RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION OF HEAVY METAL ADSORPTION IN A MULTIMETAL SOLUTION BY BENTONITE-KAOLIN-ZEOLITE PELLETS

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb > Cu > Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION OF HEAVY METAL ADSORPTION IN A MULTIMETAL SOLUTION BY BENTONITE-KAOLIN-ZEOLITE PELLETS

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb > Cu > Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

Bacterial Concrete: A Sustainable Building Material with Advantageous Properties

Bacterial concrete is concrete in which bacteria are embedded and is a material which exploits the metabolic functions of these specially selected bacteria, genus Bacillus. The bacteria are amalgamated within clay pellets along with the nutrient calcium lactate. When the concrete around the pellet cracks, the pellets break, and the bacteria metabolise the calcium lactate to produce insoluble calcium carbonate, filling cracks up to ~2 mm wide. The addition of the clay pellets and the bacteria to the concrete improves its compressive and tensile strengths, making it better suited for applications where the concrete must endure severe stress. Consequently, the modulus of toughness is improved, though the extent of the improvement depends on the grade of concrete used. Bacterial concrete is industrially advantageous as its low coefficient of permeability and high acid durability factor makes it less prone to corrosion and less likely to require extensive repairs. This is ideal for structures that are difficult or expensive to maintain as well as for use in motorways that endure corrosion from salt used in de-icing. This review will focus on the properties of bacterial concrete and its industrial use. It reveals that despite higher initial costs, the enhanced properties of bacterial concrete compared to conventional concrete, makes it a more sustainable material in the long run with an overall benefit to global carbon emissions.

Improvement of aqueous solution coexisting with arsenite and arsenate using iron mixed porous clay pellets in batch and fixed-bed column studies

Arsenic-polluted water is a global concern and puts millions of people at risk of developing cancer. The improvement of aqueous solution coexisting with arsenite and arsenate using iron mixed porous clay pellets was investigated in batch and fixed-bed column systems. Batch studies showed that the removal rate occurred in two main phases with an equilibrium time of 52 h. The pseudo-second-order model well described the experimental data. Isotherm data were well fitted by the Langmuir–Freundlich model. The removal efficiency was significantly reduced in alkaline solution and the presence of phosphate ions. The column study revealed that the breakthrough time and saturation time increased with lower feeding flow rate, higher bed height, and lower initial adsorbate concentration. The Thomas model provided good performance for predicting the column experimental data.

Rotary-screw systems for rotary kilns

The proposed paper examines rotary-screw systems for rotary kilns in the production of expanded clay. To reduce the size, reduce weight, increase productivity, simplify operation, reduce energy consumption in the production of expanded clay, the shell is made screw-shaped and mounted horizontally. Technical solutions protected by six patents of the Russian Federation are proposed, the structures of the shells of rotary kilns are shown, which, in comparison with the known structures of similar purpose, are made screw-shaped with internal spiral grooves. The dependence is proposed for determining the speed of movement of expanded clay pellets in a screw-shaped shell of a rotary kiln. A classification of rotary-screw systems for the production of expanded clay was developed.

Celtniecības keramika, keramzīts un keramiskie sorbenti

Vēsturiski viena no silikātu tehnoloģijas katedras pamattēmām vienmēr ir bijusi celtniecības materiālu pētīšana un jaunu materiālu izstrāde. Tie ir gan keramikas materiāli, gan materiāli uz neorganisko javu saistvielu bāzes. Ir analizētas un salīdzinātas šo materiālu īpašības: siltuma vadāmība, līdzsvara mitrums, mehāniskās īpašības. Salīdzinātas rūpnieciskos apstākļos un laboratorijā iegūtu dažādu Latvijas mālu keramikas materiālu īpašības un struktūra. Aprakstīta dažu rūpniecisko atkritumu ietekme uz keramikas materiālu īpašībām. Aprakstīta arī jauna keramikas materiāla keramzīta ražošanas tehnoloģija – vienas stadijas paņēmiens, kas ļauj paplašināt keramzīta ražošanai izmantojamo izejvielu bāzi un variēt keramzīta īpašības atkarībā no paredzamā pielietojuma. Pētīta dažādu Latvijas mālu noderība porainu keramisku sorbentu iegūšanai, par poru veidotājiem izmantojot organiskas dabas ražošanas atkritumus. Analizēta keramikas virsmas apstrāde, piemēram, apstarošana ar paātrinātajiem elektroniem un nanodaļiņu pārklājumi, keramikas granulu sorbcijas spējas palielināšanai un noderība fotokatalītiskai organisku piesārņotāju sadalīšanai.Building Ceramics, Expanded Clay, and Ceramic SorbentsInvestigation and development of new building materials historically was one of base research fields in the Institute of Silicate Materials. These are ceramic materials and materials based on inorganic binders. These materials have both advantages and disadvantages. Properties of these materials, such as thermal conductivity, equilibrium humidity and mechanical properties, are analysed and compared. Properties and structure of ceramic materials produced from Latvian clays in the laboratory and industrially were compared. Influence of addition of some industrial waste on the properties of ceramic materials was described. A new technology for obtaining expanded clay pellets was developed. It is a one-step technology that makes it possible to extend the basis of raw materials for production of expanded clay pellets and to produce pellets with different properties depending on the possible practical use. Usefulness of different Latvian clay for the production of porous ceramic sorbents was investigated. Organic industrial waste was added to function as pore former. A treatment of ceramic surface by irradiation with accelerated electrons or coating with nanoparticles was analysed. An increase of sorption activity of ceramic pellets or usefulness for the photocatalytic decomposition of organic pollution was the goal of the aforementioned treatment.Keywords – ceramics, expanded clay, equilibrium moisture, thermal insulation, ceramic granules, sorbents.

Enhancing the quality of arsenic-contaminated groundwater using a bio-sand filter with iron-mixed clay pellets

Many people in Cambodia consume groundwater with arsenic concentrations above the WHO guideline. In this study, an iron-mixed porous pellet adsorbent was put into a lightweight bio-sand filter to treat arsenic. The filter was intermittently charged daily with 30 L influent water until the effluent arsenic concentration exceeded 10 μg/L. The results indicated that the Morrill Dispersion Index was less than 2.0, implying that the filter had preferential plug flow. Head loss accumulation led to flow rate reduction over a period of 30 days. Arsenic removal efficiency was between 97 and 99% for the influent concentration, being in the range 355 to 587 μg/L. No significant leaching of iron or organic carbon was observed. The high dissolved oxygen concentration is likely to have contributed to the aerobic conditions in the filter bed. The filter removed arsenic more efficiently than was achieved in some previous studies and might be suitable to provide household-scale, arsenic-safe drinking water.

Synthesis of Expanded Clay Aggregate Pellets by Using Local Raw Materials

This study assesses the possible use of local raw materials (clays) for producing expanded clay pellets and test the product with American standard for test materials (ASTM) and according to ASTM C 330.For using them as lightweight aggregate in different construction applications, like thermal insulation, lightweight structural concrete , decoration pieces ,etc. The clay was collected from Al-Anbar province. The clay was bloated at 1150 C° without adding any impurities ,just mechanical treatment and perfect firing program, in order to obtain good bloating coefficient that is related with firing parameters (access time, temperature, socking time). We got the results of the match determined by the American specification (ASTM C330) and in which is considered lightweight aggregate. We got density about (280 kg / m3) which is much less than that determined by ASTM where the aggregate lightly if the density is less than (880 kg / m3).