The photochemical degradation of two azo and two anthraquinonic dyes was performed using potassium peroxymonosulphate (Oxone®) activated by UV radiation. The fast decolourization of all dyes was observed within 6 min of UV irradiation, with corresponding dye decays higher than 80%. The kinetic rate constants of the dyes' decay were determined, along with the energetic efficiency of the photochemical treatment, taking into account the influence of a few anions commonly present in real wastewaters (i.e., chloride, nitrate, carbonate/bicarbonate and phosphate ions). Chloride and carbonate/bicarbonate ions enhanced dye degradation, whereas phosphate ions exerted an inhibitory effect, and nitrates did not have a predictable influence. The dye decolourization was not associated with efficient mineralization, as suggested by the lack of a significant total organic carbon (TOC) decrease, as well as by the low concentrations of a few detected low molecular weight by-products, including nitrate ions, formaldehyde and organic acids. High molecular weight by-products were also detected by mass spectrometry analysis. The investigated process may be proposed as a convenient pre-treatment to help dye degradation in wastewater during combined treatment methods.

The degradation of two of the most frequently used UV-filters was investigated through microcosm studies. Marine sediments sampled from two sites in Italy (La Spezia harbour and Sarno river estuary, S1 and S2 respectively) were used to set up aerobic and anaerobic sets of reactors. The sediments were spiked with a methanol solution of 3-(4-methylbenzylidene)camphor (4-MBC) and 2-ethylhexyl 4-(dimethylamino)benzoate (EH-DPAB), at concentrations of either 25 or 50mgkg-1 each. Methanol (6.3g/L) also served as an organic amendment and growth substrate for improving microbial activity. Monitoring of the biotic and abiotic degradation of the selected contaminants over 16months revealed that 4-MBC biodegradation was very slow and incomplete, whereas over 90% of EH-DPAB was degraded both in the aerobic and the anaerobic reactors by the natural microbial communities of both sediments. Repeated spikes of EH-DPAB were followed by complete decay, characterised by first-order kinetics. The calculated kinetic rate constants under aerobic and anaerobic conditions were similar. In reactors inoculated with the S1 sediment the degradation rate constants progressively increased after each spike, up to the value of 0.039d-1. For the S2 sediment the rate constant was around 0.020d-1 throughout the duration of the experiment. Mass spectrometry analysis of sediment extracts allowed detection of potential transformation products of EH-DPAB and 4-MBC. Moreover, the natural microbial community of the sediments was studied using the CAtalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) both in the initial sediments and after degradation under aerobic and anaerobic conditions.

Titanates may be selectively used as inorganic adsorbents for heavy metal ions owing to their stability and fast adsorption kinetics. Nevertheless, the synthesis of such materials usually requires extreme reaction conditions. In this work, a new titanium-based material was rapidly synthesized under mild laboratory conditions. The obtained amorphous hydroxo titanate was tested for heavy metal sorption through kinetic and equilibrium batch tests, which indicated that the new material had high adsorption rates and adsorption capacities towards Cu(2+), Ni(2+) and Pb(2) ions. Adsorption kinetics were pseudo-second order, and equilibrium data fitted the Langmuir isotherm model. The calculated maximum adsorption capacities of Cu(2+), Ni(2+) and Pb(2+) in deionized water were around 1 mmol g(-1), and they decreased for Cu(2+) and Ni(2+) in the presence of Na(+), Ca(2+) and Mg(2+) ions, whereas the alkali metal ions did not influence Pb(2+) uptake. The efficiency of adsorption and recovery of lead ions were evaluated through column dynamic tests, by feeding the column with groundwater and tap water spiked with Pb(2+). The high performance of the hydroxo titanate over several cycles of retention and elution suggested that the product is potentially useful for the solid phase extraction of lead at trace levels in natural water samples, with potential use in metal pre-concentration for analytical applications.

Amorphous titanium hydroxide and boron-doped (B-doped) sodium titanates hydrates were synthetized and used as adsorbents for the removal of Pb2+ from water. The use of sodium borohydride (NaBH4) and titanium(IV) isopropoxide (TTIP) as precursors permits a very easy synthesis of B-doped adsorbents at 298K. The new adsorbent materials were first chemically characterized (XRD, XPS, SEM, DRIFT and elemental analysis) and then tested in Pb2+ adsorption batch experiments, in order to define kinetics and equilibrium studies. The nature of interaction between such sorbent materials and Pb2+ was also well defined: besides a pure adsorption due to hydroxyl interaction functionalities, there is also an ionic exchange between Pb2+ and sodium ions even working at pH 4.4. Langmuir model presented the best fitting with a maximum adsorption capacity up to 385mg/g. The effect of solution pH and common ions (i.e. Na+, Ca2+ and Mg2+) onto Pb2+ sorption were also investigated. Finally, recovery was positively conducted using EDTA. Very efficient adsorption (>99.9%) was verified even using tap water spiked with traces of Pb2+ (50ppb).

