Optimum Removal Efficiency Research Articles

Biosorption performance of date palm empty fruit bunch wastes for toxic hexavalent chromium removal

Biosorption ability of date palm empty fruit bunch (DPEFB) was examined for the removal of toxic hexavalent chromium (Cr6+) ions from synthetic wastewater. The pretreated DPEFB biosorbent was studied for its morphology and surface chemistry through Scanning electron microscopy, Energy dispersive elemental analysis and Fourier transform infrared spectroscopy. Effect of biosorption parameters such as pH, biosorbent dosage, contact time, temperature, initial feed concentration and agitation speed on the Cr6+ ions removal efficiency by DPEFB was critically evaluated. The isoelectric point for the DPEFB sorbent was observed at pH 2, above which it was dehydronated to capture the positively charged Cr6+ ions. Batch biosorption studies showed that an optimal chromium removal efficiency of 58.02% was recorded by the DPEFB biosorbent for pH 2, dosage 0.3 g, 100 rpm agitation speed, 120 min contact time, 50 mg/L initial feed concentration and 30 °C operational temperature. Thermodynamic analysis showed that the binding of Cr6+ ions on DPEFB surface was exothermic, stable and favorable at room temperature. Equilibrium behavior of chromium binding on DPEFB was more aligned to Temkin isotherm (R2 = 0.9852) highlighting the indirect interactions between Cr6+ ions and the biosorbent. Kinetic modeling revealed that the biosorption of Cr6+ ions by DPEFB obeyed pseudo-second order model than the pseudo-first order and intra-particle diffusion models. Reusability studies of the DPEFB sorbent showed that NaNO3 was an effective regenerant and the biosorbent can be efficiently reused up to three successive biosorption-desorption cycles for chromium removal. In summary, the results clearly showed that the DPEFB biowaste seems to be an efficient, economic and eco-friendly biosorbent for sustainable removal of toxic hexavalent chromium ions from domestic and industrial wastewater streams.

APPLICABILITY OF USING REVERSE OSMOSIS MEMBRANE TECHNOLOGY FOR WASTEWATER RECLAMATION IN THE GAZA STRIP

Reverse osmosis (RO) technology shows common popularity in the field of water treatment as an advanced stage to eliminate the residual biogenic elements and dissolved impurities after the traditional treatment processes. This article highlights the applicability of using RO membrane technology as a post-treatment stage to treat the discharged effluent from the Gaza wastewater treatment plant. The designed experimental model reveals optimal removal efficiency between 92 and 100% for a number of physical, chemical and biological pollutants. The RO membrane unit demonstrates significant removal efficiency compared to the sand filter where the RO removal efficiency for BOD, TSS, TDS, Fecal Coliform and NO3 were 100, 97.5, 92, 100 and 100%, respectively. The quality of reclaimed wastewater was idealistic where the contents of BOD, Fecal Coliform and NO3 in the permeate were nil, and the concentrations of TDS and TSS were 20 and 296 ppm, respectively. Practically, the results confirm that the wastewater with the reclaimed quality could be used for agricultural activities with no degree of restriction according to FAO’s guidelines water quality for irrigation. According to the Palestinian Standard (PS), the quality of reclaimed wastewater is high, class (A), and it could be used without restrictions to irrigate many crops and for the purposes of groundwater replenishment. Related to energy estimation and cost analysis, the numerical model and the market analysis study demonstrate the energy of 1.23 kWh and total cost, i.e. fixed and energy costs, of 0.58 USD to produce 1 m3 of reclaimed wastewater using the RO membrane in the Gaza Strip over a projected lifespan of 5 years.

Removal of harmful algal blooms in freshwater by buoyant-bead flotation using chitosan-coated fly ash cenospheres.

