Preparation, characterization of wheat residue based anion exchangers and its utilization for the phosphate removal from aqueous solution

Enhanced degradation of phenol by a novel biomaterial through the immobilization of bacteria on cationic straw

As phenol possesses a threat to human health, there is a great demand to search for fast and efficient methods for it to be discharged. In this study, a novel biomaterial was prepared by the immobilization of bacteria on a cationic straw carrier, and the remediation ability of the biomaterial on phenol-containing wastewater was investigated. The free bacteria could degrade 1,000 mg/L phenol within 240 h, while the prepared biomaterial was 192 h, shortening by 48 h that of free bacteria. In addition, the degradation tolerance of biomaterial increased from 1,000 mg/L to 1,200 mg/L than the free bacteria, within 216 h, which shortened by 24 h the degradation time of 1,000 mg/L phenol by free bacteria (240 h). Further, under different pH conditions, the degradation efficiency of phenol by prepared biomaterial was much higher than that of free bacteria. Especially for the lower pH 5, the degradation efficiency of biomaterial was nearly twice that of the free bacteria. This investigation demonstrates that this biomaterial has great potential in the field of remediation of organic pollution.

Recycling rice husk for removal of phosphate and nitrate from synthetic and swine wastewater: Adsorption study and nutrient analysis of modified rice husk

The objective of this study was to determine the adsorbent potential of rice husk and its modified form for phosphate and nitrate removal from synthetic and swine-farm wastewater. The mechanism of adsorption as well as the potential of phosphate-/nitrate- adsorbed rice husk as nutrient rich residue was also investigated. Two-step modification of RH (using base-washing (BW) and chemical modification (CM) was conducted to compare the phosphate and nitrate removal. The effects of several factors (pH, sorbent dosage, contact time, initial concentration, and coexistence of both ions) were investigated to gain insight into the adsorption rate, behavior, and mechanism of the modified RH regarding phosphate and nitrate removal. The results of Fourier-transform infrared spectroscopy showed that the modification was successful by crosslinking with the amine group of the chemical agent. Fitting the adsorption kinetic data of phosphate showed physical adsorption, intraparticle diffusion, and chemisorption, whereas for nitrate, the data indicated mainly chemisorption. Fitting the adsorption isotherm data of phosphate and nitrate together showed adsorption on a monolayer coating of anions on the homogeneous sorbent's surface. The maximum phosphate and nitrate adsorption capacities were 6.94 and 2.46 mg/g, respectively, for a single adsorbate and 11.14 and 1.76 mg/g, respectively, for the binary solution. In real swine wastewater, removal efficiencies of phosphate, nitrite, nitrate, sulfate, and ammonia were 83.8%, 65.0%, >45.0%, 36.6%, and 2.6%, respectively, indicating that the modified RH would be effective for phosphate and nitrate removal from real wastewater. Finally, nutrient analysis of the phosphate- and nitrate-sorbed RH showed increases in nitrogen and phosphorus, which would be beneficial for further use of the RH as nutrient or fertilizer after adsorption.

Phosphorus removal from aqueous solution using modified walnut and almond wooden shell and recycling as soil amendment

Modified walnut wooden shell (MWWS) and almond wooden shell (MAWS) as novel anion exchangers were used to remove phosphorus (P) from aqueous solution. The raw and modified agricultural wastes were characterized using total N, total P, FT-IR spectra, SEM, BET, and EXD analysis. The effect of different parameters such as pH (4 to 8), contact time (5 to 600 min), and adsorbent dosage (1 to 8 g L^-1) on P adsorption was investigated. Adsorption of P onto MWWS and MAWS was studied using the batch technique with different concentration of P (5 to 200 mg L^-1) at 25 ± 2 °C. The P adsorption isotherms were fitted with the Freundlich and Langmuir equations. The k and n values were 1.57 mg g^-1 and 1.88 for MWWS and 1.91 mg g^-1 and 2.24 for MAWS, respectively. The maximum P adsorption capacities for MWWS and MAWS were 22.73 and 14.71 mg g^-1, respectively. The desorption-regeneration experimental results indicated about 4% and 3% reductions in MWWS and MAWS P adsorption efficiency after four consecutive regeneration cycles, respectively. The data well fitted with Pseudo-second-order kinetic model (R² ≥ 0.99), indicating that chemical interactions dominate the P adsorption process. Incubation studies showed the rate of P release in treated soil with P-loaded modified biosorbents was higher than control. Therefore, the MWWS and MAWS can potentially be used as an excellent adsorbent in remediation of contaminated waters by P and then recycled to soil.

