Effect of Al in Slag Blended Cement Paste under Sulfate Attack

Unilateral sulfate attack of cementitious materials containing 40% slag with different water to binder ratios was investigated. The results showed that the degradation of slag blended cement pastes was nearly from the corners of paste surface with cracking and spallings, water-to-binder（w/b） ratio made a significant sense to the damage that low w/b ratio led to little weight loss, less cracking and spalling damage and vice versa. Microstructural experimental results demonstrated that in the three different stages of sulfate attack, degradation of pastes was primarily associated with the migration behavior and bonding configuration of aluminum, in the early ages Al was mostly present in C-（A）-S-H, and thus, the damage of pastes hardly appeared while at later ones Al had been largely transferred from C-（A）-S-H into AFt, leading to expansive damage.

Characterization of Sludge Produced by Treatment of Water from the Ribaa and Bittit Karstic Springs (Meknes, Morocco)

Problem Statement: Surface Water Treatment for potable supplies typically involves coagulation, flocculation, and processes. All water treatment plants produce sludge, during the purification of raw water, according to the level of the water turbidity. The aluminum sulfate is the most common coagulant used in water treatment plants of Morocco, as well as in many countries all over the world. It is difficult to manage sludge produced by the treatment plant. However, several studies, based on a set of jar test experiments, have demonstrated that it can be used in the process to improve the quality of the treated water and reduce the aluminum sulfate dose. Approach: In this study, the raw water treated and sludge produced in water treatment plant of Meknes, Morocco are investigated for chemical and bacteriological proprieties. The texture characterization of the dried sludge produced through the process of coagulation/flocculation and that of aluminum sulfate, used as coagulant aid, are obtained by nitrogen adsorption isotherms. Results: The physical properties of the raw water indicate its high turbidity during periods of heavy rainfall in the Bittit and Ribaa springs catchment area. However, these chemical properties indicate the quality of fresh water rich in magnesium, related to the dolomitic nature of the liastic aquifer. The bacteriological analysis of sludge produced in the treatment plant, confirms the elimination of pathogenic germs by the treatment process used. As regards the texture characterization the results demonstrated that the sludge presents some similarities with the sulfate. However, a clear difference is observed between the two solids, according to the pores distribution. Conclusions/Recommendations: Taking aluminum sulfate and sludge in comparison, it is possible to use the sludge for improving the coagulation process in water treatment.

Toxicity detection of sodium nitrite,borax and aluminum potassium sulfate using electrochemical method

Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an anaiyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose- glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions （solution pH 7.0, 37℃ and reaction for 3 hr）. The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be： sodium nitrite 〉 borax 〉 aluminum potassium sulfate 〉 blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.

Advanced lignin-acrylamide water treatment agent by pulp and paper industrial sludge: Synthesis, properties and application

A novel flocculant LA （lignin-acrylamide polymer）, which was used as aid for aluminum sulfate and polyaluminum chloride in this study, was prepared by grafting acrylamide onto lignin that deriving from pulp and papermaking sludge. Physicochemical properties of LA were measured by X-ray photoelectron spectroscopy and scanning electron microscopy. The experimental outcome indicated acrylamide was grafted onto the lignin backbone successfully. The effects of LA addition were evaluated on coagulation performance and floc characteristics as a function of aluminum （Al） dosage, such as floc size, growth rate, strength and recoverability. Effects of different dosing sequences, Al dosed first and LA dosed first, were also investigated. LA used as coagulant aid markedly enhanced the removal efficiency of turbidity and dissolved organic carbon, especially at low Al dosages. The dissolved organic carbon removal efficiencies of aluminum sulfate and polyaluminum chloride at the Al dosage range selected in this study were improved more than 30% and 5% by LA, respectively. LA dramatically enlarged floc size and it was in the order： Al dosed first 〉 LA dosed first 〉 Al. Floc strength and recoverability were also improved by LA. LA played a significant role in charge neutralization, adsorption and bridging in floc formation.