Harmful algal blooms (HABs) are a growing problem worldwide, damaging human and ecosystem health. In this study, a novel buoyant-bead flotation (BBF) method using chitosan-coated fly ash cenospheres (CFACs) was developed to remove HABs in freshwater. To achieve a high removal efficiency of harmful algae (Chlorella vulgaris, Scenedesmus quadricauda, and Microcystis aeruginosa), this study investigated the effects of chitosan/fly ash ratios in CFAC composite, CFAC concentration, flotation time, and pH values on the microalgae removal. The optimized ratio of CFACs is 0.1:12, and the optimized CFAC concentration is 0.3-0.7gL-1. However, the lower or higher ratios (0.1:4, 0.1:8, 0.1:16) result in microalgae reaching a zero-point charge too late or early, which failed to effectively remove HABs with an appropriate coal fly ash dosage. An optimized removal efficiency of 98.50% for Microcystis aeruginosa was reached at pH of 6.0. The optimized efficiency of Scenedesmus quadricauda and Chlorella vulgaris was 99.37% and 91.63%, respectively, at pH of 8.0. At neutral pH conditions, the surface charge of microalgae cells and CFACs are different, promoting aggregate formation. When CFACs were used to remove microalgae, aggregate size significantly influenced removal efficiency. Meanwhile, at the optimized pH and concentration, the removal efficiency of all three algal species exceeded 90.00% in 5min. The study highlights an efficient and inexpensive method for removing HABs and obtains the optimized operational conditions.

Electron buffer formation through coupling thiosulfate-dependent denitratation with anammox in a single-stage sequencing batch reactor

The combination of thiosulfate-dependent denitratation and anammox in a single-stage reactor provides a feasible way to improve total nitrogen removal. The molar ratios of NH4+/NO3− and S2O32−/NO3− were confirmed to be two key factors affecting the reactor performance. The optimal total nitrogen removal efficiency of 99.4% was achieved at NH4+/NO3− of 0.75 and S2O32−/NO3− of 0.85. The multiple thiosulfate oxidation pathways contribute to electron buffers generated in the system. A novel isotope labeling method using 15N was applied to reveal N transformation pathways and a 3-step model was proposed. The nitrate was first converted to nitrite or nitric oxide (NO) by sulfur-oxidizing bacteria. In the second step, both nitrite and NO were utilized by anammox bacteria. Finally, the nitrate generated from anammox could be removed using sulfur deposits as electron donors. The findings provide a potential solution for mainstream nitrogen removal.

Treatment of Landfill Leachate Using Palm Oil Mill Effluent

Sanitary landfilling is the most common method of removing urban solid waste in developing countries. Landfills contain high levels of organic materials, ammonia, and heavy metals, thereby producing leachate which causes a possible future pollution of ground and surface water. Recently, agricultural waste was considered a co-substratum to promote the biodegradation of organics in industrial wastewater. The use of low-cost and natural materials for wastewater treatment is now being considered by many researchers. In this study, palm oil mill effluent (POME) was used for treating stabilized leachate from old landfill. A set of preliminary experiments using different POME/leachate ratios and aeration times was performed to identify the setting of experimental design and optimize the effect of employing POME on four responses: chemical oxygen demand (COD), total suspended solids (TSS), color, and ammoniacal nitrogen (NH3-N). The treatment efficiency was evaluated based on the removal of four selected (responses) parameters. The optimum removal efficiency for COD, TSS, color, and NH3-N was 87.15%, 65.54%, 52.78%, and 91.75%, respectively, using a POME/leachate mixing ratio of 188.32 mL/811.68 mL and 21 days of aeration time. The results demonstrate that POME-based agricultural waste can be effectively employed for organic removal from leachate.

Correlation Study on Operation of the Wet FGD System and Incomplete Coal Combustion

A Wet Flue Gas Desulfurization (WFGD) system operating at thermal power plant Rovinari (Romania), was considered in this study in an attempt to establish mutual or uni-directional influences between the performance of the sulphur removal process and the quality of the combustion process. Although in theory the WFGD system operates automatically with parameters controlled in such way that optimum removal efficiency is obtained, some parameters cannot be fully controlled, especially those that could not be anticipated at the design of the WFGD system. Sulphur removal systems are customizable to some extent but cannot provide an optimum solution for any plant, given the large range of differences between various plants. Coal quality is such a parameter, for which a large range of values and high standard deviation exists. Incomplete combustion is a serious issue caused by low coal quality resulting in significant losses. Briefly, incomplete combustion process is equivalent to coal that is injected in the furnace but does not undergo combustion or undergoes a partial combustion, being eventually evacuated from the boiler. This study attempts to identify quantitative and qualitative influence of incomplete combustion on the operation of the FGD system

