Study of Semi-Dry High Target Solidification/Stabilization of Harmful Impurities in Phosphogypsum by Modification

Phosphogypsum (PG) treatment is one of the research hotspots in the field of environmental protection. Many researchers both at home and abroad have devoted themselves to studies on harmless resource treatment of PG, but the treatment technology is unable to meet the demand of PG consumption due to the huge production and storage demands. In order to solve the problem of PG pollution, this study explored the different solidified effects of various modification formulations on the hazardous components in PG, using industrial solid waste calcium carbide slag (CCS) as an alkaline regulator; Portland cement (PC), polyaluminum chloride (PAC) and CaCl2 as the main raw materials of the solidification and stabilization formula and the water content in PG as the reaction medium. The results showed that CCS (0.5%), PC (0.4%) and PAC (0.3%) had a more significant solidified effect on phosphorus (P) and fluoride (F). PAC was added in two steps and reacted under normal temperature and pressure, and its leaching toxicity meets the requirements of relevant standards, which laid an excellent foundation for PG-based ecological restoration materials and filling materials, with low economic cost, simple process and strong feasibility. This will provide great convenience for the later mining and metallurgy.

The new life of traditional water treatment flocculant polyaluminum chloride (PAC): a green and efficient micro–nano reactor catalyst in alcohol solvents

The polyaluminum chloride–ethanol micro–nano reactor is a green, efficient, easy-to-handle and economical catalyst for catalyzing organic synthesis reactions.

Effect of the Polymerized Titanium Ferric Sulfate (PTFS) Coagulant on Sedimentation of Coal Slime Water

High efficiency slime water settlement is very important for ensuring washing water recycling in coal preparation plants. In order to improve the sedimentation of coal slime water, an iron ion-based coagulant was prepared by titanium ion complexation action using titanium sulfate as a main raw material, Fe3+ and NaH2PO3 as a stabilizer and NaHCO3 as an alkalizing agent. The particle size distribution of coal slime was measured, and the sedimentation test for coal slime water was carried out with PAM, polyaluminum chloride and polymerized titanium ferric sulfate (PTFS), respectively. Then, coal slime water sedimentation was investigated at different PAM dosages and polyaluminum chloride or coal slime water of PTFS with various molar ratios of PAM and ferrotitanium. The results showed that PAM and polyaluminum chloride could not make coal slime settle down, and PTFS showed a poor settlement effect. When polyaluminum chloride and PTFS were used together with PAM, it produced a molecular weight of 3 million respectively. Polyaluminum chloride needs 6.66 × 10−10 mol of PAM, PTFS needs 0.66 × 10−10 mol of PAM and the effect of sedimentation is improved. When the molar ratio of PTFS was 1:7, polymerization performance was effective. The sedimentation effect of PTFS was better than that of polymeric aluminum chloride coagulant usually used in coal preparation plants, especially when combined with flocculant, and high efficiency was reached. The surface potential and surface free energy of coal slime particles before and after adding coagulant were measured and analyzed by XDLVO theory to explain the action mechanism of PTFS coagulant. Experimental results demonstrated that PTFS can significantly improve the sedimentation of coal slime water, save the dosage of PAM and increase economic benefit.

In-process tests of river water conditioning for domestic and drinking water supply in the city of Kurgan

Рассматривается опыт применения озонирования речной воды в лабораторных и пилотных масштабах. Вода реки Тобол – жесткая минерализованная со средними значениями цветности 24 град, содержанием марганца в зимний период более 0,8 мг/дм3. После определения рабочих доз реагентов (коагулянт гидроксохлорид алюминия, флокулянт Praestol 650TR) проводилось пробное озонирование с последующей реагентной обработкой на лабораторном флокуляторе. Для достижения норматива по содержанию марганца в речной воде 0,1 мг/дм3 потребовались высокие дозы озона – от 35 мг/дм3. Подщелачивание исходной воды до рН 9 позволило снизить дозу озона до 23 мг/дм3. Снижение цветности до 15 град происходит при дозах озона 6–7 мг/дм3. Очистка речной воды на пилотной установке производительностью 50 л/ч проводилась по полной технологической схеме (озонирование, обработка коагулянтом и флокулянтом, отстаивание, фильтрование через песчаный фильтр, фильтрование через угольный фильтр, опреснение-умягчение обратным осмосом). Доза коагулянта составляла 5 мг/дм3, флокулянта – 0,3 мг/дм3. В стационарном режиме работы пилотной установки при дозе озона 25 мг/дм3 были достигнуты следующие показатели качества фильтрата песчаного фильтра: цветность 5–7 град; марганец 0,05–0,15 мг/дм3; железо общее 0,02–0,03 мг/дм3; алюминий 0,05–0,08 мг/дм3; перманганатная окисляемость 3–4 мг/дм3. Исходя из расчетных показателей состава воды р. Тобол, для концентрации марганца в воде 0,8 мг/дм3теоретическая доза озона составляет ≈ 8 мг/дм3, проектная доза озона может быть принята 10 мг/дм3 (г/м3). The experience of using ozonation of river water on a laboratory and pilot scale is considered. The water of the Tobol River is hard and mineralized with an average color value of 24 degrees, a manganese concentration in the winter period of more than 0.8 mg/dm3. After determining the operational doses of the chemicals (polyaluminum chloride coagulant, Praestol 650TR flocculant), test ozonation was carried out followed by the chemical treatment in a laboratory flocculator. To achieve the standard for manganese concentration in river water of 0.1 mg/dm3, high doses of ozone were required – from 35 mg/dm3. Alkalinization of the initial water to pH 9 provided for reducing the ozone dose to 23 mg/dm3. A decrease in color to 15 degrees occurred at ozone doses of 6–7 mg/dm3. River water purification at a pilot plant with a capacity of 50 l/h was carried out according to the complete process flow scheme (ozonation, treatment with coagulant and flocculant, sedimentation, filtration in a sand filter, filtration in a carbon filter, desalination-softening by reverse osmosis). The coagulant dose was 5 mg/dm3, and that of the flocculant – 0.3 mg/dm3. In the steady run of the pilot plant at an ozone dose of 25 mg/dm3, the following quality indicators of the sand filter filtrate were achieved: color 5–7 degrees; manganese 0.05–0.15 mg/dm3; total iron 0.02–0.03 mg/dm3; aluminum 0.05–0.08 mg/dm3; permanganate index 3–4 mg/dm3. Based on the estimate indicators of the Tobol River water composition related to the manganese concentration in water of 0.8 mg/dm3, the theoretic dose of ozone is ≈ 8 mg/dm3, the design dose of ozone can be assumed as 10 mg/dm3 (g/m3).

