Adsorptive removal of gallic acid from aqueous solution onto magnetic ion exchange resin.

Finding an appropriate adsorbent with high adsorption capacity, quick adsorption kinetics and easy regeneration was crucial to the removal of gallic acid (GA) from water and wastewater. Our aims were to investigate whether a magnetic ion exchange (MIEX) resin had the three merits mentioned above, and investigate the feasibility of GA adsorption on MIEX resin, and the adsorption kinetics, equilibrium, thermodynamics, regeneration and mechanism using batch tests. The uptake of GA increased with increasing GA concentration. The GA concentration influenced the time needed to reach equilibrium, but the adsorption could be completed within 120 min. Elevating temperature facilitated the GA removal. The removal percent remained above 95.0% at pH 5.0-11.0. Carbonate and bicarbonate promoted the GA removal; conversely chloride, sulfate and nitrate restrained the GA removal significantly. The adsorption kinetics could be fitted well with the pseudo second-order model, and the film diffusion governed the whole adsorption rate. The equilibrium data followed the Redlich-Peterson isotherm model. The adsorption was a spontaneous, endothermic and entropy driven process. The ion exchange dominated the removal mechanism. The spent MIEX resin was well regenerated by sodium chloride. Therefore, MIEX resin is a potential adsorbent for removing GA quickly and efficiently from water and wastewater.

Application of 3-D Fluorescence: Characterization of Natural Organic Matter in Natural Water and Water Purification Systems.

Natural organic matter (NOM) found in water sources is broadly defined as a mixture of polyfunctional organic molecules, characterized by its complex structure and paramount influence on water quality. Because the inevitable release of pollutants into aquatic environments due to an ineffective control of industrial and agricultural pollution, the evaluation of the interaction of NOM with heavy metals, nanoparticles, organic pollutants and other pollutants in the aquatic environment, has greatly increased. Three-dimensional (3-D) fluorescence has the potential to reveal the interaction mechanisms between NOM and pollutants as well as the source of NOM pollution. In water purification engineering system, the 3-D fluorescence can indicate the variations of NOM composition and gives an effective prediction of water quality as well as the underline water purification mechanisms. Inadequately treated NOM is a cause of precursors of disinfection byproducts (DBPs), posing a potential threat to human health. Effective control and measurement/evaluation of NOM have long been an important factors in the prevention of water pollution. Overall, 3-D fluorescence allows for a rapid identification of organic components thus indicating possible sources of water pollution, mechanisms of pollutant interactions, and possible DBPs formed during conventional treatment of this water. This article reviews the 3-D fluorescence characteristics of NOM in natural water and typical water purification systems. The 3-D fluorescence was effective for indicating the variabilities in NOM composition and chemistry thus providing a better understanding of NOM in natural water system and water engineering system.

Photoinitiated polymerization of cationic acrylamide in aqueous solution: synthesis, characterization, and sludge dewatering performance.

A copolymer of acrylamide (AM) with acryloyloxyethyl trimethyl ammonium chloride (DAC) as the cationic monomer was synthesized under the irradiation of high-pressure mercury lamp with 2,2-azobis(2-amidinopropane) dihydrochloride (V-50) as the photoinitiator. The compositions of the photoinduced copolymer were characterized by Fourier transform infrared spectra (FTIR), ultraviolet spectra (UV), and scanning electron microscope (SEM). The effects of 6 important factors, that is, photo-initiators concentration, monomers concentration, CO(NH2)2 (urea) concentrations, pH value, mass ratio of AM to DAC, and irradiation time on the molecular weight and dissolving time, were investigated. The optimal reaction conditions were that the photo-initiators concentration was 0.3%, monomers concentration was 30 wt.%, irradiation time was 60 min, urea concentration was 0.4%, pH value was 5.0, and mass ratio of AM to DAC was 6 : 4. Its flocculation properties were evaluated with activated sludge using jar test. The zeta potential of supernatant at different cationic monomer contents was simultaneously measured. The results demonstrated the superiority of the copolymer over the commercial polyacrylamide as a flocculant.

