Search

Humic Substances (HS) from Leonardite and two different composts were used as biosurfactants to wash heavy metals (Cu, Pb, Zn, Cd, Cr) from a soil added with two metals concentrations and aged for 4 and 12 months. Composts were obtained by mixing manure with either 40 (CM-I) and 20 (CM-II) % of straw as structuring material. For both aging periods and both metal concentrations, HS from CM-I removed more metals than from Leonardite, whereas the washing capacity of HS from CM-II was negligible. 13C-CPMAS-NMR spectra of HS indicated that while aromatic moieties for CM-I and Leonardite were more abundant than CM-II, HS from CM-I was largest in carboxyl and phenolic carbons. Hence, HS from CM-I had a greater complexing capacity than from both Leonardite and CM-II and effectively displaced heavy metals from soil during the washing treatment. Moreover, the amount of metals removed by solutions of ammonium acetate (AA) and diethylenetriaminepentaacetic acid (DTPA), was found invariably smaller than by HS from CM-I, thereby indicating that HS removed more than one metal specie. The combined washing with HS from CM-I before and after soil treatment by either AA and DTPA revealed significant larger metal removals than by single solutions alone. This shows that humic soil washing also renders residual metals potentially more available to subsequent soil remediation approaches, such as phytoextraction. These results suggest a novel, efficient, and molecularly-based technology to remediate soils from heavy metals can be based on a low-cost and sustainable humic matter produced from recycled biomasses.

The X-ray diffraction spectra of liquid chloromethyl-oxirane (ClMO) and chloromethyl-thiirane (ClMT) have been recorded for the first time. The interpretation of X-ray measurements was based on ab initio molecular dynamics simulations at finite temperature conditions. Both liquids show conformational equilibrium, which is discussed in terms of Gauche-2, Gauche-1 and Cis structures. The occurrence of the various forms estimated from X-ray and AIMD data has been compared with spectroscopy data from the literature, with the FTIR spectra of the liquids newly recorded in this work, and with theoretical in vacuo calculations.

Dihydrogenarsenate [H(2)AsO(4)(-), As(V)] or dichromate [Cr(2)O(7)(2-), Cr(VI)] at pH=4.0 showed to be sorbed on a Fe(OH)(x)-polymerin complex and ferrihydrite to a greater extent than on polymerin, the organic polymeric fraction of olive oil mill wastewater (OMW). In particular, the maximum amount (x(m)) of arsenate sorbed on Fe(OH)(x)-polymerin complex was similar to that on ferrihydrite (880.26 and 743.02 mmol kg(-1), respectively), and was much greater than that sorbed on polymerin (384.25 mmol kg(-1)). The sorption of dichromate was to a comparable extent on Fe(OH)(x)-polymerin complex and ferrihydrite (205.90 and 254.88 mmol kg(-1), respectively). Cr(III), a less toxic chromium form, mainly, and Cr(V) were indeed the effective forms sorbed on polymerin (200 mmol kg(-1)), as a consequence of the redox reaction of the strongly toxic Cr(VI) with the CH(2)OH groups of the polysaccharide moiety of this bio-sorbent, according to the data deriving from XPS and DRIFT analyses. The potential exploitation of the selected sorbents for the removal of As(V) or Cr(VI) from aqueous effluents is briefly discussed.

A comparative study was performed on the sorption capacity of the phenoxy acid herbicide cyhalofop on polymerin (from olive oil mill effluents), ferrihydrite, and a ferrihydrite-polymerin complex, by using a batch equilibrium method. The most efficient sorbent showed to be ferrihydrite followed by the ferrihydrite-polymerin complex and polymerin. Cyhalofop acid bound to ferrihydrite by a combination of ionic and ion-dipole bonding, whereas the same herbicide bound to the ferrihydrite-polymerin complex by ionic bonding and to polymerin by hydrogen bonding. Simulated wastewaters contaminated with cyhalofop acid were completely purified by two sorption cycles on ferrihydrite and five cycles on the ferrihydrite-polymerin complex, whereas the same wastewaters maintained a constant residue even after five sorption cycles on polymerin. For the first time, the possible use of a mineral (ferrihydrite) and an organo-mineral complex (ferrihydrite-polymerin) as a filter for the control of the herbicide contamination in point sources is proposed and briefly discussed.