Fat, oil and grease (FOG) recovered by the oil/water separator of a wastewater treatment plant (WWTP) were sampled, characterized, activated and converted into biofuel. Free acids (50-55%) and fatty soaps (26-32%) not only composed the main components, but they were also easily separable from the starting waste. The respective free fatty acid profiles were gas-chromatographically evaluated, interestingly verifying that free acids had a different profile (mainly oleic acid) with respect to the soapy fraction (saturated fatty acids were dominant). The inorganic composition was also determined for soaps, confirming that calcium is the most commonly present metal. The chemical activation of this fatty waste was made possible by converting the starting soaps into the respective free fatty acids by using formic acid as activator, coproducing the relevant formates. The activated fatty matter was then converted into biofuel through direct esterification under very mild conditions (345 K, atmospheric pressure) and obtaining thermodynamic conversion in less than 2 h. The process was easily scaled up, isolating at the end pure biodiesel (purity > 96%) through distillation under vacuum, providing a final product conformed to commercial purposes.

Some industrial wastewaters contain both hexavalent chromium and surfactants. In this work, their removal from aqueous solution by zero-valent iron (ZVI) and peroxymonosulphate (PMS) was studied using Brij 35 as a representative non-ionic surfactant. The performance of the ZVI/PMS system in the simultaneous removal of both pollutants was compared to that achieved with control solutions containing either Cr(VI) or Brij 35 separately. Reactions were carried out over 24 h at initial pH = 2.3 with variable initial amounts of Cr(VI) and Brij 35. The results showed that surfactant removal was enhanced in the system also containing Cr(VI). Surfactant degradation followed zero-order kinetics and produced formic acid as the main by-product, together with hydroxylated aldehydes, formates and alcohols that were identified by LC/MS. The presence of surfactant similarly enhanced Cr(VI) reduction, which also followed zero-order kinetics. Chromium removal was quantitative only when the initial chromium concentration was lower than 140 mg L−1. Reduced chromium was mainly in the solution phase together with dissolved iron. Precipitation with NaOH was therefore required to definitively remove dissolved metals from the investigated system.

The non-ionic surfactant Brij 35 was effectively removed from concentrated aqueous solution by the peroxymonosulfate/Co(II) system, using oxone (2KHSO5·KHSO4·K2SO4) as a source of peroxymonosulfate. At pH=2.3 and initial Brij 35 concentration in the range 680–2410mgL−1, 86–94% removal was achieved after 24h, using Co(II)=15μM and oxone=5.9mM. The effectiveness of removal did not change when initial pH was in the range 2.3–8.2. After five subsequent additions of Co(II) and oxone to the solution, COD and TOC removals increased up to 64% and 33%, respectively. Radical quenching tests confirmed that sulfate radical was the dominant radical species in the system. The main identified by-products from surfactant degradation were: (a) low molecular weight organic acids; (b) aldehydes and formates with shorter ethoxy chain than Brij 35; (c) alcohol ethoxylates carrying hydroxyl groups bonded to ethoxy chain. By-products identification allowed to hypothesize the pathways of Brij 35 degradation.

Fenton oxidation of the nonionic surfactant Brij 35 was enhanced by the effect of 1,4-hydroquinone adsorbed on granular activated carbon (GAC). The procedure allowed 90%-94% surfactant removal after 24 h at pH=2.7-3.0, using 97 mg g(-1) of hydroquinone adsorbed on GAC and concentrations of surfactant, H2O2, and iron (either Fe2+ or Fe3+) of, respectively, 1300, 450, and 9 mg L-1. In the absence of carbon and hydroquinone, and with the same concentration of H2O2, conventional Fenton process required 300 mg L-1 of Fe(II) to obtain 85% removal of Brij 35. Quinone-loaded carbon was effectively recycled until surfactant removal decreased to 50%-60%. Only 3% of hydroquinone was desorbed from GAC to the aqueous solution, and about 40% of the dissolved fraction was degraded to low-molecular-weight organic acids. This is the first description of a Fenton process performing the recycling of a redox-active organic compound adsorbed on GAC, with the aim of decreasing the amount of iron salt utilized in the conventional Fenton reaction.