Coagulation performance and mechanism analysis of humic acid by using covalently bonded coagulants: effect of pH and matching mechanism of humic acid functional groups.

Conventional inorganic coagulants (Al, Fe) and Al/Fe-based covalently bonded flocculants (CAFMs) had different hydrolysis species at different pHs, which subsequently led to differences in their binding sites and complexation ability with humic acid (HA). Studying the binding sites and interactions between CAFMs, AlCl3 (Al), and FeCl3 (Fe) hydrolysates and HA molecules is critical to understanding the coagulation mechanism. The results found that CAFM 0.6, Al, and AlCl3 combined FeCl3 (Al/Fe) removed more than 90% of HA at pH 6, and CAFMs showed higher HA removal rate than that of Al, Fe, and Al/Fe under the same reaction conditions. The flocs of CAFMs contained abundant -NH2/OH as well as the large particle size, compact structure, and excellent settling performance. The hydrolyzed species of Al and Fe were predominantly Alb and Feb at pH 6, but the hydrolyzed species of CAFMs were primarily (Al + Fe)c. Moreover, the hydrolyzed species of Al and Al/Fe were found to complex with HA functional groups such as -COOH, C = O, C-H/C-C, C = C, and C-OH to form ligand bonds, while the hydrolyzed species (Al + Fe)c of CAFMs could deeply interact with HA functional groups including C-O, -COOH, C = O, C-H/C-C, C = C, and C-OH by the adsorption and sweeping.

UV-Initiated polymerization of cationic polyacrylamide: synthesis, characterization, and sludge dewatering performance.

P(AM-DAC-BA) was synthesized through copolymerization of acrylamide (AM), acryloyloxyethyl trimethyl ammonium chloride (DAC), and butylacrylate (BA) under ultraviolet (UV) initiation using response surface methodology (RSM). The influences of light intensity, illumination time, and photoinitiator concentration on the intrinsic viscosity [η] of P(AM-DAC-BA) were investigated. RSM model based on the influencing data was established for optimizing synthetic conditions. It was found that, at light intensity 1491.67 µ w·cm(-2), illumination time 117.89 min, and photoinitiator concentration 0.60‰, there was a better material performance achieved. Thus P(AM-DAC-BA) prepared under the above conditions showed excellent dewatering performance that, with 40 mg·L(-1) P(AM-DAC-BA) at pH 7, the residual turbidity of supernatant and the dry solid content were up to 38 NTU, 28.5%, respectively.

Recycling waste iron-rich algal flocs as cost-effective biochar activator for heterogeneous Fenton-like reaction towards tetracycline degradation: Important role of iron species and moderately defective structures.

Harvesting aquatic harmful algal blooms (HABs) and reusing them is a promising way for antibiotic degradation. Herein, a novel iron-rich biochar (Fe-ABC), derived from algal biomass harvested by magnetic coagulation, was successfully designed and fabricated as activator for heterogeneous Fenton-like reaction. The modification methods and pyrolysis temperatures (400-800 °C) were optimized to enhance the formation of rich iron species and moderately defective structure, yielding Fe-ABC-600 with enhanced electron transfer and H2O2 activation capability. Thus, Fe-ABC-600 exhibited superior removal efficiency (95.33%) on tetracycline (TC), where the presence of multiple iron species (Fe3+, Fe2+ and Fe4+) and moderately defective structure accelerating the Fenton-like oxidation. The concentration of leaching Fe after each reaction was all below 0.74 mg/L in five cycles, ensuring the sustained degradation. And •OH was proved to be the major radical contributing to the degradation of TC, as well as the direct electron transfer mechanism together, in which the CO acted as electron regulator and electron donor. Fe-ABC as a cost-effective catalyst has notable application potentials in TC removal from wastewater owing to its remarkable advantages of high resource utilization, enhanced catalytic property, high ecological safe, notable TC degradation efficiency, low cost and environmental-friendliness.