Manganese removal efficiencies and bacterial community profiles in non-bioaugmented and in bioaugmented sand filters exposed to different temperatures

Biological sand filtration systems are widely used to remove Manganese (Mn) from groundwater. Different experiences have demonstrated that low environmental temperatures decrease the performance of these systems. In order to overcome this problem, in a previous work, a Pseudomonas sagittaria strain named MOB-181, that showed high Mn(II) oxidation and biofilm formation capacities when grown at low temperatures, was isolated. Here, the impact of summer and winter temperatures on Mn removal efficiencies and on bacterial community profiles of both, non-bioaugmented and MOB-181 bioaugmented sand filters, was analyzed. Under summer conditions, MOB-181 inoculated columns showed the best Mn removal performance, removing Mn from the first day of system operation with an efficiency of 27%; also these columns reached an optimum Mn removal efficiency (95%) earlier than control columns (23 days and 29 days, respectively). Under winter conditions, the 27% efficiency was reached earlier for the inoculated columns than for control columns (20 days and 42 days, respectively); and the maximum efficiency (95%) was also reached faster than for the controls (39 days and 54 days, respectively). Bacterial communities profiles were more influenced by temperature changes than by the bioaugmentation process. This work demonstrated the importance of bioaugmentation with the MOB-181 strain to improve Mn removal, by shortening start-up periods, mainly at lower temperatures. Moreover, the obtained data will improve the knowledge on bacterial communities ecosystem involved in Mn removal at different temperatures and should help in developing novel bioaugmentation strategies for the optimization of biological groundwater treatment plants.

Application of response surface methodology for optimization of zinc elimination from a polluted soil using tartaric acid

Heavy metal wastes generated from mining activities are a major concern in developing countries such as Iran. Increasing concentrations of these metals in the soil make up a severe health hazard due to their non-degradability and toxicity. In this study, batch washing experiments were conducted in order to investigate the removal efficiency of zinc by biodegradable chelates, tartaric acid. For this purpose, soil samples were collected from the zinc contaminated soil in the region of the Angouran, Zanjan, Iran. Hence, optimization of batch washing conditions followed using a three-level central composite design approach based on the response surface methodology. The results demonstrated that the effects of pH, tartaric acid concentration, and interaction between selective factors on the zinc removal efficiency were all positive and significant (P < 0.05). An optimum zinc removal efficiency of 89.35 ±2.12% was achieved at tartaric acid concentration of 200 mM l−1, pH of 4.46, and incubation time of 120 min as the optimal conditions. Accordingly, response surface methodology is appropriately capable to determine and optimize chemical soil washing process to remediate heavy metal polluted soil.

Facile Ge/GR nanocubes synthesis and application for Sudan I photodegradation in water

In this work, highly uniform cubic germanium/husk-derived graphene nanocomposites (Ge/GR nanocubes) were synthesized via facile chemical methods. The structure and composition of the prepared Ge/GR nanocubes were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) etc., confirming a homogeneous distribution of Ge nanocubes (30–90 nm in size) on few-layered graphene nanosheets. Further investigations showed that the prepared novel Ge/GR nanocubes could combine both photocatalytical advantages of Ge nanocubes and graphene nanosheets for Sudan I purification with optimal removal efficiency of 98.1% in wide concentration range (0.25–4.0 mg/mL) at mild conditions. The prepared high active photocatalyst can be used for five consecutive runs. By using husk-derived graphite microcrystalline as the starting material of graphene, the cost of the Ge/GR nanocubes was obvious decreased, which fosters it a high active, low cost and durable candidate for azo dye removal in water.