Fluoride removal by Al,Ti,and Fe hydroxides and coexisting ion effect

Batch experiments were conducted to evaluate fluoride removal by Al,Fe,and Ti-based coagulants and adsorbents,as well as the effects of coexisting ions and formation of aluminum–fluoride complexes on fluoride removal by co-precipitation with alum（Al_2（SO_4）_3·18H_2O）.Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8.Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3–5.Coexisting anions in water decreased the removal of fluoride in the order：phosphate（2.5 mg/L） 〉 arsenate（0.1 mg/L） 〉 bicarbonate（200 mg/L） 〉sulfate（100 mg/L） = nitrate（100 mg/L） 〉 silicate（10 mg/L） at a pH of 6.0.The effect of silicate became more significant at pH 〉 7.0.Calcium and magnesium improved the removal of fluoride.Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al（OH）_3 precipitates from 8.9 to 8.4,indicating the chemical adsorption of fluoride at the surface.The presence of fluoride in solution significantly increased the soluble aluminum concentration at pH 〈 6.5.A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF^（2＋）,AlF^（＋2）,and AlF_3complexes.The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate.

Synthesis of Micro-Mesoporous Ti-MOR/Silica Composite Spheres in Oil-in-Water Microemulsion System

The hierarchically structured micro-mesoporous spheres(MMS) composed of mesoporous silica and Ti-containing mordenite (Ti-MOR) zeolite were self-assembled in an oil-in-water microemulsion system containing tetrabutyl orthosilicate as silica source, cetyltrimethylammonium bromide as template and aluminum sulfate as additive. The composite materials possessed the connatural microporosity of zeolite together with the disordered mesopores(5.41 nm) in silica part. With a special focus on the importance of aluminum sulfate additive, a possible formation mechanism has been proposed, in which double electrostatic interactions played the crucial role of mediating the mesosilica species and zeolite crystals. The obtained MMS materials, with a tunable particle dimension(250-720 μm) and a changeable content of active component Ti-MOR(44%-70%), showed enhanced catalytic activity and lifetime in the liquid-phase ammoximation of cyclohexanone in comparison to the parent Ti-MOR powder.

Effects of different soil amendments on physicochemical property of soda saline-alkali soil and crop yield in Northeast China

Soil amendment is one of the most effective methods to improve saline-alkali soil.In this study,laboratory experiments were conducted to verify the effect of 13 kinds of amendments and their combinations(Citric acid(NM),Phosphogypsum(LS),Aluminum sulfate+citric acid(AL+NM),Aluminum sulfate+phosphogypsum(AL+LS),Aluminum sulfate+citric acid+phosphogypsum(HH),Zeolite(Z),Acidified zeolite(ZH),Aluminum sulfate(AL),Aluminum sulfate+zeolite(AL+Z),Aluminum sulfate+acidified zeolite(AL+ZH),Poly Aluminum chloride(ALCL),Polyaluminium chloride+zeolite(ALCL+Z),Polyaluminium chloride+acidified zeolite(ALCL+ZH))on soil pH,metal cations content,exchangeable Na+,exchangeable sodium percentage(ESP)in the lab.And then the five most effective amendments(Z,ZH,AL,AL+Z,and AL+ZH)were chosen applying both in dry field(maize field)and paddy field to evaluate their improvement on soda saline-alkali soil and crop yield in the northeast Songnen Plain,China.The lab results showed that AL,AL+Z and AL+ZH treatments could significantly reduce the pH in soil solution and increase the content of metal cations.Z and ZH treatments could adsorb metal cations in soil.Both in dry and paddy fields,all five treatments could increase the soil saturated hydraulic conductivity(Ks),increased from 9.63 to 60.02 mm/d and 0.18 to 33.25 mm/d,respectively,of which the AL treatment was the best;all five treatments could reduce the content of exchangeable Na+in soil,and decrease by 38.62%-61.33%and 25.24%-71.53%,respectively,of which the AL+ZH treatment was the best;all treatments could reduce soil exchangeable sodium percentage,and decrease by 0.14-0.22 and 0.14-0.41,respectively,of which the AL+ZH treatment was the best;AL,AL+Z and AL+ZH treatments could improve soil organic matter content;all treatments could effectively improve the yield of crops,and increase 23.98%-60.75%and 52.51%-260.21%,respectively,of which the AL treatment was the best in dry field and the AL+ZH treatment was the best in paddy field.The effect of AL treatment was the best in dry field and AL+ZH treatment was the best in paddy field of soda saline-alkali soil.This study could provide instructive information for the chemical improvement and agricultural utilization of soda saline-alkali soils in the world.