Biodegradability enhancement of phenolic wastewater using hydrothermal pretreatment.

A novel hydrothermal pretreatment was applied for the biochemical treatment of phenolic wastewater with high concentrations of phenolic substances. The results demonstrated that 250 °C was the reaction temperature dividing point for complete oxidation, hydrothermal gasification, and amino release from carbonaceous organics in phenolic wastewater. Before the dividing point reached, some of the large molecules were hydrolyzed into small molecules of volatile phenolic substances that were easily adsorbed by the activated sludge. After the integrated hydrothermal pretreatment and anaerobic/aeration process, the removal rate of volatile phenolswas respectively reached by 97 % and 88 % with hydrothermal temperature of 250 °C and without pretreatment. Functional microorganisms (i.e., Chloroflexi) responsible for aromatic compounds degradation were enriched, thus the dioxygenases, dehydrogenase reactions, and meta-cleavage of catechol were enhanced. This work provided an innovative approach to remove phenolic substances from phenolic wastewater, and in-depth understandings of microbial responses in biochemical systems.

Hydrochloric acid-modified fungi-microalgae biochar for adsorption of tetracycline hydrochloride: Performance and mechanism.

Novel biochar (BC) was prepared by pyrolysis using Aspergillus oryzae-Microcystis aeruginosa (AOMA) flocs as raw materials. It has been used for tetracycline hydrochloride (TC) adsorption along with acid (HBC) and alkali modification (OHBC). Compared with BC (114.5 m2 g-1) and OHBC (283.9 m2 g-1), HBC had a larger specific surface area (SBET = 338.6 m2 g-1). Meanwhile, the Elovich kinetic and Sip isotherm models adequately fit the adsorption data, and intraparticle diffusion is the controlling factor for TC adsorption diffusion on HBC. Furthermore, the thermodynamic data indicated that this adsorption was endothermic and spontaneous. The experimental results demonstrated that there are multiple interactions during the adsorption reaction process, including pore filling, H-bonds, π-π interaction, hydrophobic affinity, and van der Waals forces. In general, biochar prepared from flocs of AOMA can be used to remediate tetracycline-contaminated water, and it is of great significance in improving resource utilization.

Expression profile of CYP402C1 and its role in resistance to imidacloprid in the whitefly, Bemisia tabaci.

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a cosmopolitan insect pest causing serious damage to crop production. Cytochromes P450 (CYPs) of B. tabaci are widely known to be involved in the metabolic resistance to a variety of insecticides, continuously increasing the difficulty in controlling this pest. In this study, four P450 genes (CYP6CM1, CYP6CX1, CYP6CX3, and CYP402C1) in B. tabaci exhibited correlations with the resistance to imidacloprid. We have focused on trying to understand the function and metabolism capacity of CYP402C1. The expression profiles of CYP402C1 were examined by reverse transcription quantitative real-time PCR and fluorescence in situ hybridizations. Its role in resistance to imidacloprid was investigated by RNA interference, transgenic Drosophila melanogaster, and heterologous expression. The results showed that CYP402C1 was highly expressed in the active feeding stages of B. tabaci, such as nymphs and female adults. CYP402C1 was mainly expressed in midguts of nymphs and adults, especially in the filter chamber. Knockdown of CYP402C1 significantly decreased the resistance of B. tabaci to imidacloprid by 3.96-fold (50% lethal concentration: 186.46 versus 47.08 mg/L). Overexpression of CYP402C1 in a transgenic D. melanogaster line (Gal4 > UAS-CYP402C1) significantly increased the resistance to imidacloprid from 12.68- to 14.92-fold (129.01 and 151.80 mg/L versus 1925.14 mg/L). The heterologous expression of CYP402C1 showed a metabolism ability of imidacloprid (imidacloprid decreased by 12.51% within 2 h). This study provides new insights for CYP402C1 function in B. tabaci and will help develop new strategies in B. tabaci control and its insecticide resistance.

