groups on the surface of adsorbent. The modified adsorbent was characterized by elemental analysis, zeta potential analysis, SEM, DRFTIR, XRD and TG/DTA analysis to conform the modification. Adsorption capacity of the adsorbent was determined as the function of pH of the solution, initial concentration of the solution and contact time. The adsorption experiments were performed using batch experiments. The maximum adsorption capacities of the adsorbent were found to be 91.68 and 71.20 mg/g for Pb(II) and Cu(II), respectively. To minimize the process cost, regeneration of the biosorbent and recovery of metal ions was explored by desorption study. The results indicate that the adsorbent holds great potential for the sequestration of Pb(II) and Cu(II) from their aqueous solution. Hence the modified exhausted tea leaves (MTL) have been investigated as a new cost effective and efficient biosorbent for removal of Pb(II) and Cu(II) from their aqueous solution.