Chuanyi Peng

Adsorptive removal of fluoride from drinking water using porous starch loaded with common metal ions

In this study, porous corn starch was loaded with Zr, Al, Fe or La to produce the composites PS-Zr, PS-Al, PS-Fe and PS-La. Fluoride adsorption from water was tested at different biosorbent dosages, contact times, solution pH values and initial fluoride concentrations. The biosorbents were characterized by microscopy and spectroscopy. PS-Zr was shown superior defluoridation capacity over a pH range of 3.0-9.0. The adsorption process could be described by the Langmuir isotherm model and the Lagergren pseudo-second-order kinetic model. The maximum fluoride adsorption capacity calculated to be for PS-Zr was 25.41mg/g. Our results revealed that PS-Zr could be employed as an effective biosorbent for removal of fluoride from drinking water.

Enhanced removal of fluoride by tea waste supported hydrous aluminium oxide nanoparticles: anionic polyacrylamide mediated aluminium assembly and adsorption mechanism

A novel and low-cost biosorbent of tea waste supported hydrous aluminium oxide (Tea–APAM–Al) was prepared with help of anionic polyacrylamide (APAM) for highly efficient defluoridation of drinking water. Batch adsorption studies were carried out by varying the adsorbent dosage, initial fluoride concentration, contact time, initial pH, and presence of co-existing ions to evaluate the efficiency of fluoride removal. It was found that Tea–APAM–Al performed well over a considerably wide pH range, from 4.0–9.0. With the exception of bicarbonate, other co-existing ions (nitrate, chloride and sulphate) did not have a significant effect on the defluoridation process. The adsorption process could be described by the Lagergren pseudo-second-order kinetic model. Adsorption data could be fitted by the Langmuir isotherm model and the maximum fluoride adsorption capacity for Tea–APAM–Al was 42.14 mg g−1. The results from SEM, EDS, XRD, FTIR and XPS studies showed that the fluoride adsorption mechanism likely involved hydroxyl and sulfate ion exchange with fluoride. Moreover, fluoride anion exchange with sulfate ions was the main mechanism for fluoride adsorption at low initial fluoride concentration.

Enhanced fluoride removal by loading Al/Zr onto carboxymethyl starch sodium: synergistic interactions between Al and Zr

In this paper, a novel type of adsorbent was prepared by loading Al/Zr onto carboxymethyl starch sodium to generate CMS–Al, CMS–Zr or CMS–Al–Zr. The adsorbents were tested for removal of fluoride by batch adsorption experiments under various conditions. It was found that CMS–Al–Zr performed well over a considerably wide pH range of 4–10. The adsorption process could be described by a Langmuir isotherm model and Lagergren pseudo-second-order kinetic model. The maximum adsorption capacity for CMS–Al–Zr (60.61 mg g−1) was higher than CMS–Al (51.44 mg g−1) and CMS–Zr (40.23 mg g−1) due to synergistic interactions between Al and Zr. SEM, EDS, XRD, FTIR and XPS studies revealed the Al/Zr loading process and mechanism of fluoride adsorption. The results showed that the metal complex was coordinated to the –COO group of CMS through ion exchange of sodium during the loading process.

Critical factors determining fluoride concentration in tea leaves produced from Anhui province, China.

This study investigated the fluoride present in tea plants (Camellia sinensis (L.) O. Kuntze) and its relationship to soils, varieties, seasons and tea leaf maturity. The study also explored how different manufacturing processes affect the leaching of fluoride into tea beverages. The fluoride concentration in the tea leaves was significantly correlate to the concentration of water-soluble fluoride in the soil. Different tea varieties accumulated different levels of fluoride, with varieties, Anji baicha having the highest and Nongkang zao having the lowest fluoride concentration. In eight different varieties of tea plant harvested over three tea seasons, fluoride concentration were highest in the summer and lowest in the spring in china. The fluoride concentration in tea leaves was directly related to the maturity of the tea leaves at harvest. Importantly, the tea manufacturing process did not introduced fluoride contamination. The leaching of fluoride was 6.8% and 14.1% higher in black and white tea, respectively, than in fresh tea leaves. The manufacturing step most affecting the leaching of fluoride into tea beverage was withering used in white, black and oolong tea rather than rolling or fermentation. The exposure and associated health risks for fluoride concentration in infusions of 115 commercially available teas from Chinese tea markets was determined. The fluoride concentration ranged from 5.0 to 306.0mgkg(-1), with an average of 81.7mgkg(-1). The hazard quotient (HQ) of these teas indicated that there was no risk of fluorosis from drinking tea, based on statistical analysis by Monte Carlo simulation.

Aluminum and Heavy Metal Accumulation in Tea Leaves: An Interplay of Environmental and Plant Factors and an Assessment of Exposure Risks to Consumers: Accumulation and risk of metals in tea…

Environmental and plant factors (soil condition, variety, season, and maturity) and exposure risks of aluminum (Al), manganese (Mn), lead (Pb), cadmium (Cd), and copper (Cu) in tea leaves were investigated. The concentrations of these metals in tea leaves could not be predicted by their total concentrations in the soil. During any one season, there were differences in Al, Mn, and Cd levels between tea varieties. Seasonally, autumn tea and/or summer tea had far higher levels of Al, Mn, Pb, and Cd than did spring tea. Tea leaf maturity positively correlated with the concentrations of Al, Mn, Pb, and Cd, but negatively with Cu. The calculated average daily intake doses (mg/ [kg•d]) for these metal elements were 0.14 (Al), 0.11 (Mn), 2.70 × 10-3 (Cu), 2.80 × 10-4 (Pb), and 2.88 × 10-6 (Cd). The hazard quotient values of each metal were all significantly lower than risk level (=1), suggesting that, for the general population, consumption of tea does not result in the intake of excessive amounts of Al, Mn, Pb, Cd, or Cu. This study identified the factors that can be monitored in the field to decrease consumer exposure to Al and Mn through tea consumption. PRACTICAL APPLICATION Environmental and plant factors influence aluminum and heavy metal accumulation in tea leaves. Consumers of tea are not ingesting excessive Al, Mn, Pb, Cd, or Cu. Trackable factors were identified to manage exposure levels.