Batch and column tests were conducted to compare the efficiencies of three Fenton‐like systems in the degradation of chlorobenzene. In the investigated systems, iron powder was the source of Fe2+ ions, and either Fe3+ or Cu2+ were added in order to enhance the degradation process. Optimum pH and concentrations of Fe3+, Cu2+ and hydrogen peroxide were assessed by treating synthetic chlorobenzene solutions both in batch and in column mode, thus achieving the minimum residual concentration of chlorobenzene. Optimum conditions assessed by means of column tests were then applied to column treatment of real chlorobenzene‐contaminated groundwater. Results showed that, when the TOC content of water was above 12 mg L−1, the performance of the Fe0/H2O2 system was enhanced by the addition of Fe3+, leading to 10–20 µg L−1 of residual chlorobenzene.

The present paper reports the results of an investigation aimed at evaluating the effectiveness of magnesium ammonium phosphate precipitation (MAP), commonly called struvite, for removing ammonia from a mature municipal landfill leachate. MAP precipitation was carried out at laboratory scale by adding phosphoric acid and magnesium oxide as external sources of phosphorus and magnesium, respectively, and regulating the pH at 9.0. The effect of Mg:NH4:PO3 ratio was studied. Due to the low solubility of MgO, a low ammonia removal efficiency (i.e. 67%), with a rather high residual concentration, was obtained when the stoichiometric molar ratio was applied. However, by doubling the amount of magnesium oxide (i.e. by using a molar ratio of 2:1:1), ammonia removal efficiency increased up to 95% with a residual concentration compatible with a successive biological treatment. The struvite produced in the present study showed a composition close to the theoretical one. Furthermore, the precipitate was characterized by a heavy metal content much lower than that of typical raw soil, excluding any concern about heavy metal contamination in the case of its use as a fertilizer. The economic analysis of the process showed that ammonia can be removed at a cost of 9.6 €/kg NH4–Nremoved. This value can be greatly reduced, however, if the value of the struvite produced is considered.

The paper reports the results of a laboratory-scale investigation aimed at evaluating the performance of a periodic biofilter with granular biomass (SBBGR) for treating leachate coming from a mature municipal landfill. The results show that the SBBGR was able to remove roughly 80% of COD in leachate. The remaining 20% of COD were, therefore, presumably owing to the presence in the leachate of recalcitrant compounds. Ammonia removal efficiency was low because of the presence of high salinity and inhibitory compounds in the investigated leachate. The process was characterised by very low sludge production (lower than 0.02 kg TSS/kg CODremoved).

Laboratory scale investigation has been carried out for the optimization of a new process for separation and recovery of Pb/Fe species from automobile battery manufacturing wastewaters. The innovation, based on ion exchange, allows for separation and recovery of the mentioned species by the use of a commercial weak anion resin (Duolite A7 from Rohm&Haas Co, USA), as selective sorbent for the ferric species, and a weak cation resin with carboxylate functionality (Purolite C106 from Purolite Co.,UK) for removal and recovery of lead species. Cl-form anion resin was eluted with real automobile battery wastewaters (pH 3; F-es= 4BV/h; influent Fe concentration: 2 mg/L) for a column throughput exceeding 200 BV (Bed Volumes) with Fe leakage steadily below 0.2 mg/L, (ten times lower the maximum allowable concentration, MAC, for discharge in closed water bodies, enforced by EU legislation). Lead species were removed and recovered on Na/H-form cation resin (pH 6; F-exh=20 BV/h; influent Pb concentration: 4 mg/L) for a column throughput exceeding 15,000 BV at average Pb leakage below 0.03 mg/L (MAC=0.2 mgPb/L). Both sorbents were regenerated by limited amounts of 1M HCl. Specifically, resin Duolite A7 was eluted with 5 BV (F-reg=2BV/h), and carboxylate resin was eluted with 30BV (F-reg=10BV/h). Recovery of metal species from resin spent regeneration eluates may be obtained by neutralization and quantitative precipitation of hydroxycerussite [basic lead carbonate, (Pb-3(OH)(2)(CO3)(2)], ready for reuse in the same battery industry and/or other productive activities. Ferric chloride in the resin spent regeneration eluate was directly recycled as coagulant to the wastewater treatment operations.