Construction and Denitrification Performance of A2/O Based on Partial Nitrification Coupled with an ANAMMOX System

To resolve the issue of existing municipal wastewater treatment plants (WWTPs) in China with an insufficient influent carbon source, a bench-scale A2/O process based on partial nitrification coupled with ANAMMOX was constructed by controlling aeration partition ratio, dissolved oxygen (DO) concentration, and sludge retention time (SRT). In this study, the nitrogen removal performance, nitrogen removal pathway, and microbial community structure of the system under different conditions were investigated. The results showed that the system had excellent nitrogen removal efficiency at low-C/N influent (C/N=5). The A2/O reactor had experienced the co-culture stage (Phase 1), screening stage (Phase 2-3), and enrichment stage (Phase 4) successively during the 140-day experiment, and the nitrogen removal pathway changed from nitrification and denitrification to partial nitrification coupled ANAMMOX in the end. The optimal removal efficiencies of 97.69% for NH4+-N and 87.83% for TN were obtained in the enrichment stage (Phase 4), and the effluent concentration of NH4+-N and TN were 1.20 mg·L-1 and 7.03 mg·L-1, respectively. Illumina MiSeq sequencing results showed that the enrichment of AOB including Nitrosomonas and Nitrosospira and the elimination of NOB including Nitrospira, Nitrococcus, and Nitrobacter were the main causes of achieving partial nitrification in the system. The enrichment of AnAOB including Candidatus Kuenenia and Candidatus Jettenia was the key point for the occurrence of ANAMMOX in the system, and thus, played an important role in the achievement of advanced nitrogen removal.

Electrochemical Treatment of Cattle Wastewater Samples

Cattle wastewater (CWW) is considered an important source of contamination in the livestock sector. Therefore, electrocoagulation (EC) using Aluminium electrodes and electrooxidation (EO) through Boron Doped Diamond (BDD) electrodes processes, were applied to the liquid fraction of cattle waste (CW) to decrease the levels of certain pollutants such as nitrogen (N-NO3, T-N), phosphates (P-PO4) and organic content (Chemical Oxygen Demand, COD), in order to eliminate their environmental impacts to soil, groundwater and atmosphere. The respective electrochemical methods, were compared with chemical coagulation process by using Al2(SO4)3 and FeCl3 as a coagulant. CWW samples were derived from three cattle farms. As experimentally was revealed, the main parameters strongly affecting the experimental procedure were the solid density of the sample and the high concentration of pollutants. Other operating parameters such as current density, electroprocessing time, dilution ratio and agitation speed were studied and optimised. Results showed an optimal removal efficiency after using the combined EC-EO processes at current density of 200A/m2, agitation at 300 rpm, duration time of 2 h for both processes at room temperature, with a 1:5 dilution ratio. The results also showed that P-PO4 were fully removed, COD up to 70%, N-NO3 at 80% and T-N close to 20%. The combined use of EC and EO improved the quality of CWW in regard to P-PO4, COD, N-NO3 and T-N content. Nevertheless, further experiments are needed in order to verify the respective results in a pilot scale.

Experimental Study on Chloride Ion Removal in High-Salt Wastewater System

Chlorine is usually present in the environment in an ionic state, is highly mobile and difficult to degrade. High-chlorine wastewater can corrode buildings and affect the growth of animals and plants. Therefore, how to solve the environmental problem of high concentration of chloride ions well and effectively has drawn the intensive attention of the society. In this paper, chloride ion is removed from wastewater with the method of coprous chloride precipitation, and investigation is made on the effects of pH, temperature, amount of precipitant, titration time and reaction time on the removal efficiency of chloride ions. The results show that: when nCuSO4:nNa2SO3:nNaCl: n(ascorbic acid) =1.3:1.1:1: 0.01, and reaction pH is 3, temperature is 80 °C, titration time of sodium sulfite is 20min, reaction time after titration is 30min, the chloride ion has the optimal removal efficiency. SEM method is used for the characterization of the precipitates formed by the reaction. The results show that the experimentally produced complex cuprous chloride is irregular polyhedron with uneven particle size.