Highly selective defluoridation of brick tea infusion by tea waste supported aluminum oxides

BACKGROUND Brick tea usually contains very high fluoride, which may affect human health. Biosorbents have received much attention for selective removal of fluoride because of low cost, environmental friendliness, and relative safeness. RESULTS In the present study, a highly selective fluoride tea waste based biosorbent, namely, aluminum (Al) oxide decorated tea waste (Tea-Al), was successfully prepared. The Tea-Al biosorbent was characterized by energy-dispersive spectrometry, Fourier transform infrared spectroscopy, powder X-ray diffraction and X-ray photoelectron spectroscopic analysis. The Tea-Al sample exhibited remarkably selective adsorption for fluoride (52.90%), but a weaker adsorption for other major constituents of brick tea infusion, such as catechins, polyphenols and caffeine, under the same conditions. Fluoride adsorption by Tea-Al for different times obeyed the surface reaction and adsorption isotherms fit the Freundlich model. In addition, the fluoride adsorption mechanism appeared to be an ion exchange between hydroxyl and fluoride ions. CONCLUSION Results from this study demonstrated that Tea-Al is a promising biosorbent useful for the removal of fluoride in brick tea infusion.

Fumarate-based metal-organic frameworks as a new platform for highly selective removal of fluoride from brick tea

Adsorption and removal of fluoride from brick tea is very important but challenging. In this work, two fumarate-based metal-organic frameworks (MOFs) were synthesized for the selective removal of fluoride from brick tea infusion. MOFs were examined for adsorption time, effect of dose, and uptake capacity at different initial concentrations and temperatures. Remarkably, over 80% fluoride removal was achieved by MOF-801 within 5 min at room temperature, while no significant adsorption occurred for the catechins and caffeine in the brick tea infusion. Further, with the use of the Langmuir equation, the maximum fluoride uptake capacity for the nontoxic calcium fumarate (CaFu) MOF was calculated to be as high as 166.11 mg g−1 at 373 K. As observed from FTIR, EDX and XPS results, hydroxyl group in MOFs were substituted by fluoride. This work demonstrates that the novel fumarate-based MOFs are promising materials for the selective removal of fluoride from brick tea infusion.

Rinsing Tea before Brewing Decreases Pesticide Residues in Tea Infusion

Rinsing dried tea leaves before brewing is a traditional way of preparing rolled oolong tea in China. This study analyzes how rinsing green, black, and oolong tea before brewing affects the levels of pesticide residues in the tea infusion. Eight representative insecticides of different polarities were tracked, namely, three neonicotinoids (acetamiprid, imidacloprid, and thiamethoxam), two organophosphates (dimethoate and malathion), and three pyrethroids (bifenthrin, β-cypermethrin, and fenvalerate). The results showed that the eight pesticides transferred into the rinse water at rates between 0.2 and 24% after 5, 10, 20, or 30 s. Rinsing tea before brewing reduced the pesticide risk levels by 5-59% in the tea infusion. Five functional components, such as epigallocatechin gallate and caffeine, were reduced by 0-11% in the tea infusion. The results can be used to develop an effective method of rinsing tea before brewing that reduces pesticide exposure risks.

Migration kinetics of four photo-initiators from paper food packaging to solid food simulants

ABSTRACT The migration behaviour of four photo-initiators (BP, EHA, MBP and Irgacure 907) was studied by ‘printing’ onto four different food-packaging materials (Kraft paper, white cardboard, Polyethylene (PE)-coated paper and composite paper) and tracking movement into the food simulant: Tenax-TA (porous polymer 2,6-diphenyl furan resin). The results indicated that the migration of the photo-initiators was related to the molecular weight and log Ko/w of each photo-initiator. At different temperatures, the migration rates of the photo-initiators were different in papers with different thicknesses. The amount of each photo-initiator found in the food was closely related to the food matrix. The Weibull model was used to predict the migration load into the food simulants by calculating the parameters τ and β and determining the relationship of the two parameters with temperature and paper thickness. The established Weibull model was then used to predict the migration of each photo-initiator with respect to different foods. A two-parameter Weibull model fitted the actual situation, with some deviation from the actual migration amount.

Determination of 11 photoinitiators and their migration into tea and milk by gas chromatography-tandem mass spectrometry (MSPD-GC-MS/MS)

Based on the use of multi-walled carbon nanotubes (MWCNTs) in matrix solid-phase dispersion (MSPD) extraction, a novel, rapid and reliable method was developed for the analysis of 11 photoinitiators used in food packaging ink followed by quantitation by gas chromatography-tandem mass spectrometry. The use of MWCNTs was compared with that of the adsorbents C18 silica and diatomaceous earth (DE) in the MSPD procedure. The extracts obtained using MWCNTs were better than those obtained using C18 and DE. Using the newly developed method, recoveries ranged from 70.9% to 121.4%, the RSDs were between 0.1% and 3.5%, and the LOQs ranged from 0.002–0.008 mg kg−1. This method was used to test the degree of migration of the photoinitiators into food, showing that the migration into tea powder increased with increasing initial concentration of the pollutants, while this phenomenon was not found in milk powder. The ability of the photoinitiators to migrate into food matrices was shown to be closely related to their molecular weight and to their molecular conformation, as well as the particular characteristics of the food matrix.