Study of production 500 kg/batch polyaluminum chloride from aluminum hydrate

Polyaluminum chloride (PAC) is commonly used as a chemical in the water treatment industry, deodorant and paper-making. The PAC is a complex inorganic substance between hydroxyl and aluminum ions that gradually takes place chlorination with its general formula of Alx(OH)yCl3x-y. It has the ability to coagulate suspended solid or dispersed colloid within water perform easily precipitated flock. The raw materials used for manufacturing liquid PAC consists of hydrated alumina (Al(OH)3), hydrochloric acid (HCl), sulfuric acid (H2SO4) and calcium carbonate (CaCO3). A pilot-scale experiment with a capacity of 500 kg/batch feed was conducted by reacting Al(OH)3 with HCl and H2SO4, then neutralized using CaCO3 to obtain liquid PAC and gypsum as a by-product. The variation of acid concentration as reactant and reaction time were conducted to determine its effect on the composition of PAC and the amount of gypsum produced. The optimum experiment produced liquid PAC with the highest Al2O3 composition of 11.96% and the lowest Cl− ion of 10.87% at 2 hours reaction time with a total acid concentration of 37.74%.

Effects of polyaluminum chloride (PAX-18) on the relationship between predatory fungi and Lecane rotifers

PAX-18 (polyaluminum chloride) is frequently used in WWTPs (wastewater treatment plants) to overcome sludge bulking. An alternative biological method is the usage of Lecane rotifers, which can be endangered by predacious fungi. We investigated the influence of different PAX-18 concentrations on the relationship between Lecane inermis and predacious fungi (Zoophagus and Lecophagus) differing in feeding mode. High PAX concentration (6 mg Al3+ L−1) strongly limited the number of the rotifers, which in low concentration (1.2 mg Al3+ L−1), after an initial decline, increased, but significantly slower than in control. Under the simultaneous influence of Lecophagus and PAX, rotifers were driven almost extinct at the high concentration, but survived at the lower concentration and increased in the control. When treated with Zoophagus, only one or two rotifers survived in treatments and control. High concentrations of PAX significantly restricted the growth of fungi, whereas in low concentrations and control conditions, their length increased, with Zoophagus growing much quicker than Lecophagus. Zoophagus was significantly more efficient in trapping rotifers regardless of PAX concentration. The trapping ability of mycelium following extended exposure to PAX was strongly limited at high concentrations, in comparison to control. Conidia of Zoophagus turned out to be considerably more resistant to PAX-18 and starvation than Lecophagus conidia.

Chemically Enhanced Solid–Liquid Separation of Digestate: Suspended Solids Removal and Effects on Environmental Quality of Separated Fractions

Chemically enhanced solid–liquid separation (CES) of digestate can improve its membrane filterability but potentially influence the environmental features of the separated solid fraction, thus hindering its possible agricultural reuse. In this study, the effects were assessed of different dosages of polyaluminum chloride (PAC), epichlorohydrine-dimethylamine with ethylendiamine (DEED) and polyacrilamides (PAM) on CES of digestate from biowaste in terms of Total Suspended Solid (TSS) mitigation in the liquid fractions and resulting environmental quality of the solid fractions. Results from lab-scale trials showed that applied chemicals significantly increased the centrifugation efficiency with achieving minimum TSS concentration of 2347 ± 281 mgTSS/L (up to 90% improved TSS mitigation). Also, performed treatments led to almost complete removal of P and Heavy Metals (HMs) from the liquid fractions after centrifugation. Conditioned solid fractions showed higher Al (reaching 20 g kg−1 TS), organic carbon and nitrogen content (up to 324 mgTOC kg−1 TS and 44.1 mgTKN kg−1 TS, respectively) due to residual PAC, DEED and PAM. However, achieved concentrations of HMs guaranteed full consistency with EU regulation limits established for agricultural reuse of organic soil amendments. Further, leaching tests performed on the treated solid fractions indicate higher chlorides and soluble Al concentrations in the water extracts (up to 4.6 g L−1 and 2.3 g L−1, respectively), but lower HMs leachability from the digestates undergone CES. Nevertheless, water extracts from treated biosolids were characterized by higher phytotoxicity, likely related with direct Al toxicity and increased salinity due to chemicals addition. Accordingly, the effects on soil–plant system should be better investigated when agricultural reuse of CES-treated solid fraction of digestate is foreseen. Graphic abstract