Olive mill wastewater treatment using infiltration percolation in column followed by aerobic biological treatment

This work aims to treat olive mill wastewater (OMWW) by infiltration percolation in different columns containing filtration sand, granular activated carbon, and lime, and thus followed by biological treatment using the soil microorganisms to the treatment that will give the best results. The optimum removal efficiency was obtained using granular activated carbon column mixed with 15% of lime with percentages removal of 39.33, 60.28, 53.17 and 88.74% for biological oxygen demand (BOD5), chemical oxygen demand (COD), polyphenols and suspended matter respectively. Aerobic treatment 30 days of OMWW obtained from the column of activated carbon mixed with 15% of lime, neutralized and diluted 15 times with distilled water was investigated. The results showed a significant percentage reduction of 79.78, 69.43, and 60.67%, respectively, for BOD5, COD, and polyphenols. The global removal percentages after the two successive treatments were 87.86% for COD, 87.39% for BOD5 and 81.59% for polyphenols compounds. Fourier Transformed Infrared spectroscopy analysis of crude OMWW, infiltrated percolated and biologically treated, showed a difference between the spectra that manifests by the reduction of the spectrum intensity bands after each treatment stage, which confirmed the analytical results. Soil microorganisms have shown their biodegradation efficiency of organic matter and polyphenols of these much-polluted effluents under aerobic conditions. The results indicated that the pretreatment of raw olive mill wastewater could be realized before biological treatment to obtain a satisfactory reduction.

Synthesis of Magnetic Gluten/Pectin/Fe3O4 Nano-hydrogel and Its Use to Reduce Environmental Pollutants from Lake Urmia Sediments

The aim of this study was to synthesize Fe3O4 nanoparticles and gluten/pectin/Fe3O4 composite hydrogel. This nano-hydrogel was then used to reduce sediment contamination in Lake Urmia (Iran). For this purpose, magnetic nanoparticles were chemically synthesized. Two types of composite Hydrogels including gluten/Fe3O4 and gluten/pectin/Fe3O4 composites were prepared by adding Fe3O4 nanoparticles and pectin to wheat gluten. The properties of Hydrogels were studied by scanning electron microscopy (SEM), Fourier-transform infrared and X-ray diffraction methods. SEM results showed that Fe3O4 particles were seed shape (30–60 nm). The results confirmed the physical interactions between magnetic nanoparticles, pectin and gluten. Subsequently, the prepared Hydrogels were used to reduce the pollution of Lake Urmia sediments. Central composite design was used to investigate the effect of interaction time and interaction temperature of hydrogel with sediment and the type of hydrogel. Qualitative characteristics of the sediments, including heavy metal concentrations (arsenic, barium, cadmium, lead, mercury and chromium), biochemical oxygen demand, and chemical oxygen demand COD, and organic compounds were investigated before and after treatment of sediments with hydrogel. The effect of hydrogel on enhancing sediment quality was investigated. The results showed that in the optimum condition removal efficiency of total heavy metals was 62% and removal efficiency of total organic compounds was 42%. The results also showed that gluten/pectin/Fe3O4 hydrogel had better performance in reducing environmental pollutants of sediment than wheat gluten/Fe3O4 hydrogel.

In-situ debromination mechanism based on self-activation and catalysis of Ca(OH)2 during pyrolysis of waste printed circuit boards

Completely and deeply removed bromide from waste printed circuit boards (WPCBs) is necessary due to their toxicity and carcinogenicity. To achieve this purpose, calcium hydroxide (Ca(OH)2) as a debromination agent was added during pyrolysis process of WPCBs. The results showed that hydrogen bromide (HBr), 4-bromophenol, 2-bromophenol and 2,4-dibromophenol were the main bromide species in pyrolysis products. The Ca(OH)2 plays a significant role for removing HBr and organic bromide, but not affects products yield. Optimal removal efficiency for 4-bromophenol, 2-bromophenol and 2,4-dibromophenol reached 87.5 %, 74.6 % and 54.5 %, respectively. And debromination efficiency was related to the steric hindrance caused by bromide atoms. The Ca(OH)2 can be activated by captured HBr and its thermal decomposition. And the newly-generated calcium bromide and calcium oxide significantly facilitate debromination due to their high surface energy and reactivity. The debromination mechanism was clarified by experiments coupled with computational chemistry: the coordination of bromide and calcium to form [Ph-Br···Ca2+] or [Ph-Br···Caatom]. Then, electrons were delivered form bromide atom to Ca2+ or Caatom, which resulted in the stretch and weaken the C-Br bond. Hence, the C-Br bond was more easily to break. This work can provide support for designing novel and efficient debromination agents applied for high-temperature system.