Enhancement of 15% calcium oxide doped nano zero-valent iron on arsenic removal from high-arsenic acid wastewater.

Nano zero-valent iron (nZVI) has a great potential for arsenic removal, but it would form aggregates easily and consume largely by H+ in the strongly acidic solution. In this work, 15%CaO doped with nZVI (15%CaO-nZVI) was successfully synthesized from a simplified ball milling mixture combined with a hydrogen reduction method, which had a high adsorption capacity for As(V) removal from high-arsenic acid wastewater. More than 97% As(V) was removed by 15%CaO-nZVI under the optimum reaction conditions of pH 1.34, initial As(V) concentration 16.21 g/L, and molar ratio of Fe/As (nFe/nAs) 2.5:1. The effluent pH solution was weakly acidic 6.72, and the secondary arsenic removal treatment reduced the solid waste and improved arsenic grade in slag from the mass fraction of 20.02% to 29.07%. Multiple mechanisms including Ca2+ enhanced effect, adsorption, reduction, and co-precipitation coexisted for As(V) removal from high-arsenic acid wastewater. Doping of CaO might lead to improving cracking channels which was benefit for electronic transmission and the confusion of atomic distribution. The in situ weak alkaline environment generated on the surface of 15%CaO-nZVI would increase the content of γ-Fe2O3/Fe3O4, which was in favor for As(V) adsorption. In addition, H+ in the strongly acidic solution could accelerate corrosion of 15%CaO-nZVI and abundant fresh and reactive iron oxides continuously generated, which would provide plenty specific reactive site and fast charge transfer and ionic mobility for arsenic removal.

Enhanced removal of aqueous Cr(VI) by the in situ iron loaded activated carbon through a facile impregnation with Fe(II) and Fe(VI) two step method: Mechanism study.

In this study, a novel in situ iron-loaded activated carbon (AFPAC) was prepared by a FeSO4/K2FeO4 impregnation and oxidation combination two-step supported on activated carbon for enhanced removal of Cr(VI) from aqueous solutions. Cr(VI) removal efficiency greatly increased by AFPAC more than 70% than that of fresh activated carbon (AC), which is due to rich iron oxides formed in situ and the synergistic effect between iron oxides and activated carbon. Cr(VI) adsorption behaviors on AFPAC under different water quality parameters were investigated. The maximum monolayer adsorption capacities for Cr(VI) by AFPAC are as high as 26.24 mg/g, 28.65 mg/g, and 32.05 mg/g at 25 °C, 35 °C and 45 °C at pH 4, respectively. Density functional theory (DFT) results showed that the adsorption energy of K2Cr2O7 on the surface of FeOOH was - 2.52 eV, which was greater than that on the surface of bare AC, and more charge transfer occurred during the adsorption of K2Cr2O7 on the surface of FeOOH, greatly promoting the formation of Cr = O-Fe. Cr(VI) removal by AFPAC included electrostatic attraction, redox reaction, coordinate complexation, and co-precipitation. Cr(VI) adsorption process on AFPAC consisted of the three reaction steps: (1) AFPAC was fast protonation and Cr2O72- would electrostatically attract to the positively charged AFPAC surface. (2) Cr2O72- was reduced into Cr2O3 by the carbons bond to the oxygen functionalities on activated carbon and the redox reaction process of FeSO4 and K2FeO4. (3) The inner-sphere complexes were formed, and adsorbed on AFPAC by iron oxides and then co-precipitation.

Characteristics and mechanisms of As(III) removal by potassium ferrate coupled with Al-based coagulants: Analysis of aluminum speciation distribution and transformation.