Chemical modifications of polysaccharides and their anti-tumor activities

With the rising trend of incidence of cancers, effective therapies are urgently needed to control human malignancies. However, the chemotherapy drugs currently on the market cause serious side effects. Polysaccharides belong to a class of biomacromolecules, which have drawn considerable research interest over the years as it possess anti-cancer activities or can increase the efficacy of conventional chemotherapy drugs with fewer side effects. The antitumor activity of many polysaccharides was significantly increased after modification. Based on these encouraging observations, a great deal of effort has been focused on discovering anti-cancer polysaccharides and modified derivatives for the development of effective therapeutics for various human cancers. This review highlights recent advances on the major chemical modification methods of polysaccharides, and discusses the effect of molecular modification on the physicochemical properties and anti-tumor activities of polysaccharides. Meanwhile, the underlying anti-tumor mechanisms of polysaccharide and its modified derivatives were also discussed.

Kinetics, thermodynamics and mechanisms of phosphate sorption onto bottle gourd biomass modified by (3-chloro-2-hydroxypropyl) trimethylammonium chloride

The sorption kinetics and thermodynamic parameters of phosphate removal from aqueous solution using quaternary ammonium–modified bottle gourd biomass as a sorbent were studied in a batch reactor. The cationic sorbent, containing trimethylammonium and hydroxypropyl groups, was obtained through the chemical reactions of the lignocellulosic Lagenaria vulgaris shell with (3-chloro-2-hydroxypropyl)trimethylammonium chloride. Experimental data of phosphate sorption from aqueous solutions of different initial concentrations (5–140 mg P L−1) have been analysed by reaction kinetics and diffusion models. The characteristic rate constants calculated by linear and non-linear regression analyses of the experimental results are presented. The phosphate sorption reaches equilibrium in 20–30 min, depending on the initial phosphate concentration. The maximum sorption capacity of quaternary ammonium–modified bottle gourd (QABG) sorbent was 18 mg P g−1 at 20 oC. The sorption system is best described by a non-linear equation of the pseudo first-order model ( R2 > 0.996). The Weber–Morris model indicated that the sorption process took place in three steps, whereby the intra-particle diffusion is not the only rate-controlling step. In addition, the effect of temperature (20 oC–50 oC) on sorption kinetics was also investigated. The various thermodynamic parameters suggest that phosphate sorption is favoured and is an exothermic process. The activation energy and the sticking probability confirmed that anion exchange is the dominant mechanism. These results provide valuable information for the potential use of agricultural residues in the treatment of wastewaters.

Effect of coexisting ions on Cr(VI) adsorption onto surfactant modified Auricularia auricula spent substrate in aqueous solution

In this paper, the effect of coexisting cations and anions on Cr(VI)(in the form of Cr₂O₇^2-) adsorption onto Auricularia auricula spent substrate (AASS) modified by cetyl trimethyl ammonium bromide (CTAB) was investigated in batch adsorption experiment. The Cr(VI) adsorption capacity of 9.327 mg/g, obtained at pH 3.0, 303 K, adsorbent dosage of 2 g/L, initial Cr(VI) concentration of 20 mg/L, rotational speed of 150 r/min for 120 min, was decreased in the presence of coexisting cations and anions, among which Pb²⁺ and PO₄^3- affected most by 21.79% and 12.43%, respectively. XRD, XPS and FTIR detection found that coexisting Pb²⁺ and PO₄^3- would not only interfere Cr(VI) to form crystals and reduce to Cr(III), but also compete with Cr(VI) for oxygen-containing and amino groups to form Pb-O and P-NH₂, respectively. In addition, the single Cr(VI) adsorption fitted with Langmuir isotherm model, while the competitive adsorption was well described by Freundlich isotherm model. Both single adsorption and competitive adsorption were in line with the pseudo-second-order kinetic model.

Fast microwave-assisted preparation of a low-cost and recyclable carboxyl modified lignocellulose-biomass jute fiber for enhanced heavy metal removal from water

A low-cost and recyclable biosorbent derived from jute fiber was developed for high efficient adsorption of Pb(II), Cd(II) and Cu(II) from water. The jute fiber was rapidly pretreated and grafted with metal binding groups (COOH) under microwave heating (MH). The adsorption behavior of carboxyl-modified jute fiber under MH treatment (CMJFMH) toward heavy metal ions followed Langmuir isotherm model (R(2)>0.99) with remarkably high adsorption capacity (157.21, 88.98 and 43.98mg/g for Pb(II), Cd(II) and Cu(II), respectively). Also, CMJFMH showed fast removal ability for heavy metals in a highly significant correlation with pseudo second-order kinetics model. Besides, CMJFMH can be easily regenerated with EDTA-2Na solution and reused up to at least four times with equivalent high adsorption capacity. Overall, cheap and abundant production, rapid and facile preparation, fast and efficient adsorption of heavy metals and high regeneration ability can make the CMJFMH a preferred biosorbent for heavy metal removal from water.