In a greenhouse pot experiment, lettuce plants (Lactuca sativa L.) were grown in a Hg-contaminated sandy soil with and without inoculation with arbuscular mycorrhizal fungi (AMF) (a commercial inoculum containing infective propagules of Rhizophagus irregularis and Funneliformis mosseae) amended with different rates of a humic acid (0, 1, and 2 g kg(-1) of soil), with the objective of verifying the synergistic effects of the two soil treatments on the Hg tolerance of lettuce plants. Our results indicated that the plant biomass was significantly increased by the combined effect of AMF and humic acid treatments. Addition of humic matter to soil boosted the AMF effect on improving the nutritional plant status, enhancing the pigment content in plant leaves, and inhibiting both Hg uptake and Hg translocation from the roots to the shoots. This was attributed not only to the Hg immobilization by stable complexes with HA and with extraradical mycorrhizal mycelium in soil and root surfaces but also to an improved mineral nutrition promoted by AMF. This work indicates that the combined use of AMF and humic acids may become a useful practice in Hg-contaminated soils to reduce Hg toxicity to crops.

High-performance anion exchange chromatography coupled with pulsed amperometric detection was used for the quantitative determination of total and free sugars in olive oil mill waste waters (OMWW). Automated amino acid ion chromatography was employed to analyse total and free amino acids in the same OMWW. Sugars were analysed in samples pre-purified by means of a three-step purification procedure involving: (i) methanol precipitation of OMWW; (ii) dialysis of the obtained solid and liquid fractions; and (iii) chromatographic purification on RP18 phase followed by Amberlite resin. The amino acids were determined directly in samples obtained from the first two steps performed for sugar analysis. The analysis carried out with the reported methodologies allowed the quantitative determination of total sugars and amino acids and the differentiation between their free and bound forms. The sugars determined were arabinose, fructose, galactose, glucose, rhamnose, xylose, galacturonic and glucuronic acids, and the amino acids were Asp, Glu, Thr, Ser, Pro, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Arg and Cys. Asn, Gln, and Trp were not detected. The technological, biotechnological and environmental advantages arising from this analytical methodology applied to OMWW are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd.

Electrochemical peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H2O2, was used to remove As(III) from contaminated aqueous solutions. Bench scale experiments were conducted to evaluate the sorption and distribution of arsenic between the soluble and solid state hydrous ferric oxides (HFO) formed as part of the ECP process. ECP was effective in removing arsenic from the aqueous solution, with98% of the applied As(III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water (3.5-9.5). In the absence of H2O2 more As(III) was adsorbed by solid state iron at pH 9.5 than at 3.5 (2600 vs. 1750 microg l(-1)). Thus H2O2 was crucial to oxidize As(III) to As(V) which is more strongly retained by HFO. Removal of As was not significantly affected by the concentration of H2O2 or by current processing time. The optimal operating conditions were pH6.5, H2O2 concentration of 10 mg l(-1) and current process time not exceeding 3 min. X-ray diffraction (XRD), diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy and transmission electron microscopy (TEM) were applied to study the HFO deposits. The XRD data indicated the prevalence of poorly ordered Fe minerals in the suspended ECP solids with a dominance of 5 line ferrihydrite in the absence of H2O2. At pH 3.5 and with 100 mg H2O2 l(-1), akaganeite was formed, whereas an incipient hematitic phase, reflection at 0.39 nm, occurred at pH 6.5. DRIFT data indicate that both As(III) and As(V) were specifically adsorbed onto HFO at acid and neutral pH. TEM observations indicated the presence of spherical shape ferrihydrite and provided evidence for possible formation of subrounded hematite and acicular shape goethite.

Disposal of olive mill waste waters (OMWW) represents a serious problem due to its elevated toxicity and pollution risk for environmental and aquatic bodies, which is mainly related to its polyphenol content. The use of layered double hydroxides (LDHs) or anionic clays for OMWW detoxification may represent an effective remediation process. In the current study, OMWW was treated with cold methanol to obtain a dark humic acid-like precipitate made of high molecular weight organic compounds named polymerin and a supernatant made of low molecular weight organics named OMWW-S. After precipitation with methanol, phenol content decreased from 2.14 g L−1 to 0.80 and 1.20 g L−1, in polymerin and OMWW-S, respectively. The chemical oxygen demand of OMWW-S decreased by about 30% with respect to raw OMWW, from 62.2 to 40.2 g L−1. A phenolic concentrate, named OMWW-E was also obtained by ethyl acetate extraction of OMWW-S at pH 2.0. LDHs of zinc and aluminium (LDH) were obtained at room temperature and after calcination at 450 °C (LDH-450). An organo-mineral complex of LDH with polymerin (LDH-Pol) was also synthesised. Phenols from OMWW-E were sorbed preferentially on three matrices according to the following order: LDH-450 > LDH > LDH-Pol, with percent sorption of up to 73% for LDH-450. Repeated cycles of sorption of OMWW-S onto LDH-450 decreased phenol concentration by about 90%. Use of remediated water in a phytotoxicity bioassay revealed scant inhibition of germination and coleoptile elongation rate in tomato seeds and seedlings. Thus, OMWW-S after sorption onto LDH-450 could represent a low cost source of irrigation water for arid soil of the Mediterranean region.

