Kedar Nath Ghimire

Removal and recovery of phosphorus from water by means of adsorption onto orange waste gel loaded with zirconium

Orange waste, an available biomass, was immobilized with zirconium(IV) to investigate its feasibility for phosphate removal from an aquatic environment. Kinetics, effects of pH and foreign anions, and the adsorption isotherm for phosphate have been examined. The adsorption capacity has been compared to that of two commercially available adsorbents such as zirconium ferrite and MUROMAC XMC 3614. The prepared gel was an effective adsorption gel for phosphate removal with a reasonably high sorption capacity of 57mg-P/g, which was four times higher than that of zirconium ferrite. The highest removal of phosphate was observed at low pH, whereas higher pH suppressed phosphate removal, but even up to pH 9 more than 85% phosphate removal was observed. Adsorbed phosphate was eluted by NaOH solution. Fixed bed column-mode experiments confirmed the complete adsorption of phosphate in continuous-mode operation. Throughout the operating conditions, zirconium was not leaked.

ADSORPTIVE REMOVAL OF ARSENIC USING ORANGE JUICE RESIDUE

A novel adsorbent has been prepared by simple chemical modification of orange juice residue (OJR) with the substitution of phosphate groups on the alcoholic analog of cellulose. Phosphorylated gel was further loaded with iron(III). The loading capacity for iron(III) on the gel was as high as 3.7 mol/kg. Adsorption studies on iron(III) loaded gel were carried out both batch wise and by using a column. Arsenic(III) adsorption was found to have been favored at alkaline condition (pH=7–11) while that of arsenic(V) was at acidic condition (pH=2–6). Maximum adsorption capacity for As(V) and As(III) was evaluated as 0.94 and 0.91 mol/kg at their optimum pH values 3.1 and 10.0, respectively. Experimental results indicate that iron-loaded phosphorylated OJR can be potentially applied for the removal and recovery of arsenic from various aqueous media.

Adsorptive Separation of Metallic Pollutants onto Waste Seaweeds, Porphyra Yezoensis and Ulva Japonica

Abstract From two kinds of seaweeds, Porphyra yezoensis and Ulva japonica, adsorption gels for heavy metal ions were prepared by enhancing their adsorptive properties and diminishing the aqueous solubility. An environmental benign crosslinking using calcium have shown maximum adsorption capacity of 0.67 mol/kg dry gel for lead(II), which is slightly lower as compared to the adsorbents crosslinked with synthetic crosslinking agent (0.76 mol/kg). Fixed bed column studies for a binary mixture containing lead(II) and zinc(II) revealed that lead(II) can be mutually separated from zinc(II) with a concentration factor of 45.

Adsorptive Separation of Metal Ions onto Phosphorylated Orange Waste

Abstract A highly selective and efficient biosorbent has been prepared from orange waste by introducing a phosphoric group at its polymer analog by simple chemical modification. Their adsorption behavior for several kinds of metal ions was studied and it was found to exhibit excellent selectivity towards several metal ions. As a typical example, a binary mixture of In(III) and Zn(II) was studied by using a packed column, indicating that In(III) ion can be selectively separated from its mixture with a concentration factor of 63 times. The maximum adsorption capacities evaluated in terms of mol/kg dry gel were 0.70 for In(III) and Ga(III), 0.97 for Cu(II), 1.15 for Pb(II) and Zr(IV), and 3.06 for Fe(III), respectively.

Effective Removal of Arsenic with Lanthanum(III)- and Cerium(III)-loaded Orange Waste Gels

Abstract Orange waste has been chemically modified and loaded with lanthanum(III) and/or cerium(III) to examine its adsorption behavior to both As(V) and As(III). Arsenate removal was found to be favored over a pH range of 6 ∼ 9.5 while arsenite removal took place at pH values ranging from 9 to 11. The maximum sorption capacity of the gel for As(III) removal was evaluated as 43 mg/g, while that for As(V) was 42 mg/g. Column-mode tests using the La(III)-loaded gel confirmed a complete removal of As(V). A reasonably high adsorption potential within the design criteria makes the present gel an alternative choice for arsenic removal.

