Efficient Solar-Driven Water Purification Based on Biochar with Multi-Level Pore Bundle Structure for Preparation of Drinking Water

Water is an important source for humankind. However, the amount of available clean water has rapidly reduced worldwide. To combat this issue, the solar-energy-driven evaporation technique is newly proposed to produce clean water. Here, biochar derived from sorghum stalk with a multi-level pore bundle structure is utilized to fabricate a solar-driven evaporator for the first time. The biochar displays rapid water transfer and low thermal conductivity (ca. 0.0405 W m−1 K−1), which is vitally important for such an application purpose. The evaporation rate and energy conversion efficiency of the solar evaporator based on carbonized sorghum stalk can achieve up to 3.173 kg m−2 h−1 and 100%, respectively, which are better than most of the previously reported biomass materials. Furthermore, the carbonized sorghum stalk also displays good resistance to salt crystallization, anti-acidic/basic, and organic pollutants by producing drinking water using seawater, acidic/basic waste water, and organic polluted water, respectively. The direct application of processed water in food production was also investigated. The present solar steam evaporator based on the carbonized sorghum stalk has the potential to create practical drinking water production by using various water sources.

Key parameters of volcanic tuffs used as building stone: a statistical approach

Volcanic tuffs naturally show a strong heterogeneity in their petrography and petrophysical properties. The arrangement of the components in tuffs can create a very wide spectrum of porosities and fabrics, which in turn can lead to a highly differential weathering behavior. Considerable amounts of clay minerals and zeolites are common and can contribute to a high sensitivity to expansional processes and salt crystallization. Understanding the influence of the rock properties on material behavior and durability can help to make predictions on future material behavior and evaluate the suitability of the material for construction purposes. This study presents the petrographic and petrophysical data of 15 selected tuffs and 513 tuffs from the literature used as building stones. Regression analysis show if parameters are comparable and if key parameters can be identified. Key parameters can potentially be used for the estimation of the material behavior, without the use of expensive analytics or weathering simulations.

Co-Deposition Mechanisms of Calcium Sulfate and Calcium Carbonate Scale in Produced Water

Co-precipitation of mineral-based salts during scaling remains poorly understood and thermodynamically undefined within the water industry. This study focuses on investigating calcium carbonate and calcium sulfate mixed precipitation in scaling. Scaling is often observed in the produced water supply as a result of treatment processes. Co-precipitation results were compared with experimental results of a single salt crystallization. Several parameters were carefully monitored, including the electrical conductivity, pH value, crystal morphology and crystal form. The existence of the calcium carbonate scale in the mixed system encourages the loose calcium sulfate scale to become more tightly packed. The mixed scale was firmly adhered to the beaker, and the adhesion of the co-deposition product was located between the pure calcium sulfate scale and the pure calcium carbonate scale. The crystalline form of calcium sulfate was gypsum in both pure material deposition and mixed deposition, while the calcium carbonate scale was stable in calcite form in the pure material deposition. In the co-deposition, apart from calcite form, some calcium carbonate scale crystals had metastable vaterite form. This indicated that the presence of SO42− ions reduced the energy barrier of the calcium carbonate scale and hindered its transformation from a vaterite form to a calcite one, and the increase in HCO3− content inhibited the formation of calcium sulfate scale.

Effects of Water on Natural Stone in the Built Environment—A Review

The present work reviews studies with information on the effects of water by itself on stones of the built environment both to assess the impact of this substance and to discuss possible implications for conservation. The analysis concerns empirical results from previous publications dealing with the effects, on several rock types, of freeze–thaw, wetting, erosion by running water and substances resulting from the water–stone interaction. Laboratory studies have shown that water freezing can cause physical damage even in low porosity rocks. As far as we know, this is the first review that considers comparative laboratory studies of freeze–thaw and salt crystallization on the same rock specimens, and these point to lower erosive effects than salt weathering, as freeze–thaw can provoke catastrophic cracking. Wetting has shown strong damaging effects on some fine-grained clastic rocks. Erosive features have been reported for rain exposition and for some fountain settings albeit, in these field studies, it could be difficult to assess the contribution of pollutants transported by water (this assessment could have meaningful implications for stone conservation, especially in fountain settings). Water also interacts with stone constituents, namely sulfides and soluble salts, releasing substances that could impact those stones. Sulfides are a relatively frequent issue for slates and granites, and our observations suggest that for this last rock type, this issue is mostly associated with the presence of enclaves and, hence, avoiding the surface exposition of such enclaves could solve the problem.