Sorption properties of olive husk were investigated under equilibrium (batch tests) and dynamic (column tests) conditions in order to assess the possibility of using such a waste material for removing heavy metals from aqueous streams. Husk samples were contacted, at 25°C, with aqueous solutions of nitric salts of Pb, Cd, Cu, and Zn. Sorption isotherms obtained from equilibrium data were fitted and interpreted by the Freundlich model. Metals-saturated husk samples resulting from column tests were air-dried and incinerated to simulate combustion in order to assess the fate of sorbed metals. The results demonstrated that, under both equilibrium and dynamic conditions, metal sorption capacity of the husk was in the sequence Pb>Cd>Cu>Zn. For all the metals, calculated Freundlich constants decreased by increasing initial metal concentration or decreasing solution pH. In dynamic tests, a significant reduction of sorption capacity was recorded (except for copper) when a metal was fed simultaneously to the others: Pb (77%); Cd (93%); Zn (68%). Combustion tests carried out on metals-saturated husk samples showed that the average losses of lead and cadmium, as volatile species, were always three to four times greater than the losses of copper and zinc, in both single-metal- and multimetal-saturated samples.

Sorption properties of olive husk were investigated under equilibrium (batch tests) and dynamic (column tests) conditions in order to assess the possibility of using such a waste material for removing heavy metals from aqueous streams. Husk samples were contacted, at 25 degrees C, with aqueous solutions of nitric salts of Pb, Cd, Cu, and Zn. Sorption isotherms obtained from equilibrium data were fitted and interpreted by the Freundlich model. Metals-saturated husk samples resulting from column tests were air-dried and incinerated to simulate combustion in order to assess the fate of sorbed metals. The results demonstrated that, under both equilibrium and dynamic conditions, metal sorption capacity of the husk was in the sequence Pb>Cd>Cu>Zn. For all the metals, calculated Freundlich constants decreased by increasing initial metal concentration or decreasing solution pH. In dynamic tests, a significant reduction of sorption capacity was recorded (except for copper) when a metal was fed simultaneously to the others: Pb (77%); Cd (93%); Zn (68%). Combustion tests carried out on metals-saturated husk samples showed that the average losses of lead and cadmium, as volatile species, were always three to four times greater than the losses of copper and zinc, in both single-metal- and multimetal-saturated samples.

The aim of this study was to check the effectiveness of the Fenton’s reagent (Fe2++H2O2+H+) for the pre-treatment of a municipal landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD5/COD ratio, up to a value compatible with biological treatment. The leachate came from a municipal sanitary landfill located in southern Italy and the average values of its main parameters were: pH=8.2; COD=10540 mgl−1; BOD5=2300 mgl−1; TOC=3900 mgl−1; NH4-N=5210 mgl−1; conductivity=45350 μScm−1; alkalinity=21470 mgl−1 CaCO3. The effect of initial pH value on the pre-treatment effectiveness was evaluated by titrating the amount of acidic by-products formed. The extent of leachate oxidation was monitored and controlled by both pH and redox potential measurements. The best operational conditions for achieving the desired goal (i.e., BOD5/COD⩾0.5) resulted: Fe2+=275 mgl−1; H2O2=3300 mgl−1; initial pH=3; reaction time=2 h. At the end of the Fenton’s pre-treatment, in order to permit a subsequent biological treatment, residual ferric ions were removed increasing the pH up to 8.5 by adding 3 gl−1 of Ca(OH)2 and 3 mgl−1 of a cationic polyelectrolyte, the latter as an aid to coagulation. This final step also resulted in a further modest removal of residual COD due to co-precipitation phenomena.

Treatment, removal and recovery of lead (3 mg/L) from battery industry wastewaters have been investigated utilising a chemical precipitation process with soluble starch xanthate (SX) at pH 5-6. A reactant ratio, i.e., SX/Pb(II) = 6 mol/mol, a reaction time of 15 min., the addition of 15 mg/L of a cationic polyelectrolyte and a final filtration gave residual lead concentrations in the liquid phase less than 0.2 mg/L, well below the maximum limit established by the EU Directive. Lead was extracted from the obtained sludge by oxidation with sodium hypochlorite or hydrogen peroxide solutions. The amounts of oxidant needed were quantified as 13.5 mol NaClO/mol Pb and one order of magnitude larger, for H2O2, the latter due to the competitive disproportion reaction of the oxidant. The metal extraction was quantitative using sodium hypochlorite; when hydrogen peroxide was used, the formation of insoluble PbSO4 (Anglesite) gave a 80% metal extraction. In both cases molar ratios between sulphate and lead ions in the extracted solutions were in the range 2.1-2.2, in agreement with the stoichiometries of the reactions. Lead can be quantitatively recovered from the extracted (NaClO) solutions, for reuse, after a chemical precipitation process with 1M NaOH at pH 9-9.5, in the form of hydrocerussite [Pb3(CO3)2(OH)2].