Effective Use of Orange Juice Residue for Removing Heavy and Radioactive Metals from Environments

ABSTRACT Large amounts of orange juice are produced in Japan every year. Accompanied by the production of orange juice, large amount of juice residues are also generated in nearly the same amounts with juice. Although, at present, some of these residues are marketed as a feed for cattle after drying and mixing with lime, the marketing price is lower than its production cost and the difference is paid by the consumers as a part of the price of orange juice. In the present work, we developed new innovative use of orange juice residue, a biomass waste, as adsorption gel for removing toxic heavy metals such as lead, arsenic, selenium and so on as well as radioactive elements such as uranium and thorium from environments. The major components of orange juice residue are cellulose, hemicellulose and pectin, which are converted into pectic acid, an acidic polysaccharide, by means of saponification with concentrated sodium hydroxide solution. In the previous work, we found that crosslinked pectic acid gel strongly and selectively adsorbs lead over other metals such as zinc and copper. On the other hand, it is well known that polysaccharides such as cellulose can be easily phosphorylated and that phosphorylated polysaccharides have high affinity to uranium and thorium as well as some trivalent metals such as ferric iron and aluminum. Taking account of the noticeable characteristics of these polysaccharides, 2 types of adsorption gels were prepared from orange juice residue: one is the gel which was prepared by saponificating the residue followed by crosslinking with epichlorohydrin and another is that prepared by crosslinking the residue followed by phosphorylation. The former gel exhibited excellent adsorptive separation behavior for lead away from zinc owing to high content of pectic acid while the latter gel exhibited that for uranium and thorium. Both types of adsorption gels exhibited high affinity to ferric iron, which enables selective and strong adsorption for some toxic oxo-anions of arsenic (V and III), selenium and so on via iron loaded on these gels. These results demonstrate that biomass wastes such as orange juice residue can be effectively utilized for the purpose of removing toxic heavy or radioactive metals existing in trace or small amounts in environments.

Effectiveness of phosphorylated orange residue for toxic oxo-anion removal

Two kinds of adsorption gels have been prepared by the phosphorylation of orange juice residue having 2.68 and 4.96 mol of phosphorus/ kg dry gel, respectively. The latter exhibited a higher adsorption capacity for the removal of oxo anions such as arsenic and selenium after loading them with ferric iron. The maximum adsorption capacity of the former and latter gels loaded with ferric iron for arsenic(V) was 0.53 and 0.94 mol/kg dry gel, and for selenium(IV) 0.37 and 0.51 mol/kg dry gel, respectively. The batchwise results revealed that phosphorylated orange juice residue can be used as an effective adsorbent for the treatment of wastewater contaminated with oxo anions.

Biosorbents for Removing Hazardous Metals and Metalloids

Biosorbents for remediating aquatic environmental media polluted with hazardous heavy metals and metalloids such as Pb(II), Cr(VI), Sb(III and V), and As(III and V) were prepared from lignin waste, orange and apple juice residues, seaweed and persimmon and grape wastes using simple and cheap methods. A lignophenol gel such as lignocatechol gel was prepared by immobilizing the catechol functional groups onto lignin from sawdust, while lignosulfonate gel was prepared directly from waste liquor generated during pulp production. These gels effectively removed Pb(II). Orange and apple juice residues, which are rich in pectic acid, were easily converted using alkali (e.g., calcium hydroxide) into biosorbents that effectively removed Pb(II). These materials also effectively removed Sb(III and V) and As(III and V) when these were preloaded with multi-valent metal ions such as Zr(IV) and Fe(III). Similar biosorbents were prepared from seaweed waste, which is rich in alginic acid. Other biosorbents, which effectively removed Cr(VI), were prepared by simply treating persimmon and grape wastes with concentrated sulfuric acid.

Adsorptive Separation of Toxic Anions from Water Using Phosphorylated Orange Juice Residue

Arsenic, selenium, and phosphorus are among the serious water pollutants specifically generated in the effluents of mineral and chemical industries. In addition, arsenic pollution has also been serious in some ground water or hot spring water over a large area in Bangladesh, West Bengal in India, Inner Mongolia in China, and Japan as well. To date, arsenic and selenium have been removed by means of the following methods: precipitation with lime, co-precipitation with ferric sulfate, alum precipitation, and precipitation as sulfide using either sodium sulfide or hydrogen sulfide. Although among these methods the iron co-precipitation method has been reported to be the most successful in lowering arsenic content to the drinking-water standard level, it still suffers from a post-treatment problem due to the excess use of Fe(III) salt and generation of alkaline sludge of high water content.1 Since it is difficult to remove As(III) directly by traditional methods, it should be oxidized into the pentavalent state prior to their treatment by using suitable oxidizing agents like hydrogen peroxide.2