This study was carried out to investigate the enhanced removal of arsenite (As(III)) by potassium ferrate (K2FeO4) coupled with three Al-based coagulants, which focused innovatively on the distribution and transformation of hydrolyzed aluminum species as well as the mechanism of K2FeO4 interacted with different aluminum hydrolyzed polymers during As(III) removal. Results demonstrated that As(III) removal efficiency could be substantially elevated by K2FeO4 coupled with three Al-based coagulants treatment and the optimum As(III) removal effect was occurred at pH 6 with more than 97%. K2FeO4 showed a great effect on the distribution and transformation of aluminum hydrolyzed polymers and then coupled with a variety of aluminum species produced by the hydrolysis of aluminum coagulants for arsenic removal. During enhanced coagulation, arsenic removal by AlCl3 was main through the charge neutralization of in situ Al13 and the sweep flocculation of Al(OH)3, while PACl1 mainly depended on the charge neutralization of preformed Al13 and the bridging adsorption of Al13 aggregates, whereas PACl2 mainly relied on the sweep flocculation of Al(OH)3. This study provided a new insight into the distribution and transformation of aluminum species for the mechanism of As(III) removal by K2FeO4 coupled with different Al-based coagulants.

Highly efficient removal of arsenate and arsenite with potassium ferrate: role of in situ formed ferric nanoparticle.

It is well known the capacity of potassium ferrate (Fe(VI)) for the oxidation of pollutants or co-precipitation and adsorption of hazardous species. However, little information has been paid on the adsorption and co-precipitation contribution of the Fe(VI) resultant nanoparticles, the in situ hydrolytic ferric iron oxides. Here, the removal of arsenate (As(V)) and arsenite (As(III)) by Fe(VI) was investigated, which focused on the interaction mechanisms of Fe(VI) with arsenic, especially in the contribution of the co-precipitation and adsorption of its hydrolytic ferric iron oxides. pH and Fe(VI) played significant roles on arsenic removal; over 97.8% and 98.1% of As(V) and As(III) removal were observed when Fe(VI):As(V) and Fe(VI):As(III) were 24:1 and 16:1 at pH 4, respectively. The removal of As(V) and As(III) by in situ and ex situ formed hydrolytic ferric iron oxides was examined respectively. The results revealed that As(III) was oxidized by Fe(VI) to As(V), and then was removed though co-precipitation and adsorption by the hydrolytic ferric iron oxides with the contribution content was about 1:3. For As(V), it could be removed directly by the in situ formed particles from Fe(VI) through co-precipitation and adsorption with the contribution content was about 1:1.5. By comparison, As(III) and As(V) were mainly removed through adsorption by the 30-min hydrolytic ferric iron oxides during the ex situ process. The hydrolytic ferric iron oxides size was obviously different in the process of in situ and ex situ, possessing abundant and multiple morphological structures ferric oxides, which was conducive for the efficient removal of arsenic. This study would provide a new perspective for understanding the potential of Fe(VI) treatment on arsenic control.

[Ultraviolet-initiated synthesis and characterization of anionic polyacrylamide].

APAM was prepared under the action of composite initiator and UV irradiation, using acryl amide (AM), 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and acrylic acid (AA) as raw materials. The paper studied the effect of proportion between monomers, monomer ratio, initiator concentration and other factors on intrinsic viscosity of the polymer, and optimized preparation conditions. The chemical structure and thermal stability of APAM were characterized by UV, FTIR, SEM and DTA-TGA respectively. The results showed that the APAM with the intrinsic viscosity 1.6 x 10(3) mL x g(-1) can prepared when the proportion between monomers was 70 : 10 : 10, the monomer ratio was 40%, initiator concentration was 0.20%, pH was 9 and the illumination time was 60 min.

[Determination of cationic degree in PDA with near infrared reflectance spectroscopy].

