Removing ammonium from contaminated water using Purolite C100E: batch, column, and household filter studies.

Ammonium removal from drinking water to protect human and environmental health is one of the major global concerns. This study evaluates the performance of Purolite C100E, a commercial cation exchange resin, in eliminating ammonium in synthetic and real contaminated groundwater. The results demonstrate that the pH operation range of the resin for better ammonium removal is 3 to 8. Lower ammonium removal at low and high pH occurred due to competition from H+ and loss of ammonium as ammonia gas, respectively. Equilibrium data of ammonium removal fitted both the Langmuir and Freundlich isotherm models with the maximum Langmuir ion exchange capacities for initial ammonium concentrations of 10-200 mg/L and 50-2000 mg/L, reaching 18.37 mg/g and 40.16 mg/g, respectively. The presence of co-ions in the water reduced the ammonium removal efficiencies slightly (< 12%) in the order Mg2+ > Ca2+ > K+. The higher affinity of ammonium to adsorbent is due to its lower hydrated ionic radius and H-bonding. The maximum exchange capacity in the fluidized bed studies of the original Purolite C100E (bed height 27 cm, resin weight 75 g, initial ammonium concentration 17.4 mg/L, filtration velocity 0.5 m/h) was 10.48 mg/g. It progressively reduced slightly after three regeneration cycles to 8.79 mg/g. The column breakthrough data satisfactorily fitted the Thomas model. A household filter cartridge packed with 4 kg Purolite C100E (80 cm height) and operated at a filtration velocity of 1.9 m/h in Vietnam successfully reduced the initial 6 mg NH4+/L in groundwater (after sand filter pre-treatment) to well below the Vietnam drinking water standard (3 mg/L-QCVN 01:2009/BYT) continuously for 1 week, suggesting that such a filter can be adopted in rural areas to successfully remove ammonium from groundwater.

Laterite as a low-cost adsorbent in a sustainable decentralized filtration system to remove arsenic from groundwater in Vietnam.

In the Red River Delta, Vietnam, arsenic (As) contamination of groundwater is a serious problem where more than seventeen million people are affected. Millions of people in this area are unable to access clean water from the existing centralized water treatment systems. They also cannot afford to buy expensive household water filters. Similar dangerous situations exist in many other countries and for this reason there is an urgent need to develop a cost-effective decentralized filtration system using new low-cost adsorbents for removing arsenic. In this study, seven locally available low-cost materials were tested for arsenic removal by conducting batch adsorption experiments. Of these materials, a natural laterite (48.7% Fe2O3 and 18.2% Al2O3) from Thach That (NLTT) was deemed the most suitable adsorbent based on arsenic removal performance, local availability, stability/low risk and cost (US$ 0.10/kg). Results demonstrated that the adsorption process was less dependent on the solution pH from 2.0 to 10. The coexisting anions competed with As(III) and As(V) in the order, phosphate > silicate > bicarbonate > sulphate > chloride. The adsorption process reached a fast equilibrium at approximately 120-360 min, depending on the initial arsenic concentrations. The Langmuir maximum adsorption capacities of NLTT at 30 °C were 512 µg/g for As(III) and 580 µg/g for As(V), respectively. Thermodynamic study conducted at 10 °C, 30 °C, and 50 °C suggested that the adsorption process of As(III) and As(V) was spontaneous and endothermic in nature. A water filtration system packed with NLTT was tested in a childcare centre in the most disadvantaged community in Ha Nam province, Vietnam, to determine arsenic removal performance in an operation lasting six months. Findings showed that the system reduced total arsenic concentration in groundwater from 122 to 237 µg/L to below the Vietnam drinking water standard of 10 µg/L.

In vitro antioxidant and anti-inflammatory activities of isolated compounds of ethanol extract from Sanchezia speciosa Leonard's leaves.

BACKGROUND: Sanchezia speciosa has been used in traditional medicine for gastritis treatment in Vietnam. Some phytochemical study showed that S. speciosa contains high amounts of flavonoids and cardiac glycoside compounds. In the present study, we isolated four compounds from the ethanol extract of the S. speciosa leaf, and we evaluated the in vitro antioxidant and anti-inflammatory effect of the isolated compound from the ethanol extract of the S. speciosa leaf. METHODS: The leaf of S. speciosa Leonard was extracted with ethanol 96%. Compounds were isolated using column chromatography and identified by spectroscopic method, including IR, MS, and NMR and by comparing their physicochemical and spectral data with those published in literatures. These isolated compounds were investigated for their antioxidant activity using DPPH and inflammation inhibitory activity by inhibition of albumin denaturation assay. RESULTS: We have isolated four compounds quercetin 3-O-α-l-rhamnopyranosid (quercitrin) (1), quercetin 3-O-ß-d-galactopyranosid (hyperosid) (2), sitosterol-3-O-ß-D-glucopyranosid (daucosterol) (3), and 3-methyl-1H-benz[f]indole-4,9-dione (4) from the ethanolic extract of the S. speciosa leaf. The antioxidant activities were in the following order: compound 2>compound 1>compound 4>compound 3. The IC50 values of scavenging DPPH radicals for compound 2 was 20.83±1.29 µg/mL. For anti-inflammatory activities, the order was compound 4>compound 3>compound 2>compound 1. Compound 4 showed the strongest inhibition, with IC50 values of 193.70±5.24 µg/mL. CONCLUSIONS: These compounds 1, 2, and 4 were isolated for the first time from the leaves of S. speciosa. These compounds showed strong antioxidant and anti-inflammatory activity.