As a green remediation technology for complete remediation of contaminated soil, the combination of easily recoverable adsorbents and washing still faces challenges such as low remediation efficiency and unclear remediation mechanisms. Hence, the bis Schiff base functional group comprising sulfhydryl groups was loaded into the UiO-66 calcium alginate spheres (UiO-66-AMB-ACPs) to obtain efficient selective adsorption. The results of response surface optimization showed that the maximum removal of Pb and Cd from soil reached 69.73% and 82.63% by the combination of UiO-66-AMB-ACPs with acetic acid, of which about 95.55% and 60.31% were attributed to the adsorption. Factor interaction analysis demonstrated that solid-liquid ratio combined with either adsorbent dosage or acetic acid concentration significantly affected Cd adsorption rates. In the above system, Schiff bases,-SH, and carboxylic acids in UiO-66-AMB-ACPs compete for the Pb and Cd captured by acetic acid through chelation, ion exchange, and complexation, which assisted in maintaining the high desorption rate to further enhance the resolution process of acid-soluble and reduced Pb and Cd. The release of free acetic acid will again participate in the resolution of heavy metals, thus constituting an internal cycle of acetic acid. UiO-66-AMB-ACPs were maintained in a stable state during each of the 18 cycles. The remediated soil retained most of the plant nutrients, while the mobility of residual heavy metals was greatly inhibited. This technique showed promise for the total removal and recovery of Pb and Cd from contaminated soils with low damage and short time while immobilizing the residual heavy metals.

Perlite is a volcanic glass that, under thermal treatment, expands, producing a highly porous and lightweight granular material which finds application in the construction, horticulture, insulation and other industrial sectors. Proper control of the feed properties and the expansion conditions allows the production of purpose-oriented grades, while the primary evaluation of its appropriateness for use in each sector is performed by the proper characterization of relevant physical, thermal or/and mechanical properties. However, due to its extreme fineness, low density, and friability, most of the available characterization methods either fail in testing or provide erroneous results, while for certain properties of interest, a method is still missing. As a consequence, the way towards the evaluation of the material is rife with uncertainties, while a well-defined methodology for the characterization of the critical properties is of practical importance towards the establishment of a pathway for its proper analysis and assessment. This article presents the available methodology for determining the main properties of interest, i.e., the size and density, water repellency/absorption and oil absorption, the microstructural composition, crushing and abrasion resistance and isostatic crushing strength, and also sampling and size reduction processes. The issues raised by the application of existing methods are analyzed and discussed, ending up to a proper methodology for the characterization of each property, based on the long-term experience of the Perlite Institute. The study is supplemented by updated insights on ore genesis, physicochemical properties, mineralogical composition and the expansion mechanism, as background information for the sufficient comprehension of the nature and properties of perlite.