Cationic degree has been investigated as an important factor in polyacrylamide materials. Diallyl dimethyl ammonium chloride and acrylamide (PDA) was grafted by free radical polymerisation of acrylamide monomer (AM) onto the cationic monomer dimethyl diallyl ammonium chloride (DMDAAC). In the present study, near infrared reflectance spectroscopy (NIRS) was used as a rapid and accurate method to determine the cationic degree in the PDA. In this experiment, the near infrared spectra of 37 PDA samples that were self-prepared in the laboratory from 900.00 to 1 700.00 were collected. The characteristic peaks and the entire spectrum segment as the input layer neurons in radical basis function (RBF) were investigated for establishing the mathematical conversion NIRS calibration mode. For reduction of the NIR spectrum noise, the wavelet analysis was used as pretreatment process. The measured value was determined by using precipitation titration and a comparison between the simulated value and measured value was made. It was found that the external validation determination coefficient was more than 0.9, and the simulation value is in good agreement with the measured value. The statistics analysis showed that there was no significant difference between simulated value and measured value. Therefore, the calibration model (RBF neural network) established in this paper exhibited a remarkable feasibility for predicting the cationic degree of PDA based on the near infrared spectroscopy.

Bio-flocculation of Microcystis aeruginosa by using fungal pellets of Aspergillus oryzae: Performance and mechanism.

Algal blooms caused by eutrophication are global phenomena that seriously threaten the sustainable use of freshwater resources. Traditional water treatment chemicals often typically lead to high levels of residue and cause damage to the morphology of algal cells. This study investigated an eco-friendly fungal bio-flocculant, Aspergillus oryzae, to remove the representative microalgae (Microcystis aeruginosa). Furthermore, it explored crucial flocculation parameters, adsorption kinetics, and thermodynamics of microalgae using A. oryzae. Accordingly, a flocculation efficiency of >95% was achieved when the fungus was cultured for six days, flocculant dosage was 11 g/L, rotation speed was 100 rpm, temperature was 25 °C, flocculation time was 5 h, and pH ranged between 4.0 and 9.0. KEGG analysis based on the genomic data, and chemical composition analysis revealed that proteins and polysaccharides were the major components of metabolites. Zeta potential analysis, scanning electron microscopy, three-dimensional fluorescence, X-ray spectroscopy, and infrared spectroscopy, electrostatic attraction revealed that electrostatic attraction promoted the destabilization and aggregation of microalgae. Additionally, hyphal surface adsorption and chemisorption from extracellular proteins and exopolysaccharides aided in the removal of microalgae. Therefore, fungi-based bio-flocculants have the potential to remove microalgae in a simple, effective, and eco-friendly manner without the complex extraction of extracellular metabolites.

Chitin-biocalcium as a novel superior composite for ciprofloxacin removal: Synergism of adsorption and flocculation.

The ubiquitous present antibiotics in aquatic environment is attracting increasing concern due to the dual problems of bioaccumulation toxicity and antibiotic resistance. In this study, a low-cost chitin-biocalcium (CC) composite was developed by a facile alkali activation process from shell waste for typical antibiotics ciprofloxacin (CIP) removal. Response surface methodology (RSM) was utilized to optimize synthesis methodology. The optimized CC products featured superior CIP removal capacity of 2432 mg/g at 25 °C (adsorption combined with flocculation), rapid adsorption kinetics, high removal efficiency (95.58%) and wide pH adaptability (under pH range 4.0-10.0). The functional groups in chitin and high content of biocalcium (Ca2+) endowed CC abundant active sites. The kinetic experimental data was fitted well by pseudo-second-order and intraparticle diffusion model at different concentrations, revealing the removal was controlled by chemisorption and mass transport step. From the macroscopic aspect, flocs were produced with the increase of CIP concentration during the reaction, adsorption combined with flocculation were related to the CIP removal. From the microcosmic aspect, the superior removal performance was attributed to cation bridging, cation complexation among biocalcium-CIP and hydrogen bond between functional groups of chitin and CIP.