Technical feasibility of an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated. In absence of aluminium and ferric species, lead is quantitatively removed and recovered (approximate to 90%) from the neutralised wastewaters after elution on the natural zeolite clinoptilolite. Control of pH to 5.5-6 is necessary to minimise degradation of the exchanger material. Throughput volumes exceeding 2,700 bed volumes (BV) (flowrate: F-exh= 10 BV/h) is obtained, when the initial Pb concentration is 4 mg/L, with the metal leakage steadily below the maximum allowable concentration (MAC<0.2 mgPb/L) set by the EU for discharge in rivers, lakes, coastal seawater. Regeneration of the zeolite is carried out by controlled elution of limited amounts of 1M NaCl, pH 4.5 (40BV, F-reg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recovered to the battery manufacturing operations. This latter operation is carried-out by precipitation in the form of hydroxycerussite (basic lead carbonate) or electrolysis as pure metal. In this way it is minimized the environmental impact after waste disposal (no hazardous waste formation) and, at the same time, it is recovered raw materials to the productive lines of origin (environmental protection and resource conservation). The exhausted mother liquors from lead precipitation operation is recycled to the subsequent zeolite regeneration step, after back-up of the initial regenerant concentration and solution pH.

Lead precipitation tests from aqueous solutions containing 10 mg 1−1 Pb and 10−2 M sulphate were performed in the pH range 3.9–11.3, at inorganic carbon concentrations from background levels (≈ 3 × 10−5 M) to 1.5 × 10−2 M. Filterable lead and inorganic carbon concentrations, pH, and X-ray diffraction of the precipitate were measured during long-term ageing of precipitate suspensions in sealed bottles. Even though CO2 exchange with the atmosphere could not be completely prevented in the experimental procedure used, quasi equilibrium conditions between soluble and solid phases were achieved a few hours or days after reagents blending. Residual filterable lead concentrations ⩾ 0.1 mg 1−1 were obtained in the aged precipitate suspensions. A satisfactory agreement between solubility predictions by the equilibrium speciation model MINTEQA2 and filterable lead concentrations measured in aged samples may be obtained only with a critical selection of the solid phases considered in the speciation model. X-ray diffraction analysis showed the formation of three different solids: anglesite (PbSO4(s)), cerussite (PbCO3(s)), and hydrocerussite (Pb3(CO3)2(OH)2(s)). Other solid phases, even though stable from a thermodynamic point of view, seem to be hindered by kinetic limitations from precipitating at room temperature, and are not appropriate solid phases in modelling lead precipitation from aqueous solutions. The results of this work may be useful in predicting maximum achievable efficiencies in the neutralization/precipitation treatment of lead-bearing wastewaters.

The process of neutralization with NaOH, in the presence of Fe(III) salt, of sulphuric acid battery industry wastewater seems to be more suitable than any other process for Pb removal because at the same time, it allows the exploitation of the scavenger action of Fe(III), which is often present in the same wastewater and precipitates as hydroxides. In order to optimize sludge production, a laboratory research study has been carried out to minimize the quantity of Fe(III) to be added. All aspects concerning the chemistry of wastewater have been taken into consideration step by step and discussed. As a result, a process which requires the addition of Fe(III) so that an Fe/Pb ratio, both expressed as ppm, of the order of 0.5 is achieved. The process has been applied to two artificial solutions, characterized by a content of H2SO4 of 1000 and 5000 ppm, respectively, and by 10 ppm of Pb, as well as to five samples of wastewater. The proposed process takes about 1 h to perform: 30 min for neutralization up to pH 8.5–9.5 and Fe(III) addition and 30 min for correction in the 9–9.5 pH range and for flocculation with the help of a polyelectrolyte. The Pb concentration of the treated effluent is below 0.2 ppm. Conditions for Pb removal using only NaOH or Na2CO3 have also been considered.