Effect of nanobubbles for improvement of water quality in freshwater: Flotation model simulation

Recently, nanobubbles (NBs) in flotation have been discussed as a highly promising technique for separation or remediation of water contaminants in the environmental field. This study performed model simulations using a flotation model (FM) with NBs and very highly hydrophobic small particles, such as sediments of freshwater containing inorganic particles (clay and silt) and plastic debris. This study examined and confirmed that the effect of NBs for remediation of particles depends on the size and number of bubbles, size and density of aggregates, time of aggregate formation, and so on. This study also confirmed the NBs’ features, such as the adjustment of their surface charge in electrolyte solutions as well as their affinity for hydrophobic surfaces leading to their stability. The features affect the attachment efficiency, which is estimated by calculating the surface interaction forces of hydrodynamics and surface chemistry. The aggregates formed by the attached NBs obtained very high formation efficiency (X) due to their very high attachment efficiency but very low separation efficiency (Y) due to their very slow rising velocity. In conclusion, the NBs may deteriorate the water quality instead of improving it because the aggregates formed by the NBs stay in the suspension for a long stagnation time. Therefore, further research is required to discover a more reasonable method for applying NBs with MBs in the field of freshwater treatment that causes a minimal adverse effect on the ecosystem and helps in optimal removal efficiency of the hydrophobic fine particles.

Treatment of real printing wastewater using electrocoagulation process with titanium and zinc electrodes

Electrocoagulation (EC) has numerous benefits over traditional coagulation. It is noteworthy that most researchers have studied EC using either iron electrodes or aluminum electrodes. The key objective of this study is to investigate the performance of the EC process with zinc and titanium electrodes for treating real printing wastewater through several experimental conditions. Experiments were done through batch systems. The effects of the operating variables, inclusive of varying current densities (CDs), spacing between electrodes, electrolysis time, and varying electrode materials (titanium and zinc) on the efficiency of the removal of different parameters were studied. Oil and grease, total dissolved solids (TDS), and chemical oxygen demand (COD) were among these parameters. The highest removal efficiency for COD after 90 min using a zinc electrode was approximately 50 % attained at 20 mA/cm2. For the titanium electrode, after 90 min, the highest removal efficiency for COD was 46 % attained at 15 mA/cm2. For the removal efficiency of TDS, the zinc electrode performance was better than that of the titanium electrode for every CD. After 90 min, the optimal TDS removal efficiencies were 9 % and 19 % for titanium and zinc electrodes, respectively. The titanium electrode offers the maximum efficiency of removal for oil and grease. The highest efficiencies of removal were attained at a separation distance of 4 cm. At a CD of 15 mA/cm2, the best COD elimination efficiencies using the titanium electrode at the separation distances of 6, 4, and 2 cm were 24 %, 47 %, and 30 %, respectively. At a CD of 15 mA/cm2, the best COD removal efficiencies using the zinc electrode at the separation distances of 6, 4, and 2 cm were 27 %, 41 %, and 38 %, respectively. In both the zinc and titanium electrodes, following the experiments, corrosion occurred in the anodes, which is evidence that the process of treatment took place. The EC performance was observed to be much better than that of conventional coagulation during the treatment of printing wastewater. Zinc and titanium electrodes demonstrated a good capability of removing pollutants when used in the EC process.

Removal of sarafloxacin from aqueous solution by a magnetized metal-organic framework; Artificial neural network modeling