Agricultural waste-derived biochars from co-hydrothermal gasification of rice husk and chicken manure and their adsorption performance for dimethoate.

This study aimed to combine energy utilisation of agricultural wastes with the dimethoate (DT) adsorption from agricultural wastewater via hydrogen and biochar production using co-hydrothermal gasification (CHTG). The gasification behaviour after CHTG of five ratios of rice husk (RH) and chicken manure (CM) and the corresponding adsorption performance of biochars on DT were evaluated. The results demonstrated that the feedstock of 3RH+ 1CM achieved the maximum gas yield and hydrogen gasification efficiency (HGE), and the highest adsorption capacity of the derived biochars was 3.57 mg g-1. Surface characterisation and elemental analysis showed that the biochar derived under different C/N ratios varied considerably. The results of the isotherm and kinetic simulation showed that the Langmuir model and pseudo-first-order model best fitted the experimental data. The superior performance of agricultural waste-derived biochars (AWB) over five cycles of regeneration and adsorption indicated that AWB is a green and stable adsorption material for farmland tailwater. In addition, the degradation pathway of DT during hydrothermal gasification (HTG) regeneration of the spent adsorbent was comprehensively discussed. The CHTG treatment enhanced the yield of gaseous products from RH and CM and produced AWBs with high adsorption capacities for DT. This provides a green and efficient technology for resource utilisation of agricultural waste and treatment of agricultural wastewater using pesticide residues.

Efficient removal of cadmium by salts modified-biochar: Performance assessment, theoretical calculation, and quantitative mechanism analysis.

Modified biochar is a feasible adsorbent to solve cadmium pollution in water. However, few studies could elucidate the mechanism of cadmium adsorption by biochar from a molecular perspective. Furthermore, traditional modification methods are costly and have the risk of secondary contamination. Hence, several environmentally friendly sodium salts were used to modify the water chestnut shell-based biochar and employ it in the Cd2+ adsorption in this work. The modification of sodium salt could effectively improve the specific surface area and aromaticity of biochar. Na3PO4 modified biochar exhibited the highest Cd2+ adsorption capacity (112.78 mg/g). The adsorption of Cd2+ onto biochar was an endothermic, monolayer, chemisorption process accompanied by intraparticle diffusion. Microscopically, the enhancement of aromatization after modification made Cd2+ more likely to interact with the regions rich in π electrons and lone pair electrons. This study provided a new research perspective and application guidance for heavy metal adsorption on biochar.

[Preparation and structural analysis of diatomite-supported SPFS flocculant].

In the presetn study, polymerized ferric sulphate (PFS) flocculant was prepared and tested. In the preparation of PFS flocculant, industrial by-product ferrous sulfate heptahydrate (FeSO4.7H2O) was reused as the main material. By composition with diatomite and drying up at certain temperature in vacuum drying oven, solid PFS flocculant was produced. Structural characteristics of the new flocculant product were examined through infrared spectroscopy and scanning electron microscopy (SEM), which showed that by compositing with diatomite, new group bridging emerged in the structure of PFS, which made the bond of groups stronger. In addition, part of the metalic contents in diatomite was polymerized with PFS, the product of which was polymerized ferric complex. Furthermore, the absorbing and agglomerating capacity of the diatomite carrier was significant. Considering the factors listed above, the new solid polymerized ferric sulphate (SPFS) flocculant was characterized with a larger molecule structure and enhanced absorbing, bridging and rolling sweep capacities. Through orthogonal experiment, optimum conditions of synthesis were as follows: the ratio of FeSO4.7H2O/diatomite in weight was 43/1, the reaction time is 1 h and the reaction temperature is 55 degrees C. By wastewater treatment experiment, it was found that the synthetic products showed good flocculation performance in the treatment of domestic sewage, the removal of COD was 80.00% and the removal of turbidity was 99.98%.