Polymerin is a humic acid-like polymer, which we previously recovered for the first time from olive oil mill waste waters (OMWW) only, and chemically and physicochemically characterized. We also previously investigated its versatile sorption capacity for toxic inorganic and organic compounds. Therefore, a review is presented on the removal, from simulated polluted waters, of cationic heavy metals [Cu(II), Zn, Cr(III)] and anionic ones [Cr(VI)) and As(V)] by sorption on this natural organic sorbent in comparison with its synthetic derivatives, K-polymerin, a ferrihydrite-polymerin complex and with ferrihydrite. An overview is also performed of the removal of ionic herbicides (2,4-D, paraquat, MCPA, simazine, and cyhalofop) by sorption on polymerin, ferrihydrite, and their complex and of the removal of phenanthrene, as a representative of polycyclic aromatic hydrocarbons, by sorption on this sorbent and its complexes with micro- or nanoparticles of aluminum oxide, pointing out the employment of all these sorbents in biobed systems, which might allow the remediation of water and protection of surface and groundwater. In addition, a short review is also given on the removal of Cu(II) and Zn from simulated contaminated waters, by sorption on the humic acid-like organic fraction, named lignimerin, which we previously isolated for the first time, in collaboration with a Chilean group, from cellulose mill Kraft waste waters (KCMWW) only. More specifically, the production methods and the characterization of the two natural sorbents (polymerin and lignimerin) and their derivatives (K-polymerin ferrihydrite-polymerin, polymerin-microAl(2)O(3) and -nanoAl(2)O(3), and H-lignimerin, respectively) as well as their sorption data and mechanism are reviewed. Published and original results obtained by the cyclic sorption on all of the considered sorbents for the removal of the above-mentioned toxic compounds from simulated waste waters are also reported. Moreover, sorption capacity and mechanism of the considered compounds on polymerins and lignimerins are evaluated in comparison with other known natural sorbents, especially of humic acid nature and other organic matter. Some of their technical aspects and relative costs are also considered. Finally, the possible large-scale application of the considered sorption systems for water remediation is briefly discussed.

The dark polymeric organic fraction rich in potassium recovered from olive oil mill waste waters (OMWW) and named polymerin and the potassium salified deglycosylated polymerin derivative (K-SDpolymerin) were easily transformed into their metal derivatives by saturation with various metals, including Na, Cu, Zn, Mn, Fe, and Al. Saturated metal polymerins were characterized by diffuse reflectance infrared Fourier transform spectroscopy and atomic absorption spectrometry. Tests on tomato plants of the various polymerins showed that only the soluble polymerin, K-SDpolymerin, and the insoluble Mn-SDpolymerin were significantly toxic. The toxic effects of OMWW on tomato at the original concentration and diluted 1:10 were much stronger than those of any polymerin. The possible exploitation of polymerins as bioamendments and/or metal biointegrators as a functon of their phytotoxic effects, their humic acid-like nature, and their richness in macro- and micronutrient metals is also discussed.

In light of the growing interest for eco-compatible fertilization, tomato plant roots were treated with four different strains of microorganisms (B1–B4) capable of positively affecting plant growth. The methanolic extracts from treated roots were analysed by reverse phase ultra-high-performance liquid chromatography hyphenated with ion trap time-of-flight high-resolution mass spectrometry to compare their metabolites with that of control plants (B0). We found, in both treated and control plants, several primary metabolites, such as fatty acids and coumaric acid, and other compounds associated with secondary metabolism pathways such as that of cyclopentaneoctanoic acid (CPOA) or hydroxyoctadecadienoic acid (HODE), and additional molecules which were not characterizable with the available data. A semiquantitative assessment of all metabolites became the basis for further processing the metabolic results by principal component analysis, which highlighted significant differences in the PC1 and PC2 components. The PC1 was particularly affected by the presence of arachidonic acid, myristic acid, and two unidentified metabolites. It effectively differentiated control plants from all bioeffectors treatments, and, in particular, the B4 treatment from the rest (B1–B3). The PC2 was mainly affected by palmitic acid, heptadecanoic acid, two CPOAs, one HODE and two unidentified metabolites. These metabolites successfully differentiated the B0 control from all the bioeffectors treatments, and, especially, showed a difference between B1 and B2. Our findings suggest that changes in secondary pathways of lipid metabolism may underlie the biostimulation exerted by the four microbial bioeffectors of this study, and that LC–MS coupled by multivariate analysis can easily fingerprint the metabolic alterations induced by bioeffectors in tomato roots.