Antibiotics are one of the pollutants that their existence in the environment which causes serious problems. The residual of these compounds in the environment has negative influences on human health, and hence, their removal from the environment is a vital task.In this study, the removal of sarafloxacin (SRF) has performed using a magnetized metal-organic framework (Fe3O4/MIL-101(Fe)). Response surface methodology (RSM) was employed to achieve optimized removal efficiency. The optimized removal efficiency of SRF was obtained under the following conditions: the SRF initial concentration 10 ppm, pH value of 7.0, the adsorbent dosage of 20 mg, and the contact time of 40 min. The isotherm models were also investigated. The Langmuir isotherm model (type II) was more consistency in the adsorption process. The artificial neural network (ANN) as a predictive model was applied to predicting the SRF removal efficiency from aqueous solution. The algorithm of Levenberg-Marquardt was used for the training of the ANN. The performance of the model was evaluated based on the coefficient of determination (R2) and mean squared error (MSE). The values of R2 (R2 = 0.9995, 0.9951) and MSE (MSE = 3.98e−05, 0.0023) were for training and testing data set, respectively. Results showed a good agreement between experimental and predicted data obtained by the ANN model as a powerful tool for prediction removal percentage of SRF (Rpred2 = 0.9861).

Color removal efficiency of rice husk biochar modified with magnetized iron oxides and nano zero valent iron for decolorization of dyeing wastewater

Rice husk biochar, a rich-carbon material, can be modified with other reactive elements to improve its original properties for organic-contaminant removal efficiency. In this study, rice husk was heated to 600 oC without air in a closed-furnace for producing the rice husk biochar (BC600). BC600 was then magnetized for making an intermediate magnetized rice husk biochar (BC600-mag). Finally, nano zero valent iron (nZVI) was synthesized on BC600-mag for producing magnetized biochar impregnated nZVI (BC600-mag-nZVI). Batch experiments were conducted to investigate color removal efficiency of BC600-mag-nZVI for the reactive dyes yellow (RY145), red (RR195) and blue (RB19) from dyeing solutions with the initial color concentrations of approximately 400 Pt-Co. Results showed that, for RY145 and RR195, the optimum color removal efficiency (ɳopt) achieved the values of 95 and 93% at doses of 0.50 and 1.50 kg BC600-mag-nZVI/m3 dyeing solution, according to the treated color decreased to 21 and 30 Pt-Co, respectively, which are lower than the allowable discharged standard of column A (≤ 50 Pt-Co) of QCVN 40:2011/BTNMT, while for RB19, the ɳopt achieved the values of 63 % at dose of 8.00 kg BC600-mag-nZVI/m3 dyeing solution, according to the treated color decreased to 147 Pt-Co which is lower than the allowable discharged standard of column B (≤ 150 Pt-Co) of QCVN 40:2011/BTNMT. In addition, with increasing dose of the modified biochars, the color removal efficiency increased accordingly, achieving almost 100% for RY145 and RR195 and over 70% for RB19. It is concluded that the magnetic-nZVI rice husk biochars effectively removed the reactive dyes. In the other hand, the impregnation of nZVI particles on the biochar backbone spatially separates the particles, prevents their aggregation and therefore enhances their reactivity This study therefore proposes a new application of rice husk biochar modified with magnetized iron oxides and zero valent iron decolorization of dyeing wastewater.

Investigation of biodegradable polyaspartate as an effective chelant for washing of lead from soil: response surface methodology approach

ABSTRACT In this work, a biodegradable chelant (polyaspartate) was synthesised by using L-aspartic via polysuccinimide and used for removal of lead from polluted soil. The interactive effects of operating parameters, polyaspartate dose, metal concentration, polyaspartate/soil ratio, pH and extraction time, were examined via 35 factorial face-centred central composite design matrix and response surface methodology. The examined responses for the two models developed were (i) concentration of extracted Pb in polyaspartate solution and (ii) residual concentration of Pb in the treated soil. The optimal removal efficiency was 90%, which yields 18 mg/L of extracted Pb and 50 mg/kg of residual Pb in the treated soil, at conditions of pH 3, extraction time of 6 h under highest level of initial Pb concentration (500 mg/kg), polymer/soil ratio of 25 and polyaspartate dose of 36 mmol/L. However, at the lowest level of polymer/soil ratio of 5, the maximum removal efficiency dwindled to 59% with higher residual Pb and extracted Pb concentrations of 205 mg/kg and 59 mg/L, respectively. The results showed that higher soil washing efficiency was linked to lower initial pH, increase in initial lead ions concentration and polyaspartate/soil ratio. The study signifies eco-friendly polyaspartate as an efficient chelant for remediation of Pb polluted soil via washing technique.