Preparation of cationized pine sawdust for nitrate removal: Optimization of reaction conditions

Anion exchange materials were prepared from pine sawdust (Pinus sylvestris, PSD) through cationizing treatment with N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride (CHMAC) in the presence of NaOH. Response surface methodology (RSM) was used to find the optimal reaction conditions. Three factors were chosen: reaction temperature (26-94 °C), reaction time (0.32-3.7 h) and NaOH/CHMAC molar ratio (0.19-2.2). Product yield (%) was used as a response. A quadratic model was fitted to the experimental data. The optimal conditions were: a reaction temperature of 57 °C, a reaction time of 1.8 h and a NaOH/CHMAC molar ratio of 1.32. A maximum nitrogen content of 2.6% was obtained at 60 °C, 3.7 h and a molar ratio of 1.2. The molar ratio had the greatest impact on the response. Regression analysis revealed that over 95% of the variance can be explained by the model. A maximum nitrate sorption capacity of 15.3 ± 1.4 mg N/g was achieved. The effect of CHMAC dose was also studied (a NaOH/CHMAC molar ratio of 1.2): 0.064 mol/g PSD was found to be near the optimum. Nitrate-contaminated groundwater (27.5 mg/l NO3) was treated with CPSD. Doses of 3-6 g/l resulted in 59-71% nitrate reduction.

Removal of As(iii) from water using modified jute fibres as a hybrid adsorbent

Jute fibres were modified to produce an effective hybrid adsorbent with the advantages of an excellent arsenic removal effect and easy retrieval from rivers or lakes.

Vanadium(V) removal from aqueous solution and real wastewater using quaternized pine sawdust

Cross-linked and quaternized pine sawdust was tested for vanadium removal from a synthetic aqueous solution as well as from real industrial wastewater which had a considerable amount of vanadium and other ions such as sulphate, ammonium and nickel. The maximum vanadium sorption capacity of the modified pine sawdust was found to be 130 mg/g in synthetic solution and 103 mg/g in real wastewater. Modified pine sawdust worked well over a wide range of pH. Column studies with real wastewater proved that vanadium was efficiently desorbed from the material with 2 M NaOH and that the material could be reused.

Modification of agricultural waste/by-products for enhanced phosphate removal and recovery: potential and obstacles

There is a growing trend to employ agricultural waste/by-products (AWBs) as the substrates for the development of phosphate biosorbents. Nevertheless, due to the lack of anion binding sites, natural AWBs are usually inefficient in phosphate decontamination. Consequently, modification plays a vital role in improving phosphate sorption's property of raw AWBs. This review paper evaluates all existing methods of modification. The literatures indicate that modification can significantly improve phosphate removal ability of AWBs by retaining phosphate ion onto modified AWBs principally via ion exchange (electrostatic interaction) and ligand exchange mechanisms. So far, little work has been done on the beneficial use of modified AWBs for the phosphorus recovery from aqueous solutions. The poor recyclability of modified AWBs could be responsible for their limited application. Hence, further study is essential to search for novel, cost-effective, and green methods of modification.

A potentially low-cost modified sawdust (MSD) effective for rapid Cr(vi) and As(v) removal from water

A potentially low-cost modified sawdust (MSD) was effective for the rapid removal of Cr(vi) and As(v) from water.

Characteristics of cellulosic amine-crosslinked copolymer and its sorption properties for Cr(VI) from aqueous solutions

A new cellulosic amine-crosslinked copolymer was prepared after the amination reaction with cotton stalk peel (CSP). The physicochemical characteristics of amine-crosslinked cotton stalk peel (AC-CSP) and raw CSP were determined after the surface analysis (including specific surface area, micropore volume and SEM), zeta potential analysis and spectrum analysis (FTIR and Raman spectrum). The sorption properties of AC-CSP for Cr(VI) were evaluated in the static, column sorption and desorption tests. The surface characteristics indicated the absence of porous adsorption in the potential Cr(VI) sorption mechanism. Zeta potential and spectrum analysis of AC-CSP illustrated the involvement of amine groups in the Cr(VI) sorption process. The sorption capacity of AC-CSP for Cr(VI) was 129.0mg/g as comparison with 14.8 mg/g of raw CSP. Flow rate and influent Cr(VI) concentration were demonstrated as two influencial factors in the column sorption tests. NaCl was used as the eluent, and the desorption efficiencies during three successive cycles were 75.9%, 69.8% and 64.3%, respectively. In addition, the results of the static, column sorption and desorption tests illustrated the complicated interactions between Cr(VI) and AC-CSP including complexation and ion exchange mechanisms.